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Soft gluons and hard scales in QCD : Heavy quarks at finite and all orders
Eynck, Tim Oliver
The strong interaction of elementary particles is described by Quantum Chromodynamics (QCD). Utilizing this theory to describe and predict experimental data requires a number of concepts and techniques. Three of these, namely factorization, resummation and numerical phase space integration, are
Energy Technology Data Exchange (ETDEWEB)
Moch, S.
We review the status of QCD at hadron colliders with emphasis on precision predictions and the latest theoretical developments for cross sections calculations to higher orders. We include an overview of our current information on parton distributions and discuss various Standard Model reactions such as W{sup {+-}}/Z-boson, Higgs boson or top quark production. (orig.)
Hard And Soft QCD Physics In ATLAS
Directory of Open Access Journals (Sweden)
Adomeit Stefanie
Full Text Available Hard and soft QCD results using proton-proton collisions recorded with the ATLAS detector at the LHC are reported. Charged-particle distributions and forward-backward correlations have been studied in low-luminosity minimum bias data taken at centre-of-mass energies of √s = 0.9, 2.36 and 7 TeV. Recent measurements on underlying event characteristics using charged-particle jets are also presented. The results are tested against various phenomenological soft QCD models implemented in Monte-Carlo generators. A summary of hard QCD measurements involving high transverse momentum jets is also given. Inclusive jet and dijet cross-sections have been measured at a centre-of-mass energy of 7 TeV and are compared to expectations based on NLO pQCD calculations corrected for non-perturbative effects as well as to NLO Monte Carlo predictions. Recent studies exploiting jet substructure techniques to identify hadronic decays of boosted massive particles are reported.
Hard scattering and QCD Fundamentals at RHIC
Tannenbaum, M J
In 1998, at the 4th QCD workshop, Rolf Baier asked me whether jets could be measured in Au+Au collisions because he had a prediction of a QCD medium-effect (energy loss via soft gluon radiation induced by multiple scattering) on color-charged partons traversing a hot-dense-medium composed of screened color-charges. I reviewed the possibilities in a talk explaining that there was a general consensus that for Au+Au central collisions at $\\sqrt{s_{NN}}=200$ GeV, leading particles are the only way to find jets because of the large particle density. The good news was that hard-scattering in p-p collisions was originally observed by the method of leading particles and that these techniques could be used to study hard-scattering and jets in Au+Au collisions. Notably, I described ``How everything you want to know about jets can be found using 2-particle correlations''. In fact, the predicted ``jet quenching'' and other new phenomena were discovered by this method. However, this past year, I had to soften the statemen...
Energy Technology Data Exchange (ETDEWEB)
Sommer, Rainer [DESY, Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
The principles of scale setting in lattice QCD as well as the advantages and disadvantages of various commonly used scales are discussed. After listing criteria for good scales, I concentrate on the main presently used ones with an emphasis on scales derived from the Yang-Mills gradient flow. For these I discuss discretisation errors, statistical precision and mass effects. A short review on numerical results also brings me to an unpleasant disagreement which remains to be explained.
Hard scattering in high-energy QCD
Mangano, Michelangelo L
I review the recent results in the field of QCD at high energy presented to this Conference. In particular, I will concentrate on measurements of $\\as$ from studies of event structures and jet rates, jet production in hadronic collisions, and heavy quark production.
Early Run 2 Hard QCD Results from the ATLAS Collaboration
AUTHOR|(INSPIRE)INSPIRE-00286920; The ATLAS collaboration
We provide an overview of hard QCD results based on data collected with the ATLAS detector in proton-proton collision at $\\sqrt{s}=13$~TeV at the Large Hadron Collider. The production of high transverse momentum jets, photons and photon-pairs were studied; the inclusive jet cross section is found to agree well with the prediction of perturbative QCD calculations performed at next-to-leading accuracy. The production cross sections for W and Z bosons in their $e$ and $\\mu$ decays was measured; in general, agreement is found with the expectation of next-to-next-to leading order QCD calculations and interesting sensitivities to the proton structure functions are already observed. The top production cross sections were measured in different top decay channels and found to agree with the state of the art QCD predictions.
Tests of hard and soft QCD with $e^{+}e^{-}$ Annihilation Data
Kluth, S
Experimental tests of QCD predictions for event shape distributions combining contributions from hard and soft processes are discussed. The hard processes are predicted by perturbative QCD calculations. The soft processes cannot be calculated directly using perturbative QCD, they are treated by a power correction model based on the analysis of infrared renormalons. Furthermore, an analysis of the gauge structure of QCD is presented using fits of the colour factors within the same combined QCD predictions.
Pion Form Factor in Chiral Limit of Hard-Wall AdS/QCD Model
Energy Technology Data Exchange (ETDEWEB)
Anatoly Radyushkin; Hovhannes Grigoryan
We develop a formalism to calculate form factor and charge density distribution of pion in the chiral limit using the holographic dual model of QCD with hard-wall cutoff. We introduce two conjugate pion wave functions and present analytic expressions for these functions and for the pion form factor. They allow to relate such observables as the pion decay constant and the pion charge electric radius to the values of chiral condensate and hard-wall cutoff scale. The evolution of the pion form factor to large values of the momentum transfer is discussed, and results are compared to existing experimental data.
Hard QCD and hadronic final state at HERA
Valkárová, Alice
The production of inclusive jets, dijets and trijets was investigated with the high statistics HERA II DIS data. The H1 experiment has determined the corresponding cross sections with improved experimental precision and sophisticated method of unfolding, compared to previous measurements. The results were compared with NLO QCD and NNLO QCD calculations for the first time. Signals of QCD instanton-induced processes were searched for in neutral current deep-inelastic scattering with high momentum transfer Q2 by H1 collaboration. Compared to earlier publications, the limits were improved by an order of magnitude. A search for a narrow baryonic state in the p KS0 and p ¯KS0 system has been performed with the ZEUS detector. Measurements with the ZEUS data in DIS of isolated photons were reported, including studies of kinematic variables sensitive to the event dynamics. The measurements were compared to MC models and to theoretical calculations based on kt factorisation QCD approach.
Basic Properties of QCD: the Lagrangian, the running coupling, asymptotic freedom and colour confinement. Examples of perturbative calculations in electron- positron physics (total cross sections and event) Parton branching approach will be used to derive the evolution equations for hadron structure functions Comarison with data on deep inelastic scattering and jet production will be for hadron structure functions and jet fragmentation functions
The renormalization scale-setting problem in QCD
Energy Technology Data Exchange (ETDEWEB)
Wu, Xing-Gang [Chongqing Univ. (China); Brodsky, Stanley J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Mojaza, Matin [SLAC National Accelerator Lab., Menlo Park, CA (United States); Univ. of Southern Denmark, Odense (Denmark)
A key problem in making precise perturbative QCD predictions is to set the proper renormalization scale of the running coupling. The conventional scale-setting procedure assigns an arbitrary range and an arbitrary systematic error to fixed-order pQCD predictions. In fact, this ad hoc procedure gives results which depend on the choice of the renormalization scheme, and it is in conflict with the standard scale-setting procedure used in QED. Predictions for physical results should be independent of the choice of the scheme or other theoretical conventions. We review current ideas and points of view on how to deal with the renormalization scale ambiguity and show how to obtain renormalization scheme- and scale-independent estimates. We begin by introducing the renormalization group (RG) equation and an extended version, which expresses the invariance of physical observables under both the renormalization scheme and scale-parameter transformations. The RG equation provides a convenient way for estimating the scheme- and scale-dependence of a physical process. We then discuss self-consistency requirements of the RG equations, such as reflexivity, symmetry, and transitivity, which must be satisfied by a scale-setting method. Four typical scale setting methods suggested in the literature, i.e., the Fastest Apparent Convergence (FAC) criterion, the Principle of Minimum Sensitivity (PMS), the Brodsky–Lepage–Mackenzie method (BLM), and the Principle of Maximum Conformality (PMC), are introduced. Basic properties and their applications are discussed. We pay particular attention to the PMC, which satisfies all of the requirements of RG invariance. Using the PMC, all non-conformal terms associated with the β-function in the perturbative series are summed into the running coupling, and one obtains a unique, scale-fixed, scheme-independent prediction at any finite order. The PMC provides the principle underlying the BLM method, since it gives the general rule for extending
Soft-gluon resolution scale in QCD evolution equations
Directory of Open Access Journals (Sweden)
F. Hautmann
Full Text Available QCD evolution equations can be recast in terms of parton branching processes. We present a new numerical solution of the equations. We show that this parton-branching solution can be applied to analyze infrared contributions to evolution, order-by-order in the strong coupling αs, as a function of the soft-gluon resolution scale parameter. We examine the cases of transverse-momentum ordering and angular ordering. We illustrate that this approach can be used to treat distributions which depend both on longitudinal and on transverse momenta.
Nonlinear dynamics of soft boson collective excitations in hot QCD plasma II: plasmon -- hard-particle scattering and energy losses
Markov, Y. A.; Markova, M. A.; Vall, A. N.
In a general line with our first work (Ann.Phys.302(2002),172; hep-ph/0207316), within hard thermal loop approximation a general theory of the scattering for an arbitrary number of colorless plasmons off hard thermal particles of hot QCD-medium is considered. Using generalized Tsytovich correspondence principle, a connection between matrix elements of the scattering processes and a certain effective current, generating these processes is established. The iterative procedure of calculation of ...
Pire, Bernard
We review the theory of hard exclusive scattering in Quantum Chromodynamics. After recalling the classical counting rules which describe the leading scale dependence of form factors and exclusive cross-sections at fixed angle, the pedagogical example of the pion form factor is developped in some detail in order to show explicitely what factorization means in the QCD framework. The picture generalizes to many hard reactions which are at the heart of the ELFE project. We briefly present the con...
Determination of the QCD scale parameter. Lambda. sub MS with QCD cascade on the basis of the next-to-leading logarithmic approximation
Energy Technology Data Exchange (ETDEWEB)
Abe, K. (Tohoku Univ., Sendai (Japan). Dept. of Physics); Amako, K.; Arai, Y.; Fukawa, M.; Fukushima, Y.; Haidt, D.; Ishihara, N.; Kamitani, T.; Kanzaki, J.; Kondo, T.; Matsui, T.; Odaka, S.; Ogawa, K.; Ohama, T.; Sakamoto, H.; Sakuda, M.; Shirai, J.; Sumiyoshi, T.; Takasaki, F.; Tsuboyama, T.; Uehara, S.; Unno, Y.; Watase, Y.; Yamada, Y. (National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)); Asano, Y.; Koseki, T.; Mori, S.; Sakano, M.; Shirakata, M.; Takada, Y.; Yonezawa, Y. (Tsukuba Univ., Sakura, Ibaraki (Japan). Inst. of Applied Physics); Chiba, M.; Fukui, T.; Hirose, T.; Minami, M.; Narita, Y.; Oyama, T.; Saito, H.; Utsumi, M.; Wakai, M.; Watanabe, T.; Yabuki, F.; Yamagata, T. (Tokyo Metropolitan Univ. (Japan). Dept. of Physics); Chiba, Y.; Hayashibara, I.; Ohsugi, T.; Taketani, A.; Tanaka, R.; Terunuma, N. (Hiroshima Univ. (Japan)); Daigo, M. (Wakayama Medical Coll. (Japan)); Emura, T. (Tokyo Univ. of Agriculture and Technology, Koganei (Japan)); Haba, J.; Kane; VENUS Collaboration
The relative production ratio of 3-jet events to the total number of hadronic events was studied in e{sup +}e{sup -} annihilations at centre-of-mass energies between 54 and 61.4 GeV. The QCD scale parameter has been determined to be {Lambda}{sub MS}=254{sub -47}{sup +55}{plus minus}56 MeV on the basis of a QCD cascade with the next-to-leading logarithmic approximation. (orig.).
QCD jet evolution at high and low scales
Energy Technology Data Exchange (ETDEWEB)
Winter, Jan-Christopher
The formation of jets of hadrons is a basic manifestation of the strong interaction as explored in and measured by high-energy physics collider experiments. Jets appear as narrow cones of particles that yield energy deposits in the calorimeters of the detectors. Invoking Quantum Chromodynamics (QCD) - the underlying theory of the strong interaction and one of the four fundamental forces of nature - leads to predictions and models, which describe the initiation, evolution and hadronization of jets. Good precision and quality of theoretical results and approaches to jet physics are necessary and thus vital for the successful accomplishment of the challenges in elementary particle physics, the current (e.g. proton-antiproton collisions at the Fermilab Tevatron) as well as the upcoming ones (e.g. proton-proton collisions at the CERN Large Hadron Collider). In this thesis various aspects of the eld of QCD jet physics are addressed, all of which under the common denominator of validating and improving the simulations computed by Monte Carlo event generators, in particular that of SHERPA, which has been developed in Dresden. Therefor the following questions were investigated, and, respective results have been achieved: - The method of merging tree-level matrix elements with parton showers has been critically verified against other merging approaches for inclusive gauge boson production at Tevatron and LHC energies. Also, the genesis of dibosons has been studied in comparison to next-to-leading order predictions in the strong coupling and other Monte Carlo generator approaches. These studies triggered improvements of the method of SHERPA, and, finally, important results have been derived, proving its relevance for ongoing and future experimental analyses. In its present form this method hence exhibits a very modern, state-of-the-art, approach to multijet production and evolution in high-energy particle collisions. - A new shower model based on QCD colour dipoles and their
Setting the Renormalization Scale in QCD: The Principle of Maximum Conformality
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; Di Giustino, Leonardo; /SLAC
A key problem in making precise perturbative QCD predictions is the uncertainty in determining the renormalization scale {mu} of the running coupling {alpha}{sub s}({mu}{sup 2}): The purpose of the running coupling in any gauge theory is to sum all terms involving the {beta} function; in fact, when the renormalization scale is set properly, all non-conformal {beta} {ne} 0 terms in a perturbative expansion arising from renormalization are summed into the running coupling. The remaining terms in the perturbative series are then identical to that of a conformal theory; i.e., the corresponding theory with {beta} = 0. The resulting scale-fixed predictions using the 'principle of maximum conformality' (PMC) are independent of the choice of renormalization scheme - a key requirement of renormalization group invariance. The results avoid renormalon resummation and agree with QED scale-setting in the Abelian limit. The PMC is also the theoretical principle underlying the BLM procedure, commensurate scale relations between observables, and the scale-setting method used in lattice gauge theory. The number of active flavors nf in the QCD {beta} function is also correctly determined. We discuss several methods for determining the PMC/BLM scale for QCD processes. We show that a single global PMC scale, valid at leading order, can be derived from basic properties of the perturbative QCD cross section. The elimination of the renormalization scheme ambiguity using the PMC will not only increase the precision of QCD tests, but it will also increase the sensitivity of collider experiments to new physics beyond the Standard Model.
Universal Off-Equilibrium Scaling of Critical Cumulants in the QCD Phase Diagram.
Mukherjee, Swagato; Venugopalan, Raju; Yin, Yi
Exploiting the universality between the QCD critical point and the three-dimensional Ising model, closed form expressions derived for nonequilibrium critical cumulants on the crossover side of the critical point reveal that they can differ in both magnitude and sign from equilibrium expectations. We demonstrate here that key elements of the Kibble-Zurek framework of nonequilibrium phase transitions can be employed to describe the dynamics of these critical cumulants. Our results suggest that observables sensitive to critical dynamics in heavy-ion collisions should be expressible as universal scaling functions, thereby providing powerful model-independent guidance in searches for the QCD critical point.
Setting the renormalization scale in QCD: The principle of maximum conformality
DEFF Research Database (Denmark)
Brodsky, S. J.; Di Giustino, L.
A key problem in making precise perturbative QCD predictions is the uncertainty in determining the renormalization scale mu of the running coupling alpha(s)(mu(2)). The purpose of the running coupling in any gauge theory is to sum all terms involving the beta function; in fact, when the renormali...
Hard Break-Up of Two-Nucleons and QCD Dynamics of NN Interaction
Sargsian, Misak
We discus recent developments in theory of high energy two-body break-up of few-nucleon systems. The characteristics of these reactions are such that the hard two-body quasielastic subprocess can be clearly separated from the accompanying soft subprocesses. We discuss in details the hard rescattering model (HRM) in which hard photodisintegration develops in two stages. At first, photon knocks-out an energetic quark which rescatters subsequently with a quark of the other nucleon. The latter provides a mechanism of sharing the initial high momentum of the photon between two outgoing nucleons. This final state hard rescattering can be expressed through the hard NN scattering amplitude. Within HRM we discuss hard break-up reactions involving D and 3He targets and demonstrate how these reactions are sensitive to the dynamics of hard pn and pp interaction. Another development of HRM is the prediction of new helicity selection mechanism for hard two-body reactions, which was apparently confirmed in the recent JLab experiment.
TMD Evolution at Moderate Hard Scales
Energy Technology Data Exchange (ETDEWEB)
Rogers, Ted [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Old Dominion Univ., Norfolk, VA (United States); Collins, John C. [Pennsylvania State Univ., University Park, PA (United States)
We summarize some of our recent work on non-perturbative transverse momentum dependent (TMD) evolution, emphasizing aspects that are necessary for dealing with moderately low scale processes like semi-inclusive deep inelastic scattering.
Spontaneous chiral symmetry breaking in QCD:a finite-size scaling study on the lattice
Giusti, Leonardo; Giusti, Leonardo; Necco, Silvia
Spontaneous chiral symmetry breaking in QCD with massless quarks at infinite volume can be seen in a finite box by studying, for instance, the dependence of the chiral condensate from the volume and the quark mass. We perform a feasibility study of this program by computing the quark condensate on the lattice in the quenched approximation of QCD at small quark masses. We carry out simulations in various topological sectors of the theory at several volumes, quark masses and lattice spacings by employing fermions with an exact chiral symmetry, and we focus on observables which are infrared stable and free from mass-dependent ultraviolet divergences. The numerical calculation is carried out with an exact variance-reduction technique, which is designed to be particularly efficient when spontaneous symmetry breaking is at work in generating a few very small low-lying eigenvalues of the Dirac operator. The finite-size scaling behaviour of the condensate in the topological sectors considered agrees, within our stati...
DEFF Research Database (Denmark)
Bechi, Jacopo
This paper focuses on some issues about condensates and renormalization in AdS/QCD models. In particular we consider the consistency of the AdS/QCD approach for scale dependent quantities as the chiral condensate questioned in some recent papers and the 4D meaning of the 5D cosmological constant...... in a model in which the QCD is dual to a 5D gravity theory. We will be able to give some arguments that the cosmological constant is related to the QCD gluon condensate....
Quantum Phase Transitions and New Scales in QCD-Like Theories
Energy Technology Data Exchange (ETDEWEB)
Unsal, Mithat
It is commonly believed that in confining vector-like gauge theories the center and chiral symmetry realizations are parametrically entangled, and if phase transitions occur, they must take place around the strong scale {Lambda}{sup -1} of the gauge theory. We demonstrate that (non-thermal) vector-like theories formulated on R{sup 3} x S{sup 1} where S{sup 1} is a spatial circle exhibit new dynamical scales and new phenomena. There are chiral phase transitions taking place at {Lambda}{sup -1}/N{sub c} in the absence of any change in center symmetry. {Lambda}{sup -1}/N{sub c}, invisible in (planar) perturbation theory, is also the scale where abelian versus non-abelian confinement regimes meet. Large N{sub c} volume independence (a working Eguchi-Kawai reduction) provides new insights and independently confirms the existence of these scales. We show that certain phases and scales are outside the reach of holographic (supergravity) modeling of QCD.
Hyper-scaling relations in the conformal window from dynamic AdS/QCD
Evans, Nick; Scott, Marc
Dynamic AdS/QCD is a holographic model of strongly coupled gauge theories with the dynamics included through the running anomalous dimension of the quark bilinear, γ. We apply it to describe the physics of massive quarks in the conformal window of SU(Nc) gauge theories with Nf fundamental flavors, assuming the perturbative two-loop running for γ. We show that to find regular, holographic renormalization group flows in the infrared, the decoupling of the quark flavors at the scale of the mass is important, and enact it through suitable boundary conditions when the flavors become on shell. We can then compute the quark condensate and the mesonic spectrum (Mρ,Mπ,Mσ) and decay constants. We compute their scaling dependence on the quark mass for a number of examples. The model matches perturbative expectations for large quark mass and naïve dimensional analysis (including the anomalous dimensions) for small quark mass. The model allows study of the intermediate regime where there is an additional scale from the running of the coupling, and we present results for the deviation of scalings from assuming only the single scale of the mass.
A scaling rule of indentation hardness of semiconductors
Yonenaga, Ichiro; Suzuki, Takayoshi
We report a scaling rule of the indentation hardness of semiconductor crystals from room temperature to their melting. The Vickers hardness of fifteen semiconductors, Si, Ge, SiC, AlN, GaN, GaP, GaAs, GaSb, InP, InAs, InSb, ZnO, ZnSe, ZnTe and CdTe, has been investigated from room temperature to their melting points. The temperature dependences of the hardness H v of eleven of these semiconductors, namely those with a cubic structure, obey a universal relationship when H v and the temperature T are scaled respectively by the shear modulus G and by G b ^3 / k _B, with b being the magnitude of the Burgers vector and k B the Boltzmann constant. The scaling rule is the same as that found for the temperature dependence of the critical shear stress τ c for the 111 slip system. The result leads a link between hardness and macroscopic yielding (dislocation motion). The relationshipH v = (70 ˜ 100) τ c is deduced for the cubic semiconductors is about ten times as large as the value for metals.
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins
I review a number of topics where conventional wisdom in hadron physics has been challenged. For example, hadrons can be produced at large transverse momentum directly within a hard higher-twist QCD subprocess, rather than from jet fragmentation. Such 'direct' processes can explain the deviations from perturbative QCD predictions in measurements of inclusive hadron cross sections at fixed x{sub T} = 2p{sub T}/{radical}s, as well as the 'baryon anomaly', the anomalously large proton-to-pion ratio seen in high centrality heavy ion collisions. Initial-state and final-state interactions of the struck quark, the soft-gluon rescattering associated with its Wilson line, lead to Bjorken-scaling single-spin asymmetries, diffractive deep inelastic scattering, the breakdown of the Lam-Tung relation in Drell-Yan reactions, as well as nuclear shadowing and antishadowing. The Gribov-Glauber theory predicts that antishadowing of nuclear structure functions is not universal, but instead depends on the flavor quantum numbers of each quark and antiquark, thus explaining the anomalous nuclear dependence measured in deep-inelastic neutrino scattering. Since shadowing and antishadowing arise from the physics of leading-twist diffractive deep inelastic scattering, one cannot attribute such phenomena to the structure of the nucleus itself. It is thus important to distinguish 'static' structure functions, the probability distributions computed from the square of the target light-front wavefunctions, versus 'dynamical' structure functions which include the effects of the final-state rescattering of the struck quark. The importance of the J = 0 photon-quark QCD contact interaction in deeply virtual Compton scattering is also emphasized. The scheme-independent BLM method for setting the renormalization scale is discussed. Eliminating the renormalization scale ambiguity greatly improves the precision of QCD predictions and increases the sensitivity of
Degeneracy relations in QCD and the equivalence of two systematic all-orders methods for setting the renormalization scale
Directory of Open Access Journals (Sweden)
Huan-Yu Bi
Full Text Available The Principle of Maximum Conformality (PMC eliminates QCD renormalization scale-setting uncertainties using fundamental renormalization group methods. The resulting scale-fixed pQCD predictions are independent of the choice of renormalization scheme and show rapid convergence. The coefficients of the scale-fixed couplings are identical to the corresponding conformal series with zero β-function. Two all-orders methods for systematically implementing the PMC-scale setting procedure for existing high order calculations are discussed in this article. One implementation is based on the PMC-BLM correspondence (PMC-I; the other, more recent, method (PMC-II uses the Rδ-scheme, a systematic generalization of the minimal subtraction renormalization scheme. Both approaches satisfy all of the principles of the renormalization group and lead to scale-fixed and scheme-independent predictions at each finite order. In this work, we show that PMC-I and PMC-II scale-setting methods are in practice equivalent to each other. We illustrate this equivalence for the four-loop calculations of the annihilation ratio Re+e− and the Higgs partial width Γ(H→bb¯. Both methods lead to the same resummed ('conformal' series up to all orders. The small scale differences between the two approaches are reduced as additional renormalization group {βi}-terms in the pQCD expansion are taken into account. We also show that special degeneracy relations, which underly the equivalence of the two PMC approaches and the resulting conformal features of the pQCD series, are in fact general properties of non-Abelian gauge theory.
Degeneracy relations in QCD and the equivalence of two systematic all-orders methods for setting the renormalization scale
Bi, Huan-Yu; Wu, Xing-Gang; Ma, Yang; Ma, Hong-Hao; Brodsky, Stanley J.; Mojaza, Matin
The Principle of Maximum Conformality (PMC) eliminates QCD renormalization scale-setting uncertainties using fundamental renormalization group methods. The resulting scale-fixed pQCD predictions are independent of the choice of renormalization scheme and show rapid convergence. The coefficients of the scale-fixed couplings are identical to the corresponding conformal series with zero β-function. Two all-orders methods for systematically implementing the PMC-scale setting procedure for existing high order calculations are discussed in this article. One implementation is based on the PMC-BLM correspondence (PMC-I); the other, more recent, method (PMC-II) uses the Rδ-scheme, a systematic generalization of the minimal subtraction renormalization scheme. Both approaches satisfy all of the principles of the renormalization group and lead to scale-fixed and scheme-independent predictions at each finite order. In this work, we show that PMC-I and PMC-II scale-setting methods are in practice equivalent to each other. We illustrate this equivalence for the four-loop calculations of the annihilation ratio Re+e- and the Higgs partial width Γ (H → b b bar). Both methods lead to the same resummed ('conformal') series up to all orders. The small scale differences between the two approaches are reduced as additional renormalization group {βi }-terms in the pQCD expansion are taken into account. We also show that special degeneracy relations, which underly the equivalence of the two PMC approaches and the resulting conformal features of the pQCD series, are in fact general properties of non-Abelian gauge theory.
The Light-Front Schrödinger Equation and Determination of the Perturbative QCD Scale from Color Confinement
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); de Teramond, Guy F. [Univ. of Costa Rica, San Pedro (Costa Rica); Deur, Alexandre P. [Jefferson La.b, Newport News, VA (United States); Dosch, Hans G. [Institut fur Theoretische Physik, Heidelberg (Germany)
The valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a relativistic equation of motion with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. If one requires that the effective action which underlies the QCD Lagrangian remains conformally invariant and extends the formalism of de Alfaro, Fubini and Furlan to light front Hamiltonian theory, the potential U has a unique form of a harmonic oscillator potential, and a mass gap arises. The result is a nonperturbative relativistic light-front quantum mechanical wave equation which incorporates color confinement and other essential spectroscopic and dynamical features of hadron physics, including a massless pion for zero quark mass and linear Regge trajectories with the same slope in the radial quantum number n and orbital angular momentum L. Only one mass parameter κ appears. Light-front holography thus provides a precise relation between the bound-state amplitudes in the fifth dimension of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. We also show how the mass scale κ underlying confinement and hadron masses determines the scale Λ{ovr MS} controlling the evolution of the perturbative QCD coupling. The relation between scales is obtained by matching the nonperturbative dynamics, as described by an effective conformal theory mapped to the light-front and its embedding in AdS space, to the perturbative QCD regime computed to four-loop order. The result is an effective coupling defined at all momenta. The predicted value Λ{ovr MS}=0.328±0.034 GeV is in agreement with the world average 0.339±0.010 GeV. The analysis applies to any renormalization scheme.
Scale dependence and renormalon-inspired resummations for some QCD observables
Energy Technology Data Exchange (ETDEWEB)
Mirjalili, A
Since the advent of Quantum Field Theory (QFT) in the late 1940's, perturbation theory has become one of the most successful means of extracting phenomenologically useful information from QFT. In the ever-increasing enthusiasm for new phenomenological predictions, the mechanics of perturbation theory itself have taken a back seat. It is in this light that this thesis aims to investigate some of the more fundamental properties of perturbation theory. In the first part of this thesis, we develop the idea, suggested by C.J.Maxwell, that at any given order of Feynman diagram calculation for a QCD observable all renormalization group (RG)-predictable terms should be resummed to all-orders. This 'complete' RG-improvement (CORGI) serves to separate the perturbation series into infinite subsets of terms which when summed are renormalization scheme (RS)-invariant. Crucially all ultraviolet logarithms involving the dimensionful parameter, Q, on which the observable depends are resummed, thereby building the correct Q-dependence. We extend this idea, and show for moments of leptoproduction structure functions that all dependence on the renormalization and factorization scales disappears provided that all the ultraviolet logarithms involving the physical energy scale Q are completely resummed. The approach is closely related to Grunberg's method of Effective Charges. In the second part, we perform an all-orders resummation of the QCD Adler D-function for the vector correlator, in which the portion of perturbative coefficients containing the leading power of b, the first beta-function coefficient, is resummed to all-orders. To avoid a renormalization scale dependence when we match the resummation to the exactly known next-to-leading order (NLO), and next-NLO (NNLO) we employ the Complete Renormalization Group Improvement (CORGI) approach removing all dependence on the renormalization scale. We can also obtain fixed-order CORGI results. Including suitable
CERN. Geneva
Perturbative QCD is the general theoretical framework for describing hard scattering processes yielding multiparticle production at hadron colliders. In these lectures, we shall introduce fundamental features of perturbative QCD and describe its application to several high energy collider processes, including jet production in electron-positron annihilation, deep inelastic scattering, Higgs boson and gauge boson production at the LHC.
Nanometer Scale Hard/Soft Bilayer Magnetic Antidots.
Béron, Fanny; Kaidatzis, Andreas; Velo, Murilo F; Arzuza, Luis C C; Palmero, Ester M; Del Real, Rafael P; Niarchos, Dimitrios; Pirota, Kleber R; García-Martín, José Miguel
The effect of arrays of nanometer scale pores on the magnetic properties of thin films has been analyzed. Particularly, we investigated the influence of the out-of-plane magnetization component created by the nanopores on the in-plane magnetic behavior of patterned hard/soft magnetic thin films in antidot morphology. Its influence on the coupling in Co/Py bilayers of few tens of nanometer thick is compared for disordered and ordered antidots of 35-nm diameter. The combination of magneto-optical Kerr effect (MOKE) and first-order reversal curve (FORC) technique allows probing the effects of the induced perpendicular magnetization component on the bilayer magnetic behavior, while magnetic force microscopy (MFM) is used to image it. We found that ordered antidots yield a stronger out-of-plane component than disordered ones, influencing in a similar manner the hard layer global in-plane magnetic behavior if with a thin or without soft layer. However, its influence changes with a thicker soft layer, which may be an indication of a weaker coupling.
Meyer, C; The ATLAS collaboration
The ATLAS collaboration has performed studies of a wide range of QCD phenomena, from soft particle to hard photon and jet production. Recent soft-QCD measurements include studies of underlying event and vector meson production. Differential measurements of inclusive and dijet production provide stringent tests of high-order QCD predictions and provide input for determination of parton density functions. Measurements of isolated inclusive and di-photons cross sections for high transverse momentum photons test theoretical predictions of perturbative QCD and constrain parton density functions. An overview of these results is given.
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC
I discuss a number of novel topics in QCD, including the use of the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. In particular, there is an exact correspondence between the fifth-dimension coordinate z of AdS space and a specific impact variable {zeta} which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. I also discuss a number of novel phenomenological features of QCD. Initial- and final-state interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, and anomalous heavy quark effects. The presence of direct higher-twist processes where a proton is produced in the hard subprocess can explain the large proton-to-pion ratio seen in high centrality heavy ion collisions.
Setting the renormalization scale in pQCD: Comparisons of the principle of maximum conformality with the sequential extended Brodsky-Lepage-Mackenzie approach
Energy Technology Data Exchange (ETDEWEB)
Ma, Hong -Hao [Chongqing Univ., Chongqing (People' s Republic of China); Wu, Xing -Gang [Chongqing Univ., Chongqing (People' s Republic of China); Ma, Yang [Chongqing Univ., Chongqing (People' s Republic of China); Brodsky, Stanley J. [Stanford Univ., Stanford, CA (United States); Mojaza, Matin [KTH Royal Inst. of Technology and Stockholm Univ., Stockholm (Sweden)
A key problem in making precise perturbative QCD (pQCD) predictions is how to set the renormalization scale of the running coupling unambiguously at each finite order. The elimination of the uncertainty in setting the renormalization scale in pQCD will greatly increase the precision of collider tests of the Standard Model and the sensitivity to new phenomena. Renormalization group invariance requires that predictions for observables must also be independent on the choice of the renormalization scheme. The well-known Brodsky-Lepage-Mackenzie (BLM) approach cannot be easily extended beyond next-to-next-to-leading order of pQCD. Several suggestions have been proposed to extend the BLM approach to all orders. In this paper we discuss two distinct methods. One is based on the "Principle of Maximum Conformality" (PMC), which provides a systematic all-orders method to eliminate the scale and scheme ambiguities of pQCD. The PMC extends the BLM procedure to all orders using renormalization group methods; as an outcome, it significantly improves the pQCD convergence by eliminating renormalon divergences. An alternative method is the "sequential extended BLM" (seBLM) approach, which has been primarily designed to improve the convergence of pQCD series. The seBLM, as originally proposed, introduces auxiliary fields and follows the pattern of the β0-expansion to fix the renormalization scale. However, the seBLM requires a recomputation of pQCD amplitudes including the auxiliary fields; due to the limited availability of calculations using these auxiliary fields, the seBLM has only been applied to a few processes at low orders. In order to avoid the complications of adding extra fields, we propose a modified version of seBLM which allows us to apply this method to higher orders. As a result, we then perform detailed numerical comparisons of the two alternative scale-setting approaches by investigating their predictions for the annihilation cross section ratio R
The QCD mass gap and quark deconfinement scales as mass bounds in strong gravity
Burikham, Piyabut; Harko, Tiberiu; Lake, Matthew J.
Though not a part of mainstream physics, Salam's theory of strong gravity remains a viable effective model for the description of strong interactions in the gauge singlet sector of QCD, capable of producing particle confinement and asymptotic freedom, but not of reproducing interactions involving SU(3) color charge. It may therefore be used to explore the stability and confinement of gauge singlet hadrons, though not to describe scattering processes that require color interactions. It is a two-tensor theory of both strong interactions and gravity, in which the strong tensor field is governed by equations formally identical to the Einstein equations, apart from the coupling parameter, which is of order 1 {GeV}^{-1}. We revisit the strong gravity theory and investigate the strong gravity field equations in the presence of a mixing term which induces an effective strong cosmological constant, Λ f. This introduces a strong de Sitter radius for strongly interacting fermions, producing a confining bubble, which allows us to identify Λ f with the `bag constant' of the MIT bag model, B ˜eq 2 × 10^{14} {g} {cm}^{-3}. Assuming a static, spherically symmetric geometry, we derive the strong gravity TOV equation, which describes the equilibrium properties of compact hadronic objects. From this, we determine the generalized Buchdahl inequalities for a strong gravity `particle', giving rise to upper and lower bounds on the mass/radius ratio of stable, compact, strongly interacting objects. We show, explicitly, that the existence of the lower mass bound is induced by the presence of Λ _f, producing a mass gap, and that the upper bound corresponds to a deconfinement phase transition. The physical implications of our results for holographic duality in the context of the AdS/QCD and dS/QCD correspondences are also discussed.
Scale Setting Using the Extended Renormalization Group and the Principle of Maximal Conformality: the QCD Coupling at Four Loops
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC; Wu, Xing-Gang; /SLAC /Chongqing U.
A key problem in making precise perturbative QCD predictions is to set the proper renormalization scale of the running coupling. The extended renormalization group equations, which express the invariance of physical observables under both the renormalization scale- and scheme-parameter transformations, provide a convenient way for estimating the scale- and scheme-dependence of the physical process. In this paper, we present a solution for the scale-equation of the extended renormalization group equations at the four-loop level. Using the principle of maximum conformality (PMC)/Brodsky-Lepage-Mackenzie (BLM) scale-setting method, all non-conformal {beta}{sub i} terms in the perturbative expansion series can be summed into the running coupling, and the resulting scale-fixed predictions are independent of the renormalization scheme. Different schemes lead to different effective PMC/BLM scales, but the final results are scheme independent. Conversely, from the requirement of scheme independence, one not only can obtain scheme-independent commensurate scale relations among different observables, but also determine the scale displacements among the PMC/BLM scales which are derived under different schemes. In principle, the PMC/BLM scales can be fixed order-by-order, and as a useful reference, we present a systematic and scheme-independent procedure for setting PMC/BLM scales up to NNLO. An explicit application for determining the scale setting of R{sub e{sup +}e{sup -}}(Q) up to four loops is presented. By using the world average {alpha}{sub s}{sup {ovr MS}}(MZ) = 0.1184 {+-} 0.0007, we obtain the asymptotic scale for the 't Hooft associated with the {ovr MS} scheme, {Lambda}{sub {ovr MS}}{sup 'tH} = 245{sub -10}{sup +9} MeV, and the asymptotic scale for the conventional {ovr MS} scheme, {Lambda}{sub {ovr MS}} = 213{sub -8}{sup +19} MeV.
NNLO QCD corrections to the Drell-Yan cross section in models of TeV-scale gravity
Energy Technology Data Exchange (ETDEWEB)
Ahmed, Taushif; Banerjee, Pulak; Dhani, Prasanna K.; Rana, Narayan [The Institute of Mathematical Sciences, Chennai, Tamil Nadu (India); Homi Bhabha National Institute, Mumbai (India); Kumar, M.C. [Indian Institute of Technology Guwahati, Department of Physics, Guwahati (India); Mathews, Prakash [Saha Institute of Nuclear Physics, Kolkata, West Bengal (India); Ravindran, V. [The Institute of Mathematical Sciences, Chennai, Tamil Nadu (India)
The first results on the complete next-to-next-to-leading order (NNLO) Quantum Chromodynamic (QCD) corrections to the production of di-leptons at hadron colliders in large extra dimension models with spin-2 particles are reported in this article. In particular, we have computed these corrections to the invariant mass distribution of the di-leptons taking into account all the partonic sub-processes that contribute at NNLO. In these models, spin-2 particles couple through the energy-momentum tensor of the Standard Model with the universal coupling strength. The tensorial nature of the interaction and the presence of both quark annihilation and gluon fusion channels at the Born level make it challenging computationally and interesting phenomenologically. We have demonstrated numerically the importance of our results at Large Hadron Collider energies. The two-loop corrections contribute an additional 10% to the total cross section. We find that the QCD corrections are not only large but also important to make the predictions stable under renormalisation and factorisation scale variations, providing an opportunity to stringently constrain the parameters of the models with a spin-2 particle. (orig.)
DEFF Research Database (Denmark)
Sannino, Francesco
We uncover a novel solution of the 't Hooft anomaly matching conditions for QCD. Interestingly in the perturbative regime the new gauge theory, if interpreted as a possible QCD dual, predicts the critical number of flavors above which QCD in the nonperturbative regime, develops an infrared stable...... fixed point. Remarkably this value is identical to the maximum bound predicted in the nonpertubative regime via the all-orders conjectured beta function for nonsupersymmetric gauge theories....
Energy Technology Data Exchange (ETDEWEB)
Bjorken, J.D.
New directions for exploring QCD at future high-energy colliders are sketched. These include jets within jets. BFKL dynamics, soft and hard diffraction, searches for disoriented chiral condensate, and doing a better job on minimum bias physics. The new experimental opportunities include electron-ion collisions at HERA, a new collider detector at the C0 region of the TeVatron, and the FELIX initiative at the LHC.
I. Hinchliffe
This is the written version of a set of lectures on perturbative QCD that were delivered to a mixed audience of young theorists and experimentalists in the course of the XXII International Meeting on Fundamental Physics. These notes are virtually a verbatim transcription of the lectures. The selection of topics is somewhat arbitrary, but two basic points are emphasized: the rationale behind QCD and how ongoing experiments, such as those taking place in LEP and HERA, contribute to our understa...
Cerci, Salim
Jets which are the signatures of quarks and gluons in the detector can be described by Quantum Chromodynamics (QCD) in terms of parton-parton scattering. Jets are abundantly produced at the LHC's high energy scales. Measurements of inclusive jets, dijets and multijets can be used to test perturbative QCD predictions and to constrain parton distribution functions (PDF), as well as to measure the strong coupling constant $\\alpha_{S}$. The measurements use the samples of proton-proton collisions collected with the CMS detector at the LHC at various center-of-mass energies of 7, 8 and 13 TeV.
Complete renormalization group improvement - avoiding factorization and renormalization scale dependence in QCD predictions
Energy Technology Data Exchange (ETDEWEB)
Maxwell, C.J. E-mail: firstname.lastname@example.com; Mirjalili, A. E-mail: email@example.com
For moments of leptoproduction structure functions we show that all dependence on the renormalization and factorization scales disappears provided that all the ultraviolet logarithms involving the physical energy scale Q are completely resummed. The approach is closely related to Grunberg's method of effective charges. A direct and simple method for extracting {lambda}{sub MS-bar} from experimental data is advocated.
Basics of QCD perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Soper, D.E. [Univ. of Oregon, Eugene, OR (United States). Inst. of Theoretical Science
This is an introduction to the use of QCD perturbation theory, emphasizing generic features of the theory that enable one to separate short-time and long-time effects. The author also covers some important classes of applications: electron-positron annihilation to hadrons, deeply inelastic scattering, and hard processes in hadron-hadron collisions. 31 refs., 38 figs.
QCD analysis of p-bar N->{gamma}*{pi} in the scaling limit
Energy Technology Data Exchange (ETDEWEB)
Pire, B. [CPhT, Ecole Polytechnique, F-91128 Palaiseau (France); Szymanowski, L. [Soltan Institute for Nuclear Studies, Warsaw (Poland) and Universite de Liege, B-4000 Liege (Belgium)]. E-mail: email@example.com
We study the scaling regime of nucleon-antinucleon annihilation into a deeply virtual photon and a meson, p-bar N->{gamma}*{pi}, in the forward kinematics, where vertical bar t vertical bar Q{sup 2}{approx}s. We obtain the leading twist amplitude in the kinematical region where it factorizes into an antiproton distribution amplitude, a short-distance matrix element related to nucleon form factor and the long-distance dominated transition distribution amplitudes which describe the nucleon to meson transition. We give the Q{sup 2} evolution equation for these transition distribution amplitudes. The scaling of the cross section of this process may be tested at the proposed GSI intense antiproton beam facility FAIR with the PANDA or PAX detectors. We comment on related processes such as {pi}N->N{sup '}{gamma}* and {gamma}*N->N{sup '}{pi} which may be experimentally studied at intense meson beams facilities and at JLab or Hermes, respectively.
Radial distribution function for hard spheres from scaled particle theory, and an improved equation of state
Energy Technology Data Exchange (ETDEWEB)
Reiss, H.; Casberg, R.V.
Previous applications of scaled particle theory have been limited to the calculation of thermodynamic properties of fluids rather than structure. In the present paper, the theory is expanded so that it is capable of yielding the radial distribution function. The method is first illustrated by applying it to one-dimensional fluids of hard rods where, as in other theories, the radial distribution function is obtained exactly. It is then applied to a fluid of hard spheres where a closure condition is necessary. This condition is supported by recent work in scaled particle theory dealing with the thermodynamics of boundary layers. It is used to calculate the radial distribution function around a lambda-cule of varying size, including one of the size of a typical hard sphere solvent molecule. (40 refs.)
Scaling Properties of Chaotic Scattering on hard and pinball like disks
Kyprianou, I; Kyprianou, Iacovos; Alexandrou, Constantia
We study the classically chaotic scattering of particles interacting with various configurations of pinball disks. The system possesses sensitivity not only on the impact parameter, like other systems with hard disks[3], but on the external force produced by the pinballs. This extra sensitivity gives different behaviour of the fractal set in different scales. We present this scaling function which is consistent for many disk configurations, and we talk about the fractal boundaries of the pinball system.
Hamilton, Andrew; The ATLAS collaboration
The ATLAS collaboration has performed studies of a wide range of QCD phenomena, from soft particle to hard photon and jet production. Recent soft-QCD measurements include studies of underlying event, vector meson production and quark confinement effects. Differential measurements of inclusive and multi-jet production provide stringent tests of high-order QCD predictions and provide input for determination of parton density functions. Measurements of isolated inclusive and di-photons cross sections for high p_T photons test various theoretical predictions and constrain parton density functions. In addition the total p-p cross section at 7 TeV, together with the elastic and inelastic contributions, is measured and compared to various models. An overview of these results is given.
QCD measurements at the Tevatron
Selected quantum chromodynamics (QCD) measurements performed at the Fermilab Run II Tevatron ppbar collider running at sqrt{s} = 1.96 TeV by CDF and D0 Collaborations are presented. The inclusive jet, dijet production and three-jet cross section measurements are used to test perturbative QCD calculations, constrain parton distribution function (PDF) determinations, and extract a precise value of the strong coupling constant, alpha_s(m_Z) = 0.1161^{+0.0041}_{-0.0048}. Inclusive photon production cross-section measurements reveal an inability of next-to-leading-order (NLO) perturbative QCD (pQCD) calculations to describe low-energy photons arising directly in the hard scatter. The diphoton production cross-sections check the validity of the NLO pQCD predictions, soft-gluon resummation methods implemented in theoretical calculations, and contributions from the parton-to-photon fragmentation diagrams. Events with W/Z+jets productions are used to measure many kinematic distributions allowing extensive tests and tu...
QCD physics with ATLAS and CMS
Kodolova, Olga
The soft and hard QCD processes are analyzed by the ATLAS and CMS experiments using samples of proton-proton collisions collected by the LHC at sqrt{s}=7 and 8 TeV. Measurements of jet production rates, jet properties, particle multiplicity and particle momentum spectra are presented. The results are compared to predictions of theoretical models at leading- and next-to-leading orders of QCD. The data are used to measure the strong coupling constant and for PDF constraints.
QCD Results from ATLAS and CMS
Leyton, M; The ATLAS collaboration
The ATLAS and CMS collaborations have performed a wide range of studies of QCD phenomena, from soft particle to hard photon and jet production. Recent soft-QCD measurements include studies of the underlying event, double parton interactions and vector meson production. Differential measurements of inclusive and dijet production provide stringent tests of high-order QCD predictions and provide input for the determination of parton density functions. Measurements of isolated, inclusive and di-photon cross sections for high-pT photons test various theoretical predictions and further constrain PDFs. An overview of these results is given.
13. international QCD conference (QCD 06)
Energy Technology Data Exchange (ETDEWEB)
This conference was organized around 5 sessions: 1) quantum chromodynamics (QCD) at colliders, 2) CP-violation, Kaon decays and Chiral symmetry, 3) perturbative QCD, 4) physics of light and heavy hadrons, 5) confinement, thermodynamics QCD and axion searches. This document gathers only the slides of the presentations.
From QCD-based hard-scattering to nonextensive statistical mechanical descriptions of transverse momentum spectra in high-energy p p and p p ¯ collisions
Wong, Cheuk-Yin; Wilk, Grzegorz; Cirto, Leonardo J. L.; Tsallis, Constantino
Transverse spectra of both jets and hadrons obtained in high-energy p p and p p ¯ collisions at central rapidity exhibit power-law behavior of 1 /pTn at high pT . The power index n is 4-5 for jet production and is 6-10 for hadron production. Furthermore, the hadron spectra spanning over 14 orders of magnitude down to the lowest pT region in p p collisions at the LHC can be adequately described by a single nonextensive statistical mechanical distribution that is widely used in other branches of science. This suggests indirectly the possible dominance of the hard-scattering process over essentially the whole pT region at central rapidity in high-energy p p and p p ¯ collisions. We show here direct evidences of such a dominance of the hard-scattering process by investigating the power indices of UA1 and ATLAS jet spectra over an extended pT region and the two-particle correlation data of the STAR and PHENIX collaborations in high-energy p p and p p ¯ collisions at central rapidity. We then study how the showering of the hard-scattering product partons alters the power index of the hadron spectra and leads to a hadron distribution that may be cast into a single-particle nonextensive statistical mechanical distribution. Because of such a connection, the nonextensive statistical mechanical distribution may be considered as a lowest-order approximation of the hard-scattering of partons followed by the subsequent process of parton showering that turns the jets into hadrons, in high-energy p p and p p ¯ collisions.
Lattice QCD. A critical status report
Energy Technology Data Exchange (ETDEWEB)
Jansen, Karl
The substantial progress that has been achieved in lattice QCD in the last years is pointed out. I compare the simulation cost and systematic effects of several lattice QCD formulations and discuss a number of topics such as lattice spacing scaling, applications of chiral perturbation theory, non-perturbative renormalization and finite volume effects. Additionally, the importance of demonstrating universality is emphasized. (orig.)
QCD threshold corrections for gluino pair production at hadron colliders
Energy Technology Data Exchange (ETDEWEB)
Langenfeld, Ulrich [Wuerzburg Univ. (Germany); Moch, Sven-Olaf; Pfoh, Torsten [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)
We present the complete threshold enhanced predictions in QCD for the total cross section of gluino pair production at hadron colliders at next-to-next-to-leading order. Thanks to the computation of the required one-loop hard matching coefficients our results are accurate to the next-to-next-to-leading logarithm. In a brief phenomenological study we provide predictions for the total hadronic cross sections at the LHC and we discuss the uncertainties arising from scale variations and the parton distribution functions.
Power corrections to exclusive processes in QCD
Energy Technology Data Exchange (ETDEWEB)
Mankiewicz, Lech
In practice applicability of twist expansion crucially depends on the magnitude to power corrections to the leading-twist amplitude. I illustrate this point by considering explicit examples of two hard exclusive processes in QCD. In the case of {gamma}{sup *}{gamma} {yields} {pi}{pi} amplitude power corrections are small enough such that it should be possible to describe current experimental data by the leading-twist QCD prediction. The photon helicity-flip amplitude in DVCS on a nucleon receives large kinematical power corrections which screen the leading-twist prediction up to large values of the hard photon virtuality.
Decay constants in soft wall AdS/QCD revisited
Energy Technology Data Exchange (ETDEWEB)
Braga, Nelson R.F., E-mail: firstname.lastname@example.com [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, RJ 21941-972 (Brazil); Diles, Saulo, E-mail: email@example.com [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, RJ 21941-972 (Brazil); Contreras, M.A. Martin, E-mail: firstname.lastname@example.com [High Energy Group, Department of Physics, Universidad de los Andes, Carrera 1, No 18A-10, Bloque Ip, ZIP 111711, Bogotá (Colombia)
Phenomenological AdS/QCD models, like hard wall and soft wall, provide hadronic mass spectra in reasonable consistency with experimental and (or) lattice results. These simple models are inspired in the AdS/CFT correspondence and assume that gauge/gravity duality holds in a scenario where conformal invariance is broken through the introduction of an energy scale. Another important property of hadrons: the decay constant, can also be obtained from these models. However, a consistent formulation of an AdS/QCD model that reproduces the observed behavior of decay constants of vector meson excited states is still lacking. In particular: for radially excited states of heavy vector mesons, the experimental data lead to decay constants that decrease with the radial excitation level. We show here that a modified framework of soft wall AdS/QCD involving an additional dimensionfull parameter, associated with an ultraviolet energy scale, provides decay constants decreasing with radial excitation level. In this version of the soft wall model the two point function of gauge theory operators is calculated at a finite position of the anti-de Sitter space radial coordinate.
New Perspectives for QCD Physics at the LHC
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC /Stanford U. /Southern Denmark U., CP3-Origins
I review a number of topics where conventional wisdom relevant to hadron physics at the LHC has been challenged. For example, the initial-state and final-state interactions of the quarks and gluons entering perturbative QCD hard-scattering subprocesses lead to the breakdown of traditional concepts of factorization and universality for transverse-momentum-dependent observables at leading twist. These soft-gluon rescattering effect produce single-spin asymmetries, the breakdown of the Lam-Tung relation in Drell-Yan reactions, as well as diffractive deep inelastic scattering, The antishadowing of nuclear structure functions is predicted to depend on the flavor quantum numbers of each quark and antiquark. Isolated hadrons can be produced at large transverse momentum directly within a hard higher-twist QCD subprocess, rather than from jet fragmentation, even at the LHC. Such 'direct' processes can explain the observed deviations from pQCD predictions of the power-law fall-off of inclusive hadron cross sections as well as the 'baryon anomaly' seen in high-centrality heavy-ion collisions at RHIC. The intrinsic charm contribution to the proton structure function at high x can explain the large rate for high p{sub T} photon plus charm-jet events observed at the Tevatron and imply a large production rate for charm and bottom jets at high p{sub T} at the LHC, as well as a novel mechanism for Higgs and Z{sup 0} production at high x{sub F}. The light-front wavefunctions derived in AdS/QCD can be used to calculate jet hadronization at the amplitude level. The elimination of the renormalization scale ambiguity for the QCD coupling using the scheme-independent BLM method will increase the sensitivity of searches for new physics at the LHC. The implications of 'in-hadron condensates' for the QCD contribution to the cosmological constant are also discussed.
Two flavor QCD and Confinement
DEFF Research Database (Denmark)
D'Elia, M.; Di Giacomo, A.; Pica, Claudio
We argue that the order of the chiral transition for N_f=2 is a sensitive probe of the QCD vacuum, in particular of the mechanism of color confinement. A strategy is developed to investigate the order of the transition by use of finite size scaling analysis. An in-depth numerical investigation...
Availability of radium isotopes and heavy metals from scales and tailings of Polish hard coal mining.
Leopold, Karsten; Michalik, Boguslaw; Wiegand, Jens
Radium and heavy metal contaminated tailings and scales resulting from Polish hard coal mining were investigated for their mobilisation potential by using leaching methods. The main focus is set on a three-step extraction procedure proposed by BCR (Bureau Communautaire de Référence, now Standards Measurements and Testing Programme) of the European Union, which was used for investigating the availability of radium isotopes. In addition, the results of a Polish extraction procedure for the heavy metals' water solubility are presented for rough comparison. After a special treatment, the BCR-reagents were measured by gamma-spectrometry to define their radium activity concentrations; the heavy metal content in the water soluble fractions was determined by ICP-AES. The samples were collected at two different sites influenced by the discharge of pit water from hard coal mining. The tailings were taken from a former tailing pond, which now is no longer in use, but the settled material is still present. At another abandoned and meanwhile flooded tailing pond, the scales were scraped from the inside of a discharge tube. The results obtained show that there is different leaching behaviour between the radium isotopes. The tailings being characterised by surface adsorbed radium provide up to 25% of the initial (226)Ra content, (228)Ra is altogether leached up to 15%. The scales comprise stable radiobaryte (Ba[Ra]SO(4)) and can be considered as being unable to provide radium isotopes, since no trace of radium dissolution was observed. The leaching behaviour of heavy metals is similar to that of radium. Mn, Ni and Zn are dissolved by water from the tailings; the scales do not provide any.
QCD in hadron-hadron collisions
Energy Technology Data Exchange (ETDEWEB)
Albrow, M.
Quantum Chromodynamics provides a good description of many aspects of high energy hadron-hadron collisions, and this will be described, along with some aspects that are not yet understood in QCD. Topics include high E{sub T} jet production, direct photon, W, Z and heavy flavor production, rapidity gaps and hard diffraction.
Modeling the thermodynamics of QCD
Energy Technology Data Exchange (ETDEWEB)
Hell, Thomas
Strongly interacting (QCD) matter is expected to exhibit a multifaceted phase structure: a hadron gas at low temperatures, a quark-gluon plasma at very high temperatures, nuclear matter in the low-temperature and high-density region, color superconductors at asymptotically high densities. Most of the conjectured phases cannot yet be scrutinized by experiments. Much of the present picture - particularly concerning the intermediate temperature and density area of the phase diagram of QCD matter - is based on model calculations. Further insights come from Lattice-QCD computations. The present thesis elaborates a nonlocal covariant extension of the Nambu and Jona-Lasinio (NJL) model with built-in constraints from the running coupling of QCD at high-momentum and instanton physics at low-momentum scales. We present this model for two and three quark flavors (in the latter case paying particular attention to the axial anomaly). At finite temperatures and densities, gluon dynamics is incorporated through a gluonic background field, expressed in terms of the Polyakov loop (P). The thermodynamics of this nonlocal PNJL model accounts for both chiral and deconfinement transitions. We obtain results in mean-field approximation and beyond, including additional pionic and kaonic contributions to the chiral condensate, the pressure and other thermodynamic quantities. Finally, the nonlocal PNJL model is applied to the finite-density region of the QCD phase diagram; for three quark flavors we investigate, in particular, the dependence of the critical point appearing in the models on the axial anomaly. The thesis closes with a derivation of the nonlocal PNJL model from first principles of QCD. (orig.)
Heavy Quarks, QCD, and Effective Field Theory
Energy Technology Data Exchange (ETDEWEB)
Thomas Mehen
The research supported by this OJI award is in the area of heavy quark and quarkonium production, especially the application Soft-Collinear E ective Theory (SCET) to the hadronic production of quarkonia. SCET is an e ffective theory which allows one to derive factorization theorems and perform all order resummations for QCD processes. Factorization theorems allow one to separate the various scales entering a QCD process, and in particular, separate perturbative scales from nonperturbative scales. The perturbative physics can then be calculated using QCD perturbation theory. Universal functions with precise fi eld theoretic de nitions describe the nonperturbative physics. In addition, higher order perturbative QCD corrections that are enhanced by large logarithms can be resummed using the renormalization group equations of SCET. The applies SCET to the physics of heavy quarks, heavy quarkonium, and similar particles.
Two-scale model for the effect of physical aging in elastomers filled with hard nanoparticles
Semkiv, Mykhailo; Anderson, Patrick D.; Hütter, Markus
A two-scale model is developed, and solved numerically, to describe the mechanical behavior of elastomers filled with hard nanoparticles. Of particular interest is the slow recovery of the elastic modulus after large-amplitude oscillatory deformation. To account for this effect, the physical aging of the glassy bridges between the filler particles is captured with two thermal degrees of freedom for the matrix material, namely a kinetic and a configurational one. Formulating the two-scale model enriched with aging in a nonequilibrium thermodynamics context, first results in a constitutive relation for the Cauchy stress tensor. Second, the dynamics of physical aging is described, which eventually results in the slow recovery of the elastic modulus with waiting time. The proposed model is investigated numerically under large amplitude oscillatory shear deformation. Of particular interest in this respect is the coupling of the micro-scale dynamics with the physical aging on the macroscopic scale. This coupling is examined in detail, both in an approximate way using a Gaussian approximation, as well as numerically, under specific conditions. It turns out that the CONNFFESSIT approach (Laso and Öttinger 1993 [46]) can not be employed for the numerical solution of the model under arbitrary loading conditions because of the novel structure of the two-level coupling term. While a procedure for solving the model numerically for the case of strong applied deformation is presented in this paper, other solution methodologies need to be sought for the cases of weak and no applied deformation.
Tetraquarks in holographic QCD
Gutsche, Thomas; Lyubovitskij, Valery E.; Schmidt, Ivan
Using a soft-wall AdS/QCD approach we derive the Schrödinger-type equation of motion for the tetraquark wave function, which is dual to the dimension-4 AdS bulk profile. The latter coincides with the number of constituents in the leading Fock state of the tetraquark. The obtained equation of motion is solved analytically, providing predictions for both the tetraquark wave function and its mass. A low mass limit for possible tetraquark states is given by M ≥2 κ =1 GeV , where κ =0.5 GeV is the typical value of the scale parameter in soft-wall AdS/QCD. We confirm results of the COMPASS Collaboration recently reported on the discovery of the a1(1414 ) state, interpreted as a tetraquark state composed of light quarks and having JP C=1++. Our prediction for the mass of this state, Ma1=√{2 } GeV ≃1.414 GeV , is in good agreement with the COMPASS result Ma1=1.41 4-0.013+0.015 GeV . Next we included finite quark mass effects, which are essential for the tetraquark states involving heavy quarks.
Large scale gas injection test (Lasgit) performed at the Aespoe Hard Rock Laboratory. Summary report 2008
Energy Technology Data Exchange (ETDEWEB)
Cuss, R.J.; Harrington, J.F.; Noy, D.J. (British Geological Survey (United Kingdom))
This report describes the set-up, operation and observations from the first 1,385 days (3.8 years) of the large scale gas injection test (Lasgit) experiment conducted at the Aespoe Hard Rock Laboratory. During this time the bentonite buffer has been artificially hydrated and has given new insight into the evolution of the buffer. After 2 years (849 days) of artificial hydration a canister filter was identified to perform a series of hydraulic and gas tests, a period that lasted 268 days. The results from the gas test showed that the full-scale bentonite buffer behaved in a similar way to previous laboratory experiments. This confirms the up-scaling of laboratory observations with the addition of considerable information on the stress responses throughout the deposition hole. During the gas testing stage, the buffer was continued to artificially hydrate. Hydraulic results, from controlled and uncontrolled events, show that the buffer continues to mature and has yet to reach full maturation. Lasgit has yielded high quality data relating to the hydration of the bentonite and the evolution in hydrogeological properties adjacent to the deposition hole. The initial hydraulic and gas injection tests confirm the correct working of all control and data acquisition systems. Lasgit has been in successful operation for in excess of 1,385 days
Aespoe Hard Rock Laboratory. Evaluation of scaling records for TASA access tunnel
Energy Technology Data Exchange (ETDEWEB)
Ittner, Henrik (Chalmers Univ. of Technology, Goeteborg (Sweden))
This report presents the result of a project accomplished during the summer 2009. It introduces a method to estimate the magnitude, mass distribution and cause of scaled blocks by tunnel mapping and evaluation of scaling data records. These issues are important for understanding the impact of the excavation method on the surrounding rock mass during excavation of the planned underground repository for spent nuclear fuel. The project includes mapping of the 3120 m drill and blast excavated part of the TASA access tunnel in the Aespoe Hard Rock Laboratory (HRL). In addition it includes development of a method for evaluation of the collected material together with scaling data records from the Site Characterization Database (SICADA). An interview has also been held with Erik Gabrielsson, who has been in charge of tunnel maintenance at Aespoe for many years. The mapping focused on to identify size and cause of areas with significant overbreaks in the tunnel roof. By distributing documented scaled volume in a tunnel section on several mapped overbreak areas in the same section it is possible to reconstruct the size of scaled blocks. The observed overbreak areas have been categorized in five different area types, depending on the cause of scaling: two geologically induced, one blast induced, one induced from a combination of geology and blasting and one unable to place in any category. For the calculated mass distribution the number of observations is declining with increasing block mass. 11% of the total blocks exceeding 400 Kg and 75% of the scaled blocks weights under 200 Kg. Most of the blocks are however lighter with 34% weighting 50 Kg or less. There is a relation between the mapped area type and the size distribution among the mapped overbreak areas. For example the areas caused by the end of blasting rounds are more frequently appearing then the other types but most of them are small in relation to the others The impression achieved from the tunnel mapping is
Continuous Advances in QCD 2008
Peloso, Marco M.
1. High-order calculations in QCD and in general gauge theories. NLO evolution of color dipoles / I. Balitsky. Recent perturbative results on heavy quark decays / J. H. Piclum, M. Dowling, A. Pak. Leading and non-leading singularities in gauge theory hard scattering / G. Sterman. The space-cone gauge, Lorentz invariance and on-shell recursion for one-loop Yang-Mills amplitudes / D. Vaman, Y.-P. Yao -- 2. Heavy flavor physics. Exotic cc¯ mesons / E. Braaten. Search for new physics in B[symbol]-mixing / A. J. Lenz. Implications of D[symbol]-D[symbol] mixing for new physics / A. A. Petrov. Precise determinations of the charm quark mass / M. Steinhauser -- 3. Quark-gluon dynamics at high density and/or high temperature. Crystalline condensate in the chiral Gross-Neveu model / G. V. Dunne, G. Basar. The strong coupling constant at low and high energies / J. H. Kühn. Quarkyonic matter and the phase diagram of QCD / L. McLerran. Statistical QCD with non-positive measure / J. C. Osborn, K. Splittorff, J. J. M. Verbaarschot. From equilibrium to transport properties of strongly correlated fermi liquids / T. Schäfer. Lessons from random matrix theory for QCD at finite density / K. Splittorff, J. J. M. Verbaarschot -- 4. Methods and models of holographic correspondence. Soft-wall dynamics in AdS/QCD / B. Batell. Holographic QCD / N. Evans, E. Threlfall. QCD glueball sum rules and vacuum topology / H. Forkel. The pion form factor in AdS/QCD / H. J. Kwee, R. F. Lebed. The fast life of holographic mesons / R. C. Myers, A. Sinha. Properties of Baryons from D-branes and instantons / S. Sugimoto. The master space of N = 1 quiver gauge theories: counting BPS operators / A. Zaffaroni. Topological field congurations. Skyrmions in theories with massless adjoint quarks / R. Auzzi. Domain walls, localization and confinement: what binds strings inside walls / S. Bolognesi. Static interactions of non-abelian vortices / M. Eto. Vortices which do not abelianize dynamically: semi
QCD corrections to B→π form factors from light-cone sum rules
Directory of Open Access Journals (Sweden)
Yu-Ming Wang
Full Text Available We compute perturbative corrections to B→π form factors from QCD light-cone sum rules with B-meson distribution amplitudes. Applying the method of regions we demonstrate factorization of the vacuum-to-B-meson correlation function defined with an interpolating current for pion, at one-loop level, explicitly in the heavy quark limit. The short-distance functions in the factorization formulae of the correlation function involves both hard and hard-collinear scales; and these functions can be further factorized into hard coefficients by integrating out the hard fluctuations and jet functions encoding the hard-collinear information. Resummation of large logarithms in the short-distance functions is then achieved via the standard renormalization-group approach. We further show that structures of the factorization formulae for fBπ+(q2 and fBπ0(q2 at large hadronic recoil from QCD light-cone sum rules match that derived in QCD factorization. In particular, we perform an exploratory phenomenological analysis of B→π form factors, paying attention to various sources of perturbative and systematic uncertainties, and extract |Vub|=(3.05−0.38+0.54|th.±0.09|exp.×10−3 with the inverse moment of the B-meson distribution amplitude ϕB+(ω determined by reproducing fBπ+(q2=0 obtained from the light-cone sum rules with π distribution amplitudes. Furthermore, we present the invariant-mass distributions of the lepton pair for B→πℓνℓ (ℓ=μ,τ in the whole kinematic region. Finally, we discuss non-valence Fock state contributions to the B→π form factors fBπ+(q2 and fBπ0(q2 in brief.
Energy Technology Data Exchange (ETDEWEB)
Norniella, Olga; /Barcelona, IFAE
Recent QCD measurements from the CDF collaboration at the Tevatron are presented, together with future prospects as the luminosity increases. The measured inclusive jet cross section is compared to pQCD NLO predictions. Precise measurements on jet shapes and hadronic energy flows are compared to different phenomenological models that describe gluon emissions and the underlying event in hadron-hadron interactions.
QCD collinear factorization, its extensions and the partonic distributions
Szymanowski, Lech
I review the basics of the collinear factorization theorem applied primarily to deep inelastic scattering (DIS) involving forward parton distributions (PDFs) and the extensions of this theorem for exclusive processes probing non-forward parton distributions (GPDs), the generalized distribution amplitudes (GDAs) and the transition distribution amplitudes (TDAs). These QCD factorization theorem is an important tool in the description of hard processes in QCD. Whenever valid, it permits to repre...
Recent QCD results from ATLAS at the LHC
Keoshkerian, H; The ATLAS collaboration
The ATLAS collaboration has performed studies of a wide range of QCD phenomena, from soft particle to hard photon and jet production. Recent soft-QCD measurements include studies of underlying event, vector meson production. Differential measurements of inclusive and dijet production provide stringent tests of high-order QCD predictions and provide input for determination of parton density functions. Measurements of isolated inclusive and di-photons cross sections for high p_T photons test various theoretical predictions and constrain parton density functions. An overview of these results is given.
The QCD/SM working group: Summary report
Energy Technology Data Exchange (ETDEWEB)
W. Giele et al.
Quantum Chromo-Dynamics (QCD), and more generally the physics of the Standard Model (SM), enter in many ways in high energy processes at TeV Colliders, and especially in hadron colliders (the Tevatron at Fermilab and the forthcoming LHC at CERN), First of all, at hadron colliders, QCD controls the parton luminosity, which rules the production rates of any particle or system with large invariant mass and/or large transverse momentum. Accurate predictions for any signal of possible ''New Physics'' sought at hadron colliders, as well as the corresponding backgrounds, require an improvement in the control of uncertainties on the determination of PDF and of the propagation of these uncertainties in the predictions. Furthermore, to fully exploit these new types of PDF with uncertainties, uniform tools (computer interfaces, standardization of the PDF evolution codes used by the various groups fitting PDF's) need to be proposed and developed. The dynamics of colour also affects, both in normalization and shape, various observables of the signals of any possible ''New Physics'' sought at the TeV scale, such as, e.g. the production rate, or the distributions in transverse momentum of the Higgs boson. Last, but not least, QCD governs many backgrounds to the searches for this ''New Physics''. Large and important QCD corrections may come from extra hard parton emission (and the corresponding virtual corrections), involving multi-leg and/or multi-loop amplitudes. This requires complex higher order calculations, and new methods have to be designed to compute the required multi-legs and/or multi-loop corrections in a tractable form. In the case of semi-inclusive observables, logarithmically enhanced contributions coming from multiple soft and collinear gluon emission require sophisticated QCD resummation techniques. Resummation is a catch-all name for efforts to extend the predictive power of QCD by summing the large
Charm production and QCD analysis at HERA and LHC
Energy Technology Data Exchange (ETDEWEB)
Zenaiev, Oleksandr
In this thesis the study of charm production in ep and pp collisions is presented. The heavy-quark masses provide a hard scale, allowing the application of perturbative QCD. A measurement of D{sup +}-meson production in deep inelastic scattering with the ZEUS detector at HERA is presented. The analysis was performed using a data sample with an integrated luminosity of 354 pb{sup -1}. Differential cross sections were measured as a function of virtuality Q{sup 2}, inelasticity y, transverse momentum and pseudorapidity of the D{sup +} mesons. Lifetime information was used to reduce the combinatorial background significantly. Next-to-leading-order QCD predictions in the fixed-flavour-number scheme were compared to the data. This measurement was combined with other H1 and ZEUS measurements of charm production. The combination was performed at inclusive level for the reduced charm cross sections, which were obtained from the measured visible cross sections, extrapolated to the full phase space using the shape of the theoretical predictions in the fixed-flavour-number scheme. The combination method accounts for the correlations of the systematic uncertainties among the different datasets, thus allowing cross calibration of different measurements. The combined charm data were compared to QCD predictions in various heavy-flavour schemes and used together with the inclusive production data at HERA as input for QCD analyses to determine the charm running mass in the MS renormalisation scheme and the optimal values of the charm-quark mass parameters in other heavy-flavour schemes. An additional combination of the H1 and ZEUS D{sup *+} visible cross sections was performed to provide the combined cross sections without theory-related uncertainties from the extrapolation procedure. This combination also provides differential cross sections as a function of the D{sup *+} kinematic variables. Next-to-leading-order QCD predictions in the fixed-flavour-number scheme were compared to
Effective field theory approach to parton-hadron conversion in high energy QCD processes
Kinder-Geiger, Klaus
A QCD based effective action is constructed to describe the dynamics of confinement and symmetry breaking in the process of parton-hadron conversion. The deconfined quark and gluon degrees of freedom of the perturbative QCD vacuum are coupled to color singlet collective fields representing the non-perturbative vacuum with broken scale and chiral symmetry. The effective action recovers QCD with its scale and chiral symmetry properties at short space-time distances, but yields at large distances (r > 1 fm) to the formation of symmetry breaking gluon and quark condensates. The approach is applied to the evolution of a fragmenting q\\bar q pair with its generated gluon distribution, starting from a large hard scale Q^2. The modification of the gluon distribution arising from the coupling to the non-perturbative collective field results eventually in a complete condensation of gluons. Color flux tube configurations of the gluons in between the q\\bar q pair are obtained as solutions of the equations of motion. With ...
Hard spectator interactions in B {yields} {pi}{pi} at order {alpha}{sup 2}{sub s}
Energy Technology Data Exchange (ETDEWEB)
Pilipp, V.
In the present thesis I discuss the hard spectator interaction amplitude in B {yields} {pi}{pi} at NLO i.e. at O({alpha}{sup 2}{sub s}). This special part of the amplitude, whose LO starts at O({alpha}{sub s}), is defined in the framework of QCD factorization. QCD factorization allows to separate the short- and the long-distance physics in leading power in an expansion in {lambda}{sub QCD}/m{sub b}, where the short-distance physics can be calculated in a perturbative expansion in {alpha}{sub s}. Compared to other parts of the amplitude hard spectator interactions are formally enhanced by the hard collinear scale {radical}({lambda}{sub QCD}m{sub b}), which occurs next to the mb-scale and leads to an enhancement of {alpha}{sub s}. From a technical point of view the main challenges of this calculation are due to the fact that we have to deal with Feynman integrals that come with up to five external legs and with three independent ratios of scales. These Feynman integrals have to be expanded in powers of {delta}{sub QCD}/m{sub b}. I discuss integration by parts identities to reduce the number of master integrals and differential equations techniques to get their power expansions. A concrete implementation of integration by parts identities in a computer algebra system is given in the appendix. Finally I discuss numerical issues like scale dependence of the amplitudes and branching ratios. It turns out that the NLO contributions of the hard spectator interactions are important but small enough for perturbation theory to be valid. (orig.)
Parton Scattering at Small-x and Scaling Violation
Kim, V T; Vary, J P; Kim, Victor T.; Pivovarov, Grigorii B.
Scaling violation of inclusive jet production at small-$x$ in hadron scattering with increasing total collision energy is discussed. Perturbative QCD based on the factorisation theorem for hard processes and GLAPD evolution equations predicts a minimum for scaled cross-section ratio that depends on jet rapidity. Studies of such a scaling violation can reveal a vivid indication of new dynamical effects in the high-energy limit of QCD. The BFKL effects, which seem to be seen in recent L3 data at CERN LEP2, should give different results from GLAPD predictions.
Dynamical holographic QCD model
Directory of Open Access Journals (Sweden)
Li Danning
Full Text Available We develop a dynamical holographic QCD model, which resembles the renormalization group from ultraviolet (UV to infrared (IR. The dynamical holographic model is constructed in the graviton-dilaton-scalar framework with the dilaton background field Φ and scalar field X responsible for the gluodynamics and chiral dynamics, respectively. We summarize the results on hadron spectra, QCD phase transition and transport properties including the jet quenching parameter and the shear/bulk viscosity in the framework of the dynamical holographic QCD model.
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC; de Teramond, Guy F.; /Costa Rica U. /SLAC
The AdS/CFT correspondence between string theory in AdS space and conformal .eld theories in physical spacetime leads to an analytic, semi-classical model for strongly-coupled QCD which has scale invariance and dimensional counting at short distances and color confinement at large distances. Although QCD is not conformally invariant, one can nevertheless use the mathematical representation of the conformal group in five-dimensional anti-de Sitter space to construct a first approximation to the theory. The AdS/CFT correspondence also provides insights into the inherently non-perturbative aspects of QCD, such as the orbital and radial spectra of hadrons and the form of hadronic wavefunctions. In particular, we show that there is an exact correspondence between the fifth-dimensional coordinate of AdS space z and a specific impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions, the fundamental entities which encode hadron properties and allow the computation of decay constants, form factors, and other exclusive scattering amplitudes. New relativistic lightfront equations in ordinary space-time are found which reproduce the results obtained using the 5-dimensional theory. The effective light-front equations possess remarkable algebraic structures and integrability properties. Since they are complete and orthonormal, the AdS/CFT model wavefunctions can also be used as a basis for the diagonalization of the full light-front QCD Hamiltonian, thus systematically improving the AdS/CFT approximation.
Gravitational waves generated from the cosmological QCD phase transition within AdS/QCD
Directory of Open Access Journals (Sweden)
M. Ahmadvand
Full Text Available We study the gravitational waves produced by the collision of the bubbles as a probe for the cosmological first order QCD phase transition, considering heavy static quarks. Using AdS/QCD and the correspondence between a first order Hawking–Page phase transition and confinement–deconfinement phase transition, we find the spectrum and the strain amplitude of the gravitational wave within the hard and soft wall models. We postulate the duration of the phase transition corresponds to the evaporation time of the black hole in the five dimensional dual gravity space, and thereby obtain a bound on the string length in the space and correspondingly on the duration of the QCD phase transition. We also show that IPTA and SKA detectors will be able to detect these gravitational waves, which can be an evidence for the first order deconfinement transition.
Charm Production and QCD Analysis at HERA and LHC
Zenaiev, Oleksandr; Foster, Brian; McNulty, Ronan
In this thesis the study of charm production in ep and pp collisions is presented. The heavy- quark masses provide a hard scale, allowing the application of perturbative QCD. A measurement of D + -meson production in deep inelastic scattering with the ZEUS detector at HERA is presented. The analysis was performed using a data sample with an integrated luminosity of 354 pb-1. Di erential cross sections were measured as a function of virtuality Q 2 , inelasticity y , transverse momentum and pseudorapidity of the D + mesons. Lifetime infor- mation was used to reduce the combinatorial background significantly. Next-to-leading-order QCD predictions in the fixed-flavour-number scheme were compared to the data. This measurement was combined with other H1 and ZEUS measurements of charm produc- tion. The combination was performed at inclusive level for the reduced charm cross sections, which were obtained from the measured visible cross sections, extrapolated to the full phase space using the shape of the theoretical ...
Sykora, Tomas; The ATLAS collaboration
Recent results of soft QCD measurements performed by the ATLAS collaboration are reported. The measurements include total, elastic and inelastic cross sections, inclusive spectra, underlying event and particle correlations in p-p and p-Pb collisions.
Energy Technology Data Exchange (ETDEWEB)
Lutz, Matthias F. M.; Lange, Jens Sören; Pennington, Michael; Bettoni, Diego; Brambilla, Nora; Crede, Volker; Eidelman, Simon; Gillitzer, Albrecht; Gradl, Wolfgang; Lang, Christian B.; Metag, Volker; Nakano, Takashi; Nieves, Juan; Neubert, Sebastian; Oka, Makoto; Olsen, Stephen L.; Pappagallo, Marco; Paul, Stephan; Pelizäus, Marc; Pilloni, Alessandro; Prencipe, Elisabetta; Ritman, Jim; Ryan, Sinead; Thoma, Ulrike; Uwer, Ulrich; Weise, Wolfram
We report on the EMMI Rapid Reaction Task Force meeting 'Resonances in QCD', which took place at GSI October 12-14, 2015 (Fig.~1). A group of 26 people met to discuss the physics of resonances in QCD. The aim of the meeting was defined by the following three key questions; what is needed to understand the physics of resonances in QCD?; where does QCD lead us to expect resonances with exotic quantum numbers?; and what experimental efforts are required to arrive at a coherent picture? For light mesons and baryons only those with up, down and strange quark content were considered. For heavy-light and heavy-heavy meson systems, those with charm quarks were the focus.This document summarizes the discussions by the participants, which in turn led to the coherent conclusions we present here.
Energy Technology Data Exchange (ETDEWEB)
Skands, Peter Z.; /Fermilab
Recent developments in QCD phenomenology have spurred on several improved approaches to Monte Carlo event generation, relative to the post-LEP state of the art. In this brief review, the emphasis is placed on approaches for (1) consistently merging fixed-order matrix element calculations with parton shower descriptions of QCD radiation, (2) improving the parton shower algorithms themselves, and (3) improving the description of the underlying event in hadron collisions.
Parametric form of QCD travelling waves
Peschanski, R.
We derive parametric travelling-wave solutions of non-linear QCD equations. They describe the evolution towards saturation in the geometric scaling region. The method, based on an expansion in the inverse of the wave velocity, leads to a solvable hierarchy of differential equations. A universal parametric form of travelling waves emerges from the first two orders of the expansion.
Working group report: Quantum chromodynamics (QCD) and ...
Indian Academy of Sciences (India)
Quantum chromodynamics; perturbative; non-perturbative; quark gluon plasma. PACS No. 12.38.-t. 1. Introduction. Quantum chromodynamics (QCD), the theory of strong interaction physics has been well established both theoretically .... are removed by the redefinition of parton densities at some arbitrary factorization scale.
Mechanical design of multiple zone plates precision alignment apparatus for hard X-ray focusing in twenty-nanometer scale
Shu, Deming; Liu, Jie; Gleber, Sophie C.; Vila-Comamala, Joan; Lai, Barry; Maser, Jorg M.; Roehrig, Christian; Wojcik, Michael J.; Vogt, Franz Stefan
An enhanced mechanical design of multiple zone plates precision alignment apparatus for hard x-ray focusing in a twenty-nanometer scale is provided. The precision alignment apparatus includes a zone plate alignment base frame; a plurality of zone plates; and a plurality of zone plate holders, each said zone plate holder for mounting and aligning a respective zone plate for hard x-ray focusing. At least one respective positioning stage drives and positions each respective zone plate holder. Each respective positioning stage is mounted on the zone plate alignment base frame. A respective linkage component connects each respective positioning stage and the respective zone plate holder. The zone plate alignment base frame, each zone plate holder and each linkage component is formed of a selected material for providing thermal expansion stability and positioning stability for the precision alignment apparatus.
Precision QCD measurements in DIS at HERA
Britzger, Daniel
New and recent results on QCD measurements from the H1 and ZEUS experiments at the HERA ep collider are reviewed. The final results on the combined deep-inelastic neutral and charged current cross-sections are presented and their role in the extractions of parton distribution functions (PDFs) is studied. The PDF fits give insight into the compatibility of QCD evolution and heavy flavor schemes with the data as a function of kinematic variables such as the scale Q2. Measurements of jet production cross-sections in ep collisions provide direct proves of QCD and extractions of the strong coupling constants are performed. Charm and beauty cross-section measurements are used for the determination of the heavy quark masses. Their role in PDF fits is investigated. In the regime of diffractive DIS and photoproduction, dijet and prompt photon production cross-sections provide insights into the process of factorization and the nature of the diffractive exchange.
Testing QCD with Hypothetical Tau Leptons
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.
We construct new tests of perturbative QCD by considering a hypothetical {tau} lepton of arbitrary mass, which decays hadronically through the electromagnetic current. We can explicitly compute its hadronic width ratio directly as an integral over the e{sup +}e{sup -} annihilation cross section ratio, R{sub e{sup +}e{sup -}}. Furthermore, we can design a set of commensurate scale relations and perturbative QCD tests by varying the weight function away from the form associated with the V-A decay of the physical {tau}. This method allows the wide range of the R{sub e{sup +}e{sup -}} data to be used as a probe of perturbative QCD.
Inclusive Hard Diffraction at HERA
Proskuryakov, Alexander
Recent data from the H1 and ZEUS experiments on hard inclusive diffraction are discussed. Results of QCD analyses of the diffractive deep-inelastic scattering processes are reported. Predictions based on the extracted parton densities are compared to diffractive dijet measurements.
Energy Technology Data Exchange (ETDEWEB)
Roessner, Simon
Quantum Chromodynamics (QCD) is the theory of the strong interaction within the Standard Model of elementary particles. Today's research in this area dedicates substantial resources to numeric solutions of the QCD field equations and experimental programs exploring the phases of QCD. This thesis proceeds along a complementary line - that of modelling QCD, with the aim of identifying its dominant degrees of freedom. This is possible by minimally coupling effective potentials for the Polyakov loop to Nambu-Jona-Lasinio models using temporal background fields to model chiral symmetry breaking respecting colour confinement. The fermion sign problem resulting from the minimal coupling is addressed in this work establishing a novel, systematically ordered approach. The modifications to the approximative order parameter of colour confinement, the Polyakov loop, are in direct connection with the fermion sign problem. Furthermore an effective coupling of quark densities of different flavours is induced. This mechanism, most likely also present in QCD, produces finite contributions to flavour off diagonal susceptibilities. Susceptibilities are amongst the most promising physical quantities for the experimental exploration of the phase transition at high temperatures and densities. (orig.)
QCD Structure of Nuclear Interactions
Energy Technology Data Exchange (ETDEWEB)
Granados, Carlos [Florida Intl Univ., Miami, FL (United States)
This dissertation investigated selected processes involving baryons and nuclei in hard scattering reactions. Through these processes, this work explored the constituent structure of baryons and the mechanisms through which the interactions between these constituents ultimately control the selected reactions. First, hard nucleon-nucleon elastic scattering was studied considering the quark exchange (QE) between the nucleons to be the dominant mechanism of interaction in the constituent picture. It was found that an angular asymmetry exhibited by proton-neutron (pn) elastic scattering data is explained within this framework if a quark-diquark picture dominates the nucleon's structure instead of a more traditional SU(6) model. The latter yields an asymmetry around 90 deg center of mass scattering with a sign opposite to what is experimentally observed. The second process is the hard breakup by a photon of a nucleon-nucleon system in light nuclei. Proton-proton (pp) and pn breakup in 3He, and double Δ-isobars production in deuteron breakup were analyzed in the hard rescattering model (HRM), which in conjunction with the QE mechanism provides a QCD description of the reaction. Cross sections for both channels in 3He photodisintegration were computed without the need of a fitting parameter. The results presented here for pp breakup show excellent agreement with recent experimental data. In double Δ-isobars production in deuteron breakup, HRM angular distributions for the two double Δ channels were compared to the pn channel and to each other. An important prediction from this study is that the Δ++ Δ- channel consistently dominates Δ+Δ0, which is in contrast with models that unlike the HRM consider a double Δ system in the initial state of the interaction. For such models both channels should have the same strength.
Transport at ''NLO'' in hot QCD
CERN. Geneva
The study of QCD kinetics is driven by a vast array of the experimental measurements of transport at the LHC, ranging from heavy quark energy loss, jet suppression, and hydrodynamics. I first review the fundamental elements of QCD kinetic theory, i.e. plasma screening, 2to2 scattering, and medium modified collinear bremsstrahlung. Then I will summarize recent progress in calculating these elements and their interplay at "NLO" -- "NLO" refers to an order $\\sqrt{\\alpha_s}$ correction to the plasma processes arising from the statistical fluctuations of soft gluons. These "NLO" calculations suggest a computational strategy where the influence of the Debye sector on the real time dynamics of the hard lightlike modes can be incorporated into a few medium coefficients (such as the drag coefficient and $\\hat{q}$), which can be simulated with a Euclidean 3D dimensionally reduced theory.
QCD Aspects of Exclusive B Decays
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.
Exclusive B decays can be factorized as convolutions of hard scattering amplitudes involving the weak interaction with universal hadron distribution amplitudes, thus providing a new QCD-based phenomenology. In addition, semi-leptonic decay amplitudes can be computed exactly in terms of the diagonal and off-diagonal {Delta} = 2 overlap of hadronic light-cone wavefunctions. I review these formalisms and the essential QCD ingredients. A canonical form of the light-cone wavefunctions, valid at low values of the transverse momenta, is presented. The existence of intrinsic charm Fock states in the B meson wavefunction can enhance the production of final states of B-decay with three charmed quarks, such as B {yields} J/{psi}D, as well as lead to the breakdown of the CKM hierarchy.
Comparing and counting logs in direct and effective methods of QCD resummation
Energy Technology Data Exchange (ETDEWEB)
Almeida, Leandro G. [Laboratoire de Physique Théorique, Université Paris-Sud 11 and CNRS,91405 Orsay Cedex (France); Institut de Biologie de l'École Normale Supérieure (IBENS),Inserm 1024-CNRS 8197, 46 rue d'Ulm, 75005 Paris (France); Ellis, Stephen D. [Department of Physics, University of Washington,Seattle, WA 98195 (United States); Lee, Christopher [Theoretical Division, MS B283, Los Alamos National Laboratory,Los Alamos, NM 87544 (United States); Sterman, George [C.N. Yang Institute for Theoretical Physics, Stony Brook University,Stony Brook, NY 11794 (United States); Sung, Ilmo [Department of Applied Physics, New York University,Brooklyn, NY 11201 (United States); Queens College, City University of New York,Flushing, NY 11367 (United States); Walsh, Jonathan R. [Lawrence Berkeley National Laboratory, University of California,Berkeley, CA 94720 (United States); Berkeley Center for Theoretical Physics, University of California,Berkeley, CA 94720 (United States)
We compare methods to resum logarithms in event shape distributions as they have been used in perturbative QCD directly and in effective field theory. We demonstrate that they are equivalent. In showing this equivalence, we are able to put standard soft-collinear effective theory (SCET) formulae for cross sections in momentum space into a novel form more directly comparable with standard QCD formulae, and endow the QCD formulae with dependence on separated hard, jet, and soft scales, providing potential ways to improve estimates of theoretical uncertainty. We show how to compute cross sections in momentum space to keep them as accurate as the corresponding expressions in Laplace space. In particular, we point out that that care is required in truncating differential distributions at N{sup k}LL accuracy to ensure they match the accuracy of the corresponding cumulant or Laplace transform. We explain how to avoid such mismatches at N{sup k}LL accuracy, and observe why they can also be avoided by working to N{sup k}LL{sup ′} accuracy.
Scattering vector mesons in D4-D8 holographic QCD
Energy Technology Data Exchange (ETDEWEB)
Boschi-Filho, Henrique; Braga, Nelson; Ballon Bayona, C.A.; Torres, Marcus A.C. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil)
Full text. Sakai and Sugimoto authored one of the most successful string top-down models in describing real QCD, the D4-D8 brane model of holographic QCD. This model succeeds in exhibiting chiral symmetry breaking and confinement.A drawback of this model is that all massive hadrons have their masses set by the Kaluza-Klein compactification scale and we would have to work at energy scales below 1 GeV in order to describe a four dimensional physics. Still, they were able to find pion form factors and pion in agreement with experiment at scale of 1 GeV and above. They also calculate pion quadratic square radius in check with experiment, from a formula that depends on the entire Kaluza-Klein tower of excited pion states. Their model also realizes vector meson dominance (VMD) in electromagnetic interaction as proposed by Sakurai in the sixties. 5D gauge fields from flavor symmetry provides a zoo of mesons (scalar, pseudo-scalar, vector and pseudo-vector) and instanton configurations of such fields are interpreted as baryon fields. Inspired by the results of pion form factors and pion quadratic radius predicted in close agreement with experiment, we further calculate vector and axial vector mesons {psi}(z) wave functions, form factors, we discuss about its Q{sup -2} power behavior at large virtuosity (Q{sup 2}), and we check necessary relations between coupling constants and masses (superconvergence) that grants such power behavior of form factors. We compare our results with what is found in bottom-up hard wall and soft wall models and discuss the problems of the D4-D8 model. (author)
Lombardo, M P
I review recent results on QCD at high temperature on a lattice. Steady progress with staggered fermions and Wilson type fermions allow a quantitative description of hot QCD whose accuracy in many cases parallels that of zero temperature studies. Simulations with chiral quarks are coming of age, and togheter with theoretical developments trigger interesting developments in the analysis of the critical region. Issues related with the universality class of the chiral transition and the fate of the axial symmetry are discussed in the light of new numerical and analytical results. Transport coefficients and analysis of bottomonium spectra compare well with results of heavy ion collisions at RHIC and LHC. Model field theories, lattice simulations and high temperature systematic expansions help building a coherent picture of the high temperature phase of QCD. The (strongly coupled) Quark Gluon Plasma is heavily investigated, and asserts its role as an inspiring theoretical laboratory.
These are the proceedings of the QCD Evolution 2015 Workshop which was held 26–30 May, 2015 at Jefferson Lab, Newport News, Virginia, USA. The workshop is a continuation of a series of workshops held during four consecutive years 2011, 2012, 2013 at Jefferson Lab, and in 2014 in Santa Fe, NM. With the rapid developments in our understanding of the evolution of parton distributions including low-x, TMDs, GPDs, higher-twist correlation functions, and the associated progress in perturbative QCD, lattice QCD and effective field theory techniques we look forward with great enthusiasm to the 2015 meeting. A special attention was also paid to participation of experimentalists as the topics discussed are of immediate importance for the JLab 12 experimental program and a future Electron Ion Collider.
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Shindler, A. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed. (orig.)
Damgaard, P H; Sollacher, R
A gauge-symmetric approach to effective Lagrangians is described with special emphasis on derivations of effective low-energy Lagrangians from QCD. The examples we discuss are based on exact rewritings of cut-off QCD in terms of new collective degrees of freedom. These cut-off Lagrangians are thus ``effective'' in the sense that they explicitly contain some of the physical long-distance degrees of freedom from the outset.(Talk presented by P.H. Damgaard at the workshop on ``Quantum Field Theoretical Methods in High Energy Physics'', Kyffhauser, Germany, Sept. 1993. To appear in those proceedings).
Narison, Stéphan
The aim of the book is to give an introduction to the method of QCD Spectral Sum Rules and to review its developments. After some general introductory remarks, Chiral Symmetry, the Historical Developments of the Sum Rules and the necessary materials for perturbative QCD including the MS regularization and renormalization schemes are discussed. The book also gives a critical review and some improvements of the wide uses of the QSSR in Hadron Physics and QSSR beyond the Standard Hadron Phenomenology. The author has participated actively in this field since 1978 just before the expanding success
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Brodsky, Stanley J.; Deshpande, Abhay L.; Gao, Haiyan; McKeown, Robert D.; Meyer, Curtis A.; Meziani, Zein-Eddine; Milner, Richard G.; Qiu, Jianwei; Richards, David G.; Roberts, Craig D.
This White Paper presents the recommendations and scientific conclusions from the Town Meeting on QCD and Hadronic Physics that took place in the period 13-15 September 2014 at Temple University as part of the NSAC 2014 Long Range Planning process. The meeting was held in coordination with the Town Meeting on Phases of QCD and included a full day of joint plenary sessions of the two meetings. The goals of the meeting were to report and highlight progress in hadron physics in the seven years since the 2007 Long Range Plan (LRP07), and present a vision for the future by identifying the key questions and plausible paths to solutions which should define the next decade. The introductory summary details the recommendations and their supporting rationales, as determined at the Town Meeting on QCD and Hadron Physics, and the endorsements that were voted upon. The larger document is organized as follows. Section 2 highlights major progress since the 2007 LRP. It is followed, in Section 3, by a brief overview of the physics program planned for the immediate future. Finally, Section 4 provides an overview of the physics motivations and goals associated with the next QCD frontier: the Electron-Ion-Collider.
Mirror QCD and Cosmological Constant
Directory of Open Access Journals (Sweden)
Roman Pasechnik
Full Text Available An analog of Quantum Chromo Dynamics (QCD sector known as mirror QCD (mQCD can affect the cosmological evolution due to a non-trivial contribution to the Cosmological Constant analogous to that induced by the ground state in non-perturbative QCD. In this work, we explore a plausible hypothesis for trace anomalies cancellation between the usual QCD and mQCD. Such an anomaly cancellation between the two gauge theories, if it exists in Nature, would lead to a suppression or even elimination of their contributions to the Cosmological Constant. The trace anomaly compensation condition and the form of the non-perturbative mQCD coupling constant in the infrared limit have been proposed by analysing a partial non-perturbative solution of the Einstein–Yang-Mills equations of motion.
Shear viscosity and structural scalings in model adhesive hard-sphere gels
Eberle, Aaron P. R.; Martys, Nicos; Porcar, Lionel; Kline, Steven R.; George, William L.; Kim, Jung M.; Butler, Paul D.; Wagner, Norman J.
We present experiments and simulations that show a fundamental scaling for both the rheology and microstructure of flowing gels. Unique flow-SANS measurements demonstrate that the structure orients along both the neutral and compression axis. We quantify the anisotropy using a single parameter, αn, that scales by a dimensionless number, M', that arises from a force balance on a particle. Simulations support the scalings and confirm the results are independent of the shape and range of the potential suggesting a universal for colloidal gels with short-ranged attractions.
Energy Technology Data Exchange (ETDEWEB)
Smith, W.H. [Univ. of Wisconsin, Madison, WI (United States). Physics Dept.
These lectures describe QCD physics studies over the period 1992--1996 from data taken with collisions of 27 GeV electrons and positrons with 820 GeV protons at the HERA collider at DESY by the two general-purpose detectors H1 and ZEUS. The focus of these lectures is on structure functions and jet production in deep inelastic scattering, photoproduction, and diffraction. The topics covered start with a general introduction to HERA and ep scattering. Structure functions are discussed. This includes the parton model, scaling violation, and the extraction of F{sub 2}, which is used to determine the gluon momentum distribution. Both low and high Q{sup 2} regimes are discussed. The low Q{sup 2} transition from perturbative QCD to soft hadronic physics is examined. Jet production in deep inelastic scattering to measure {alpha}{sub s}, and in photoproduction to study resolved and direct photoproduction, is also presented. This is followed by a discussion of diffraction that begins with a general introduction to diffraction in hadronic collisions and its relation to ep collisions, and moves on to deep inelastic scattering, where the structure of diffractive exchange is studied, and in photoproduction, where dijet production provides insights into the structure of the Pomeron. 95 refs., 39 figs.
Next-to-leading-order QCD corrections to e+e- → H + γ
Sang, Wen-Long; Chen, Wen; Feng, Feng; Jia, Yu; Sun, Qing-Feng
The associated production of Higgs boson with a hard photon at lepton collider, i.e., e+e- → Hγ, is known to bear a rather small cross section in Standard Model, and can serve as a sensitive probe for the potential new physics signals. Similar to the loop-induced Higgs decay channels H → γγ , Zγ, the e+e- → Hγ process also starts at one-loop order provided that the tiny electron mass is neglected. In this work, we calculate the next-to-leading-order (NLO) QCD corrections to this associated H + γ production process, which mainly stem from the gluonic dressing to the top quark loop. The QCD corrections are found to be rather modest at lower center-of-mass energy range (√{ s } Higgs factory such as CEPC. Nevertheless, when the energy is boosted to the ILC energy range (√{ s } ≈ 400 GeV), QCD corrections may enhance the leading-order cross section by 20%. In any event, the e+e- → Hγ process has a maximal production rate σmax ≈ 0.08 fb around √{ s } = 250 GeV, thus CEPC turns out to be the best place to look for this rare Higgs production process. In the high energy limit, the effect of NLO QCD corrections become completely negligible, which can be simply attributed to the different asymptotic scaling behaviors of the LO and NLO cross sections, where the former exhibits a milder decrement ∝ 1 / s , but the latter undergoes a much faster decrease ∝ 1 /s2.
Next-to-leading-order QCD corrections to e+eââH+γ
Directory of Open Access Journals (Sweden)
Wen-Long Sang
Full Text Available The associated production of Higgs boson with a hard photon at lepton collider, i.e., e+eââHγ, is known to bear a rather small cross section in Standard Model, and can serve as a sensitive probe for the potential new physics signals. Similar to the loop-induced Higgs decay channels Hâγγ,Zγ, the e+eââHγ process also starts at one-loop order provided that the tiny electron mass is neglected. In this work, we calculate the next-to-leading-order (NLO QCD corrections to this associated H+γ production process, which mainly stem from the gluonic dressing to the top quark loop. The QCD corrections are found to be rather modest at lower center-of-mass energy range (s<300 GeV, thus of negligible impact on Higgs factory such as CEPC. Nevertheless, when the energy is boosted to the ILC energy range (sâ400 GeV, QCD corrections may enhance the leading-order cross section by 20%. In any event, the e+eââHγ process has a maximal production rate Ïmaxâ0.08 fb around s=250 GeV, thus CEPC turns out to be the best place to look for this rare Higgs production process. In the high energy limit, the effect of NLO QCD corrections become completely negligible, which can be simply attributed to the different asymptotic scaling behaviors of the LO and NLO cross sections, where the former exhibits a milder decrement â1/s , but the latter undergoes a much faster decrease â1/s2. Keywords: Standard Model, Higgs boson, QCD corrections
Hard scale abrasive jetting removal system: a solution for Brazilian offshore operations
Energy Technology Data Exchange (ETDEWEB)
Santos, Iuri [Schlumberger, Rio de Janeiro, RJ (Brazil); Quiroga, Marcelo H.; Calmeto, Joao C.; Assis, Carlos A.; Pinto, Salvador L. [PETROBRAS, Rio de Janeiro, RJ (Brazil)
Scale deposition in producing well bores is becoming a serious problem to the oil industry. On situations of injected seawater breakthrough, the problem is especially difficult, since the growth is often Barium or Strontium Sulfate, which are almost completely insoluble. Further growth will decrease the flowing area and hinder the production. Ultimately the scale can restrict the production tubing to such a degree preventing access for tools into lower sections of the well and finally it can bridge over completely. The range of options for scale removal goes from a simple brush run using slick line or basic chemical treatment up to a full rig work over to replace the production string. Very often through tubing treatments using coiled tubing are used due to the savings compared to rig cost. This technology can convey tools for mechanical scale removal and also works as a fluid conduit for chemical treatments. The objective of this paper is to describe the coiled tubing abrasive jetting technology used to successfully clean, for the first time, production tubing in Brazilian offshore operations, heavily affected by Barium Sulfate scale in and its impact on the well economics. (author)
Heavy-Quark Associated Production with One Hard Photon at Hadron Colliders
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Hartanto, Heribertus Bayu [Florida State Univ., Tallahassee, FL (United States)
We present the calculation of heavy-quark associated production with a hard photon at hadron colliders, namely $pp(p\\bar p) → Q\\bar Q +X$γ (for $Q=t,b$), at Next-to-Leading Order (NLO) in Quantum Chromodynamics (QCD). We study the impact of NLO QCD corrections on the total cross section and several differential distributions at both the Tevatron and the Large Hadron Collider (LHC). For $t\\bar t$γ production we observe a sizeable reduction of the renormalization and factorization scale dependence when the NLO QCD corrections are included, while for $b\\bar b$γ production a considerable scale dependence still persists at NLO in QCD. This is consistent with what emerges in similar processes involving $b$ quarks and vector bosons and we explain its origin in detail. For $b\\bar b$γ production we study both the case in which at least one $b$ jet and the case in which at least two $b$ jets are observed. We perform the $b\\bar b$γ calculation using the Four Flavor Number Scheme (4FNS) and compare the case where at least one $b$ jet is observed with the corresponding results from the Five Flavor Number Scheme (5FNS) calculation. Finally we compare our results for $p\\bar p →+b+X$γ with the Tevatron data.
Anomalous couplings in WZ production beyond NLO QCD
Energy Technology Data Exchange (ETDEWEB)
Campanario, Francisco; Roth, Robin; Zeppenfeld, Dieter [Institute for Theoretical Physics, KIT, Karlsruhe (Germany); Sapeta, Sebastian [CERN PH-TH, Geneva (Switzerland)
We study WZ production with anomalous couplings (AC) at anti nNLO QCD using the LoopSim method in combination with the Monte Carlo program VBFNLO. Higher order corrections to WZ production are dominated by additional hard jet radiation. Those contributions are insensitive to AC and should thus be suppressed in analyses. We do this using a dynamical jet veto based on the transverse energy of the QCD and EW final state particles. This removes jet dominated events without introducing problematic logs like a fixed p{sub T} jet veto.
A rapid, small-scale sedimentation method to predict breadmaking quality of hard winter wheat
Breeders and processors are always looking for rapid and accurate methods to evaluate wheat quality. A rapid small-scale hybrid sedimentation method was developed for predicting breadmaking quality of breeders samples by combining the sodium dodecyl-sulfate (SDS) sedimentation method (AACC 56-70) an...
Scales and dermal skeletal histology of an early bony fish Psarolepis romeri and their bearing on the evolution of rhombic scales and hard tissues.
Directory of Open Access Journals (Sweden)
Qingming Qu
Full Text Available Recent discoveries of early bony fishes from the Silurian and earliest Devonian of South China (e.g. Psarolepis, Achoania, Meemannia, Styloichthys and Guiyu have been crucial in understanding the origin and early diversification of the osteichthyans (bony fishes and tetrapods. All these early fishes, except Guiyu, have their dermal skeletal surface punctured by relatively large pore openings. However, among these early fishes little is known about scale morphology and dermal skeletal histology. Here we report new data about the scales and dermal skeletal histology of Psarolepis romeri, a taxon with important implications for studying the phylogeny of early gnathostomes and early osteichthyans. Seven subtypes of rhombic scales with similar histological composition and surface sculpture are referred to Psarolepis romeri. They are generally thick and show a faint antero-dorsal process and a broad peg-and-socket structure. In contrast to previously reported rhombic scales of osteichthyans, these scales bear a neck between crown and base as in acanthodian scales. Histologically, the crown is composed of several generations of odontodes and an irregular canal system connecting cylindrical pore cavities. Younger odontodes are deposited on older ones both superpositionally and areally. The bony tissues forming the keel of the scale are shown to be lamellar bone with plywood-like structure, whereas the other parts of the base are composed of pseudo-lamellar bone with parallel collagen fibers. The unique tissue combination in the keel (i.e., extrinsic Sharpey's fibers orthogonal to the intrinsic orthogonal sets of collagen fibers has rarely been reported in the keel of other rhombic scales. The new data provide insights into the early evolution of rhombic (ganoid and cosmoid scales in osteichthyans, and add to our knowledge of hard tissues of early vertebrates.
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Dudek, Jozef [Old Dominion Univ., Norfolk, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
I describe how hadron-hadron scattering amplitudes are related to the eigenstates of QCD in a finite cubic volume. The discrete spectrum of such eigenstates can be determined from correlation functions computed using lattice QCD, and the corresponding scattering amplitudes extracted. I review results from the Hadron Spectrum Collaboration who have used these finite volume methods to study ππ elastic scattering, including the ρ resonance, as well as coupled-channel πK, ηK scattering. The very recent extension to the case where an external current acts is also presented, considering the reaction πγ* → ππ, from which the unstable ρ → πγ transition form factor is extracted. Ongoing calculations are advertised and the outlook for finite volume approaches is presented.
Energy Technology Data Exchange (ETDEWEB)
Gupta, R.
The goal of the lectures on lattice QCD (LQCD) is to provide an overview of both the technical issues and the progress made so far in obtaining phenomenologically useful numbers. The lectures consist of three parts. The author`s charter is to provide an introduction to LQCD and outline the scope of LQCD calculations. In the second set of lectures, Guido Martinelli will discuss the progress they have made so far in obtaining results, and their impact on Standard Model phenomenology. Finally, Martin Luescher will discuss the topical subjects of chiral symmetry, improved formulation of lattice QCD, and the impact these improvements will have on the quality of results expected from the next generation of simulations.
Gaillard, J M; Gastmans, Raymond; Jacob, Maurice René Michel; Speiser, D; Weyers, J
In an experiment in the CERN Super Proton Synchrotron (SPS) charged hyperon beam, 2400 Omega /sup -/ decays have been collected. The analysis of the Omega /sup -/ sample has given an accurate measurement of the Omega /sup -/ lifetime ( tau ( Omega /sup -/)=(0.822+or-0.028) *10/sup -10/ s) and the first determination of the Omega /sup -/ decay branching ratios. In particular the measured ratio Gamma ( Omega /sup -/ to Xi /sup 0/ pi /sup -/)/ Gamma ( Omega /sup -/ to Xi /sup -/ pi /sup 0/) is 2.94+or-0.35, while a pure Delta I=1/2 amplitude would have given 2.03. A ratio of about 3 between those two decay modes had in fact been predicted by Finjord using the QCD framework. The author discusses briefly what QCD has to say about hyperon decays, then describes the Omega /sup -/ experiment and the analysis results. (8 refs).
Baryon Interactions from Lattice QCD
Aoki, Sinya
We report on new attempt to investigate baryon-baryon interactions in lattice QCD. From the Bethe-Salpeter (BS) wave function, we have successfully extracted the nucleon-nucleon ($NN$) potentials in quenched QCD simulations, which reproduce qualitative features of modern $NN$ potentials. The method has been extended to obtain the tensor potential as well as the central potential and also applied to the hyperon-nucleon ($YN$) interactions, in both quenched and full QCD.
Experimental application of QCD antennas
Energy Technology Data Exchange (ETDEWEB)
Bobrovskyi, Sergei
A serious problem in searches for new physics at the LHC is the rejection of QCD induced multijet events. In this thesis the formalism of QCD antenna variables based on the SPHEL approximation of QCD matrix elements is applied for the rst time on experimentally reconstructed jets in order to discriminate QCD from supersymmetric processes. The new observables provide additional information with respect to traditional event shape variables. Albeit correlated with experimentally measured missing transverse energy, the variables can be used to improve the signal to background ratio. (orig.)
Effective Quark Interactions and QCD-Propagators
Bergerhoff, Bastian; Wetterich, Christof
We compute the momentum dependence of the effective four quark interaction in QCD after integrating out the gluons. Our method is based on a truncation of exact renormalization group equations which should give reasonable results for momenta above the confinement scale. The difference between the four quark interaction and the heavy quark potential can be minimized for an optimal renormalization scheme in Landau gauge. Within the momentum range relevant for quarkonia our results agree with ph...
Lattice QCD with commodity hardware and software
Energy Technology Data Exchange (ETDEWEB)
Holmgren, D.J. [and others
Large scale QCD Monte Carlo calculations have typically been performed on either commercial supercomputers or specially built massively parallel computers such as Fermilab's ACPMAPS. Commodity computer systems offer impressive floating point performance-to-cost ratios which exceed those of commercial supercomputers. As high performance networking components approach commodity pricing, it becomes reasonable to assemble a massively parallel supercomputer from commodity parts. The authors describe the work and progress to date of a collaboration working on this problem.
Scaling laws for the mechanics of loose and cohesive granular materials based on Baxter's sticky hard spheres.
Gaume, Johan; Löwe, Henning; Tan, Shurun; Tsang, Leung
We have conducted discrete element simulations (pfc3d) of very loose, cohesive, granular assemblies with initial configurations which are drawn from Baxter's sticky hard sphere (SHS) ensemble. The SHS model is employed as a promising auxiliary means to independently control the coordination number z_{c} of cohesive contacts and particle volume fraction ϕ of the initial states. We focus on discerning the role of z_{c} and ϕ for the elastic modulus, failure strength, and the plastic consolidation line under quasistatic, uniaxial compression. We find scaling behavior of the modulus and the strength, which both scale with the cohesive contact density ν_{c}=z_{c}ϕ of the initial state according to a power law. In contrast, the behavior of the plastic consolidation curve is shown to be independent of the initial conditions. Our results show the primary control of the initial contact density on the mechanics of cohesive granular materials for small deformations, which can be conveniently, but not exclusively explored within the SHS-based assembling procedure.
Experimental Summary Moriond QCD 2007
Rolandi, Gigi
More than 90 speakers gave a presentation at this years Moriond QCD conference and more than 60 talks reported the experimental status and perspectives on Standard Model, especially QCD, search for new physics, quark spectroscopy and Heavy Ions physics. I summarize what I consider the highlights of these presentations.
Energy Technology Data Exchange (ETDEWEB)
Brodsky, S.
In these lectures, I survey a number of applications of light-front methods to hadron and nuclear physics phenomenology and dynamics, including light-front statistical physics. Light-front Fock-state wavefunctions provide a frame-independent representation of hadrons in terms of their fundamental quark and gluon degrees of freedom. Nonperturbative methods for computing LFWFs in QCD are discussed, including string/gauge duality which predicts the power-law fall-off at high momentum transfer of light-front Fock-state hadronic wavefunctions with an arbitrary number of constituents and orbital angular momentum. The AdS/CFT correspondence has important implications for hadron phenomenology in the conformal limit, including an all-orders derivation of counting rules for exclusive processes. One can also compute the hadronic spectrum of near-conformal QCD assuming a truncated AdS/CFT space. Given the LFWFs, one can compute form factors, heavy hadron decay amplitudes, hadron distribution amplitudes, and the generalized parton distributions underlying deeply virtual Compton scattering. The quantum fluctuations represented by the light-front Fock expansion leads to novel QCD phenomena such as color transparency, intrinsic heavy quark distributions, diffractive dissociation, and hidden-color components of nuclear wavefunctions. A new test of hidden color in deuteron photodisintegration is proposed. The origin of leading-twist phenomena such as the diffractive component of deep inelastic scattering, single-spin asymmetries, nuclear shadowing and antishadowing is also discussed; these phenomena cannot be described by light-front wavefunctions of the target computed in isolation. Part of the anomalous NuTeV results for the weak mixing angle {theta}{sub W} could be due to the non-universality of nuclear antishadowing for charged and neutral currents.
QCD at the Tevatron: Jets and fragmentation
Energy Technology Data Exchange (ETDEWEB)
V. Daniel Elvira
At the Fermilab Tevatron energies, ({radical} s=1800 GeV and {radical} s = 630 GeV), jet production is the dominant process. During the period 1992-1996, the D0 and CDF experiments accumulated almost 100 pb{sup -1} of data and performed the most accurate jet production measurements up to this date. These measurements and the NLO-QCD theoretical predictions calculated during the last decade, have improved our understanding of QCD, our knowledge of the proton structure, and pushed the limit to the scale associated with quark compositeness to 2.4-2.7 TeV. In this paper, we present the most recent published and preliminary measurements on jet production and fragmentation by the D0 and CDF collaborations.
Kenneth Wilson and lattice QCD
Ukawa, Akira
We discuss the physics and computation of lattice QCD, a space-time lattice formulation of quantum chromodynamics, and Kenneth Wilson's seminal role in its development. We start with the fundamental issue of confinement of quarks in the theory of the strong interactions, and discuss how lattice QCD provides a framework for understanding this phenomenon. A conceptual issue with lattice QCD is a conflict of space-time lattice with chiral symmetry of quarks. We discuss how this problem is resolved. Since lattice QCD is a non-linear quantum dynamical system with infinite degrees of freedom, quantities which are analytically calculable are limited. On the other hand, it provides an ideal case of massively parallel numerical computations. We review the long and distinguished history of parallel-architecture supercomputers designed and built for lattice QCD. We discuss algorithmic developments, in particular the difficulties posed by the fermionic nature of quarks, and their resolution. The triad of efforts toward b...
Energy Technology Data Exchange (ETDEWEB)
Ali, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kramer, G. [Hamburg Univ. (Germany). II. Inst. fuer Theoretische Physik
The observation of quark and gluon jets has played a crucial role in establishing Quantum Chromodynamics [QCD] as the theory of the strong interactions within the Standard Model of particle physics. The jets, narrowly collimated bundles of hadrons, reflect configurations of quarks and gluons at short distances. Thus, by analysing energy and angular distributions of the jets experimentally, the properties of the basic constituents of matter and the strong forces acting between them can be explored. In this review we summarise the properties of quark and gluon jets and the impact of their observation on Quantum Chromodynamics, primarily the discovery of the gluons as the carriers of the strong force. Focusing on these basic points, jets in e{sup +}e{sup -} collisions will be in the foreground of the discussion. In addition we will delineate the role of jets as tools for exploring other particle aspects in ep and pp/p anti p collisions - quark and gluon densities in protons, measurements of the QCD coupling, fundamental 2-2 quark/gluon scattering processes, but also the impact of jet decays of top quarks, and W{sup {+-}},Z bosons on the electroweak sector. The presentation to a large extent is formulated in a non-technical language with the intent to recall the significant steps historically and convey the significance of this field also to communities beyond high energy physics. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Soltz, R; Vranas, P; Blumrich, M; Chen, D; Gara, A; Giampap, M; Heidelberger, P; Salapura, V; Sexton, J; Bhanot, G
The theory of the strong nuclear force, Quantum Chromodynamics (QCD), can be numerically simulated from first principles on massively-parallel supercomputers using the method of Lattice Gauge Theory. We describe the special programming requirements of lattice QCD (LQCD) as well as the optimal supercomputer hardware architectures that it suggests. We demonstrate these methods on the BlueGene massively-parallel supercomputer and argue that LQCD and the BlueGene architecture are a natural match. This can be traced to the simple fact that LQCD is a regular lattice discretization of space into lattice sites while the BlueGene supercomputer is a discretization of space into compute nodes, and that both are constrained by requirements of locality. This simple relation is both technologically important and theoretically intriguing. The main result of this paper is the speedup of LQCD using up to 131,072 CPUs on the largest BlueGene/L supercomputer. The speedup is perfect with sustained performance of about 20% of peak. This corresponds to a maximum of 70.5 sustained TFlop/s. At these speeds LQCD and BlueGene are poised to produce the next generation of strong interaction physics theoretical results.
The strong coupling constant of QCD with four flavors
Energy Technology Data Exchange (ETDEWEB)
Tekin, Fatih
In this thesis we study the theory of strong interaction Quantum Chromodynamics on a space-time lattice (lattice QCD) with four flavors of dynamical fermions by numerical simulations. In the early days of lattice QCD, only pure gauge field simulations were accessible to the computational facilities and the effects of quark polarization were neglected. The so-called fermion determinant in the path integral was set to one (quenched approximation). The reason for this approximation was mainly the limitation of computational power because the inclusion of the fermion determinant required an enormous numerical effort. However, for full QCD simulations the virtual quark loops had to be taken into account and the development of new machines and new algorithmic techniques made the so-called dynamical simulations with at least two flavors possible. In recent years, different collaborations studied lattice QCD with dynamical fermions. In our project we study lattice QCD with four degenerated flavors of O(a) improved Wilson quarks in the Schroedinger functional scheme and calculate the energy dependence of the strong coupling constant. For this purpose, we determine the O(a) improvement coefficient c{sub sw} with four flavors and use this result to calculate the step scaling function of QCD with four flavors which describes the scale evolution of the running coupling. Using a recursive finite-size technique, the {lambda} parameter is determined in units of a technical scale L{sub max} which is an unambiguously defined length in the hadronic regime. The coupling {alpha}{sub SF} of QCD in the so-called Schroedinger functional scheme is calculated over a wide range of energies non-perturbatively and compared with 2-loop and 3-loop perturbation theory as well as with the non-perturbative result for only two flavors. (orig.)
Breakdown of QCD factorization theorems for inclusive reactions
Energy Technology Data Exchange (ETDEWEB)
Brodsky, S.J.; Bodwin, G.T.; Lepage, G.P.
Initial state interactions are shown to violate standard factorization for massive lepton pair production and hadron-induced hard-scattering inclusive reactions order-by-order in QCD perturbation theory. Initial and final state interactions lead to a number of new physical phenomena including K/sub 1/ fluctuations, color correlations, anomalous nuclear number dependence of inclusive cross sections, and induced hadron production in the central rapidity region.
Light-cone quantized QCD and novel hadron phenomenology
Energy Technology Data Exchange (ETDEWEB)
Brodsky, S.J.
The authors reviews progress made in solving gauge theories such as collinear quantum chromodynamics using light-cone Hamiltonian methods. He also shows how the light-cone Fock expansion for hadron wavefunctions can be used to compute operator matrix elements such as decay amplitudes, form factors, distribution amplitudes, and structure functions, and how it provides a tool for exploring novel features of QCD. The author also reviews commensurate scale relations, leading-twist identities which relate physical observables to each other, thus eliminating renormalization scale and scheme ambiguities in perturbative QCD predictions.
Industrial scale HP-HT synthesis of hard and wear resistant c-Zr3N4
Dzivenko, Dmytro; Riedel, Ralf; Taniguchi, Takashi; Chauveau, Thierry; Zerr, Andreas
We present a large scale high-pressure high-temperature (HP-HT) synthesis of hard and wear resistant cubic zirconium nitride having Th3P4-type structure,c-Zr3N4. This material, also available as well-adhesive coatings with exceptional wear resistance, represents a compound competitive to diamond and c-BN with respect to machining of low-carbon steels and other ferrous alloys. We obtained c-Zr3N4 powder at pressures as low as 6.5 GPa and temperatures of 1400-1600 °C from nanocrystalline Zr3N4+x precursor using a belt-type apparatus - a static HP-HT device widely employed for the commercial production of diamond and c-BN. The HP products are characterized in details by means of powder X-ray diffraction, Raman spectroscopy, scanning electron microscopy and combustion elemental analysis. In addition to major polycrystalline c-Zr3N4, we unveil the formation of a quaternary compound c-(Zr1-xTax)3 (N1-yOy)4 which indicates the possibility of doping of c-Zr3N4, thus introducing it for practical application as a multifunctional material. Moreover, we consider ways of cementing the c-Zr3N4 powders (similar to cemented tungsten carbides) which would allow economic fabrication of large bodies based on this compound. Supported by the DFG (Bonn, Germany) within SPP 1236 and by the IFR ``Paris Nord Plaine de France''.
International Meeting: Excited QCD 2014
Giacosa, Francesco; Malek, Magdalena; Marinkovic, Marina; Parganlija, Denis
Excited QCD 2014 will take place on the beautiful Bjelasnica mountain located in the vicinity of the Bosnian capital Sarajevo. Bjelasnica was a venue of the XIV Winter Olympic Games and it is situated only 30 kilometers from Sarajevo International Airport. The workshop program will start on February 2 and finish on February 8, 2014, with scientific lectures taking place from February 3 to 7. Workshop participants will be accomodated in Hotel Marsal, only couple of minutes by foot from the Olympic ski slopes. ABOUT THE WORKSHOP This edition is the sixth in a series of workshops that were previously organised in Poland, Slovakia, France and Portugal. Following the succesful meeting in 2013, the Workshop is returning to Sarajevo Olympic mountains in 2014, exactly thirty years after the Games. The workshop covers diverse aspects of QCD: (i) QCD at low energies: excited hadrons, glueballs, multiquarks. (ii) QCD at high temperatures and large densities: heavy-ion collisions, jets, diffraction, hadronisation, quark-...
Pleskot, V; The ATLAS collaboration
The ATLAS collaboration has performed studies of a wide range of QCD phenomena. Recent soft-QCD measurements include studies of underlying event, hadronic event shapes, double parton scattering, diffraction, internal jet structure, jet shapes for heavy quark jets and forward energy flow. Differential measurements of inclusive and dijet production provide stringent tests of higher order QCD predictions and provide input for determination of parton density functions. Inclusive jet multiplicity ratios are sensitive to the strong coupling constant alpha_S. Measurements of the inclusive prompt isolated photon and diphoton cross sections provide a direct probe of short-distance physics. The results are compared to various theoretical models and next-to-leading-order or higher-order QCD calculations.
Kus, V; The ATLAS collaboration
The ATLAS collaboration has performed studies of a wide range of QCD phenomena. Recent soft-QCD measurements include studies of underlying event, hadronic event shapes, double parton scattering, diffraction, internal jet structure, jet shapes for heavy quark jets and forward energy flow. Differential measurements of inclusive and dijet production provide stringent tests of higher order QCD predictions and provide input for determination of parton density functions. Inclusive jet multiplicity ratios are sensitive to the strong coupling constant alpha_S. Measurements of the inclusive prompt isolated photon and diphoton cross sections provide a direct probe of short-distance physics. The results are compared to various theoretical models and next-to-leading-order or higher-order QCD calculations.
Isoscalar meson spectroscopy from lattice QCD
Dudek, Jozef J; Joo, Balint; Peardon, Michael J; Richards, David G; Thomas, Christopher E
We extract to high statistical precision an excited spectrum of single-particle isoscalar mesons using lattice QCD, including states of high spin and, for the first time, light exotic JPC isoscalars. The use of a novel quark field construction has enabled us to overcome the long-standing challenge of efficiently including quark-annihilation contributions. Hidden-flavor mixing angles are extracted and while most states are found to be close to ideally flavor mixed, there are examples of large mixing in the pseudoscalar and axial sectors in line with experiment. The exotic JPC isoscalar states appear at a mass scale comparable to the exotic isovector states.
Precision probes of QCD at high energies
Alioli, Simone; Farina, Marco; Pappadopulo, Duccio; Ruderman, Joshua T.
New physics, that is too heavy to be produced directly, can leave measurable imprints on the tails of kinematic distributions at the LHC. We use energetic QCD processes to perform novel measurements of the Standard Model (SM) Effective Field Theory. We show that the dijet invariant mass spectrum, and the inclusive jet transverse momentum spectrum, are sensitive to a dimension 6 operator that modifies the gluon propagator at high energies. The dominant effect is constructive or destructive interference with SM jet production. We compare differential next-to-leading order predictions from POWHEG to public 7 TeV jet data, including scale, PDF, and experimental uncertainties and their respective correlations. We constrain a New Physics (NP) scale of 3.5 TeV with current data. We project the reach of future 13 and 100 TeV measurements, which we estimate to be sensitive to NP scales of 8 and 60 TeV, respectively. As an application, we apply our bounds to constrain heavy vector octet colorons that couple to the QCD current. We project that effective operators will surpass bump hunts, in terms of coloron mass reach, even for sequential couplings.
Non-perturbative studies of QCD at small quark masses
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Wennekers, J.
We investigate the quenched approximation of lattice QCD with numerical simulations of Ginsparg-Wilson fermions, which are a fermion discretisation with exact chiral symmetry. We compute the renormalisation constant of the scalar density, which allows to extrapolate the chiral condensate to the continuum limit. Furthermore we match lattice results of matrix elements describing hadronic kaon decays to Chiral Perturbation Theory in finite volume and at almost vanishing quark mass. The resulting low-energy constants in the considered SU(4)-flavour symmetric case indicate a substantial contribution of low scale QCD effects to the {delta}I = 1/2 rule. (Orig.)
Directory of Open Access Journals (Sweden)
Andrianov Alexander
Full Text Available The chiral imbalance (ChI is given by a difference between the numbers of RH and LH quarks which may occur in the fireball after heavy ion collision. To characterize it adiabatically a quark chiral (axial chemical potential must be introduced taking into account emergence of a ChI in such a phase. In this report the phenomenology of formation of Local spatial Parity Breaking (LPB in the hot and dense baryon matter is discussed and its simulation within a number of QCD-inspired models is outlined. The appearance of new states in the spectra of scalar, pseudoscalar and vector particles in such a matter is elucidated. In particular, from the effective vector meson theory in the presence of Chern-Simons interaction it is demonstrated that the spectrum of massive vector mesons splits into three polarization components with different effective masses. The asymmetry in production of longitudinally and transversely polarized states of ρ and ω mesons for various values of the dilepton invariant mass can serve as a characteristic indication of the LPB in PHENIX, STAR and ALICE experiments.
Hadroquarkonium from lattice QCD
Alberti, Maurizio; Bali, Gunnar S.; Collins, Sara; Knechtli, Francesco; Moir, Graham; Söldner, Wolfgang
The hadroquarkonium picture [S. Dubynskiy and M. B. Voloshin, Phys. Lett. B 666, 344 (2008), 10.1016/j.physletb.2008.07.086] provides one possible interpretation for the pentaquark candidates with hidden charm, recently reported by the LHCb Collaboration, as well as for some of the charmoniumlike "X , Y , Z " states. In this picture, a heavy quarkonium core resides within a light hadron giving rise to four- or five-quark/antiquark bound states. We test this scenario in the heavy quark limit by investigating the modification of the potential between a static quark-antiquark pair induced by the presence of a hadron. Our lattice QCD simulations are performed on a Coordinated Lattice Simulations (CLS) ensemble with Nf=2 +1 flavors of nonperturbatively improved Wilson quarks at a pion mass of about 223 MeV and a lattice spacing of about a =0.0854 fm . We study the static potential in the presence of a variety of light mesons as well as of octet and decuplet baryons. In all these cases, the resulting configurations are favored energetically. The associated binding energies between the quarkonium in the heavy quark limit and the light hadron are found to be smaller than a few MeV, similar in strength to deuterium binding. It needs to be seen if the small attraction survives in the infinite volume limit and supports bound states or resonances.
Andrianov, Alexander; Andrianov, Vladimir; Espriu, Domenec
The chiral imbalance (ChI) is given by a difference between the numbers of RH and LH quarks which may occur in the fireball after heavy ion collision. To characterize it adiabatically a quark chiral (axial) chemical potential must be introduced taking into account emergence of a ChI in such a phase. In this report the phenomenology of formation of Local spatial Parity Breaking (LPB) in the hot and dense baryon matter is discussed and its simulation within a number of QCD-inspired models is outlined. The appearance of new states in the spectra of scalar, pseudoscalar and vector particles in such a matter is elucidated. In particular, from the effective vector meson theory in the presence of Chern-Simons interaction it is demonstrated that the spectrum of massive vector mesons splits into three polarization components with different effective masses. The asymmetry in production of longitudinally and transversely polarized states of ρ and ω mesons for various values of the dilepton invariant mass can serve as a characteristic indication of the LPB in PHENIX, STAR and ALICE experiments.
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Brandt, Bastian B. [Institute for Theoretical Physics, Goethe-University of Frankfurt,60438 Frankfurt (Germany); Institute for Theoretical Physics, University of Regensburg,93040 Regensburg (Germany); Lohmayer, Robert; Wettig, Tilo [Institute for Theoretical Physics, University of Regensburg,93040 Regensburg (Germany)
We explore an alternative discretization of continuum SU(N{sub c}) Yang-Mills theory on a Euclidean spacetime lattice, originally introduced by Budzcies and Zirnbauer. In this discretization the self-interactions of the gauge field are induced by a path integral over N{sub b} auxiliary boson fields, which are coupled linearly to the gauge field. The main progress compared to earlier approaches is that N{sub b} can be as small as N{sub c}. In the present paper we (i) extend the proof that the continuum limit of the new discretization reproduces Yang-Mills theory in two dimensions from gauge group U(N{sub c}) to SU(N{sub c}), (ii) derive refined bounds on N{sub b} for non-integer values, and (iii) perform a perturbative calculation to match the bare parameter of the induced gauge theory to the standard lattice coupling. In follow-up papers we will present numerical evidence in support of the conjecture that the induced gauge theory reproduces Yang-Mills theory also in three and four dimensions, and explore the possibility to integrate out the gauge fields to arrive at a dual formulation of lattice QCD.
Quark–gluon plasma phenomenology from anisotropic lattice QCD
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Skullerud, Jon-Ivar; Kelly, Aoife [Department of Mathematical Physics, Maynooth University, Maynooth, Co Kildare (Ireland); Aarts, Gert; Allton, Chris; Amato, Alessandro; Evans, P. Wynne M.; Hands, Simon [Department of Physics, Swansea University, Swansea SA2 8PP, Wales (United Kingdom); Burnier, Yannis [Institut de Théorie des Phénomènes Physiques, Ecole Polytechnique Fédérale de Lausanne, CH–1015 Lausanne (Switzerland); Giudice, Pietro [Institut für Theoretische Physik, Universität Münster, D–48149 Münster (Germany); Harris, Tim; Ryan, Sinéad M. [School of Mathematics, Trinity College, Dublin 2 (Ireland); Kim, Seyong [Department of Physics, Sejong University, Seoul 143-747 (Korea, Republic of); Lombardo, Maria Paola [INFN–Laboratori Nazionali di Frascati, I–00044 Frascati (RM) (Italy); Oktay, Mehmet B. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States); Rothkopf, Alexander [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, D–69120 Heidelberg (Germany)
The FASTSUM collaboration has been carrying out simulations of N{sub f} = 2 + 1 QCD at nonzero temperature in the fixed-scale approach using anisotropic lattices. Here we present the status of these studies, including recent results for electrical conductivity and charge diffusion, and heavy quarkonium (charm and beauty) physics.
Decay constants in soft wall AdS/QCD revisited
Directory of Open Access Journals (Sweden)
Nelson R.F. Braga
We show here that a modified framework of soft wall AdS/QCD involving an additional dimensionfull parameter, associated with an ultraviolet energy scale, provides decay constants decreasing with radial excitation level. In this version of the soft wall model the two point function of gauge theory operators is calculated at a finite position of the anti-de Sitter space radial coordinate.
The running coupling of QCD with four flavors
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Tekin, Fatih; Wolff, Ulli [Berlin Univ. (Germany). Inst. fuer Physik; Sommer, Rainer [DESY, Zeuthen (Germany). NIC
We have calculated the step scaling function and the running coupling of QCD in the Schroedinger functional scheme with four flavors of O(a) improved Wilson quarks. Comparisons of our non-perturbative results with 2-loop and 3-loop perturbation theory as well as with non-perturbative data for only two flavors are made. (orig.)
Higher twist, heavy quark, and coherent phenomena in QCD
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Brodsky, S.J.
Scaling violations in QCD arise in two basic ways: (1) logarithmic corrections, associated with the variation of the running coupling constant and the radiative corrections which produce structure- and fragmentation-function evolution; and (2) power-law corrections, due to finite mass effects, multiparticle scattering processes, coherent wavefunction effects, and other non-perturbative phenomena. Aspects are briefly discussed.
Quality Metrics of Digitally Derived Imagery and Their Relation to Interpreter Performance. III. Subjective Scaling of Hard-Copy Digital Imagery.
tCnrv11nwo ort ieee,.. oad. It nereesrr and identitv , b , lock- etvr - - Hard-copy digital Imagery was studied witht respect to subjective imare quality...40 20. The eff.e- ct of Blur x Noise on NATO scale value, Scene 10 .......... ................... 4U 21. The relationship between stress...8217 LUJ S33- 2 3 4 5 6 7 8 9 IC SCENE Fi JlJr,2 5: The ef f ( ct o f Scene on NATO scale vilu- 131 jr x Noise . The Blur x Noise interaction is shown in
NLO QCD corrections to $W Z J J$ production at the LHC
Campanario, Francisco; Ninh, Le Duc; Zeppenfeld, Dieter
We present a summary of the first calculation of NLO QCD corrections to WZjj production with leptonic decays at the LHC. Our results show that the next-to-leading order corrections reduce significantly the scale uncertainties.
QCD Jets and particle correlations in heavy-ion collisions
Nguyen, Matthew
Measurements of jets and particle correlations in nucleus-nucleus collisions are intended to probe QCD interactions in the high temperature phase, where matter is understood to behave as a quark-gluon plasma. Two probes are reviewed: jets which are used to study the energy loss of hard-scattered partons in this medium and particle correlations which are used to understand collective effects of the bulk matter. Whereas collisions of lighter systems, namely proton-ion and proton-proton, initially served primarily as control experiments, certain (but not all) effects first observed in nucleus-nucleus collisions have proven to be pervasive in these systems. Comparative measurements in these three systems have broadened our understanding of many-body QCD phenomena, and raised new questions. This talk reviewed these recent developments.
AdS/QCD and Light Front Holography: A New Approximation to QCD
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Brodsky, Stanley J.; de Teramond, Guy
The combination of Anti-de Sitter space (AdS) methods with light-front holography leads to a semi-classical first approximation to the spectrum and wavefunctions of meson and baryon light-quark bound states. Starting from the bound-state Hamiltonian equation of motion in QCD, we derive relativistic light-front wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. These equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-J modes in anti-de Sitter (AdS) space. Its eigenvalues give the hadronic spectrum, and its eigenmodes represent the probability distribution of the hadronic constituents at a given scale. Applications to the light meson and baryon spectra are presented. The predicted meson spectrum has a string-theory Regge form M{sup 2} = 4{kappa}{sup 2}(n+L+S/2); i.e., the square of the eigenmass is linear in both L and n, where n counts the number of nodes of the wavefunction in the radial variable {zeta}. The space-like pion form factor is also well reproduced. One thus obtains a remarkable connection between the description of hadronic modes in AdS space and the Hamiltonian formulation of QCD in physical space-time quantized on the light-front at fixed light-front time {tau}. The model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms.
Infrared behavior of real-time quark dispersion relations in hot QCD
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Bouakaz, K.; Abada, A. [Departement de Physique, Laboratoire de Physique des Particules et de Physique Statistique, Ecole Normale Superieure, BP 92 Vieux-Kouba, Algiers (Algeria)
We determine the analytic contributions to the complex self energy of slow-moving quarks in the context of hard-thermal-loop summed perturbation of massless quantum chromodynamics (QCD) at high temperature. The calculation is done using the real time formalism.
Simulating QCD at finite density
de Forcrand, Philippe
In this review, I recall the nature and the inevitability of the "sign problem" which plagues attempts to simulate lattice QCD at finite baryon density. I present the main approaches used to circumvent the sign problem at small chemical potential. I sketch how one can predict analytically the severity of the sign problem, as well as the numerically accessible range of baryon densities. I review progress towards the determination of the pseudo-critical temperature T_c(mu), and towards the identification of a possible QCD critical point. Some promising advances with non-standard approaches are reviewed.
Archeology and evolution of QCD
De Rújula, A.
These are excerpts from the closing talk at the "XIIth Conference on Quark Confinement and the Hadron Spectrum", which took place last Summer in Thessaloniki --an excellent place to enjoy an interest in archeology. A more complete personal view of the early days of QCD and the rest of the Standard Model is given in [1]. Here I discuss a few of the points which --to my judgement-- illustrate well the QCD evolution (in time), both from a scientific and a sociological point of view.
Archeology and evolution of QCD
De Rújula, A.
These are excerpts from the closing talk at the "XIIth Conference on Quark Confinement and the Hadron Spectrum", which took place last Summer in Thessaloniki -an excellent place to enjoy an interest in archeology. A more complete personal view of the early days of QCD and the rest of the Standard Model is given in [1]. Here I discuss a few of the points which -to my judgement- illustrate well the QCD evolution (in time), both from a scientific and a sociological point of view.
Hadron Interactions from lattice QCD
Directory of Open Access Journals (Sweden)
Aoki Sinya
Full Text Available We review our strategy to study hadron interactions from lattice QCD using newly proposed potential method. We first explain our strategy in the case of nuclear potentials and its application to nuclear physics. We then discuss the origin of the repulsive core, by adding strange quarks to the system. We also explore a possibility for H-dibaryon to exist in flavor SU(3 limit of lattice QCD. We conclude the paper with an application of our strategy to investigate the maximum mass of neutron stars.
Neutron star structure from QCD
Fraga, Eduardo S; Vuorinen, Aleksi
In this review article, we argue that our current understanding of the thermodynamic properties of cold QCD matter, originating from first principles calculations at high and low densities, can be used to efficiently constrain the macroscopic properties of neutron stars. In particular, we demonstrate that combining state-of-the-art results from Chiral Effective Theory and perturbative QCD with the current bounds on neutron star masses, the Equation of State of neutron star matter can be obtained to an accuracy better than 30% at all densities.
Archeology and evolution of QCD
Directory of Open Access Journals (Sweden)
De Rújula A.
Full Text Available These are excerpts from the closing talk at the "XIIth Conference on Quark Confinement and the Hadron Spectrum", which took place last Summer in Thessaloniki –an excellent place to enjoy an interest in archeology. A more complete personal view of the early days of QCD and the rest of the Standard Model is given in [1]. Here I discuss a few of the points which –to my judgement– illustrate well the QCD evolution (in time, both from a scientific and a sociological point of view.
Hadron scattering, resonances, and QCD
Energy Technology Data Exchange (ETDEWEB)
Briceno, Raul [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
The non-perturbative nature of quantum chromodynamics (QCD) has historically left a gap in our understanding of the connection between the fundamental theory of the strong interactions and the rich structure of experimentally observed phenomena. For the simplest properties of stable hadrons, this is now circumvented with the use of lattice QCD (LQCD). In this talk I discuss a path towards a rigorous determination of few-hadron observables from LQCD. I illustrate the power of the methodology by presenting recently determined scattering amplitudes in the light-meson sector and their resonance content.
QCD inequalities for hadron interactions.
Detmold, William
We derive generalizations of the Weingarten-Witten QCD mass inequalities for particular multihadron systems. For systems of any number of identical pseudoscalar mesons of maximal isospin, these inequalities prove that near threshold interactions between the constituent mesons must be repulsive and that no bound states can form in these channels. Similar constraints in less symmetric systems are also extracted. These results are compatible with experimental results (where known) and recent lattice QCD calculations, and also lead to a more stringent bound on the nucleon mass than previously derived, m_{N}≥3/2m_{π}.
Novel QCD Effects from Initial and Final State Interactions
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Brodsky, Stanley J.
Initial-state and final-state interactions which are conventionally neglected in the parton model, have a profound effect in QCD hard-scattering reactions. The effects, which arise from gluon exchange between the active and spectator quarks, cause leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, and the breakdown of the Lam-Tung relation in Drell-Yan reactions. Diffractive deep inelastic scattering also leads to nuclear shadowing and non-universal antishadowing of nuclear structure functions through multiple scattering reactions in the nuclear target. Factorization-breaking effects are particularly important for hard hadron interactions since both initial-state and final-state interactions appear. Related factorization breaking effects can also appear in exclusive electroproduction reactions and in deeply virtual Compton scattering. None of the effects of initial-state and final-state interactions are incorporated in the light-front wavefunctions of the target hadron computed in isolation.
Oderda, G
In this dissertation we study the resummation of soft gluon corrections in several different jet cross sections. We start by resumming threshold logarithms in dijet differential cross sections from hadron-hadron scattering, at large momentum transfer. We find that the resummed formulas depend on the method used to define the jets in the final state. We then show how to extend the resummation of threshold corrections to single-particle and single-jet inclusive cross sections, which represent a wider class of problems with phenomenological interest. We confirm the structure of our resummed expressions by comparison with explicit one-loop calculations for the two cases of direct photon and heavy quark production. We show that the evolution of color flow in the underlying hard scattering is controlled by soft anomalous dimension matrices, specific to each hard- scattering reaction. We exhibit the one-loop color-mixing matrices for the full list of 2 → 2 reactions involving light quarks and gluons. A very...
Hard processes in hadronic interactions
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Satz, H. [CERN, Geneva (Switzerland)]|[Universitat Bielefeld (Germany); Wang, X.N. [Lawrence Berkeley Lab., CA (United States)
Quantum chromodynamics is today accepted as the fundamental theory of strong interactions, even though most hadronic collisions lead to final states for which quantitative QCD predictions are still lacking. It therefore seems worthwhile to take stock of where we stand today and to what extent the presently available data on hard processes in hadronic collisions can be accounted for in terms of QCD. This is one reason for this work. The second reason - and in fact its original trigger - is the search for the quark-gluon plasma in high energy nuclear collisions. The hard processes to be considered here are the production of prompt photons, Drell-Yan dileptons, open charm, quarkonium states, and hard jets. For each of these, we discuss the present theoretical understanding, compare the resulting predictions to available data, and then show what behaviour it leads to at RHIC and LHC energies. All of these processes have the structure mentioned above: they contain a hard partonic interaction, calculable perturbatively, but also the non-perturbative parton distribution within a hadron. These parton distributions, however, can be studied theoretically in terms of counting rule arguments, and they can be checked independently by measurements of the parton structure functions in deep inelastic lepton-hadron scattering. The present volume is the work of Hard Probe Collaboration, a group of theorists who are interested in the problem and were willing to dedicate a considerable amount of their time and work on it. The necessary preparation, planning and coordination of the project were carried out in two workshops of two weeks` duration each, in February 1994 at CERn in Geneva andin July 1994 at LBL in Berkeley.
Threefold Complementary Approach to Holographic QCD
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Brodsky, Stanley J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); de Teramond, Guy F. [Univ. of Costa Rica, San Jose (Costa Rica); Dosch, Hans Gunter [Inst. for Theoretical Physics, Heidelberg (Germany)
A complementary approach, derived from (a) higher-dimensional anti-de Sitter (AdS) space, (b) light-front quantization and (c) the invariance properties of the full conformal group in one dimension leads to a nonperturbative relativistic light-front wave equation which incorporates essential spectroscopic and dynamical features of hadron physics. The fundamental conformal symmetry of the classical QCD Lagrangian in the limit of massless quarks is encoded in the resulting effective theory. The mass scale for confinement emerges from the isomorphism between the conformal group andSO(2,1). This scale appears in the light-front Hamiltonian by mapping to the evolution operator in the formalism of de Alfaro, Fubini and Furlan, which retains the conformal invariance of the action. Remarkably, the specific form of the confinement interaction and the corresponding modification of AdS space are uniquely determined in this procedure.
QCD Phase Transitions, Volume 15
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Schaefer, T.; Shuryak, E.
The title of the workshop, ''The QCD Phase Transitions'', in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discussion of the underlying non-perturbative mechanisms which manifest themselves as all those phases. Before we go to specifics, let us emphasize one important aspect of the present status of non-perturbative Quantum Field Theory in general. It remains true that its studies do not get attention proportional to the intellectual challenge they deserve, and that the theorists working on it remain very fragmented. The efforts to create Theory of Everything including Quantum Gravity have attracted the lion share of attention and young talent. Nevertheless, in the last few years there was also a tremendous progress and even some shift of attention toward emphasis on the unity of non-perturbative phenomena. For example, we have seen some efforts to connect the lessons from recent progress in Supersymmetric theories with that in QCD, as derived from phenomenology and lattice. Another example is Maldacena conjecture and related development, which connect three things together, string theory, super-gravity and the (N=4) supersymmetric gauge theory. Although the progress mentioned is remarkable by itself, if we would listen to each other more we may have chance to strengthen the field and reach better understanding of the spectacular non-perturbative physics.
QCD calculations for jet substructure
Dasgupta, Mrinal; Salam, Gavin P.
We present results on novel analytic calculations to describe invariant mass distributions of QCD jets with three substructure algorithms: trimming, pruning and the mass-drop taggers. These results not only lead to considerable insight into the behaviour of these tools, but also show how they can be improved. As an example, we discuss the remarkable properties of the modified mass-drop tagger.
Energy Technology Data Exchange (ETDEWEB)
Jackson, A.D. [Niels Bohr Inst., Copenhagen (Denmark)
Chiral random matrix theory has recently been shown to provide a tool useful for both modeling chiral symmetry restoration in QCD and for providing analytic descriptions of the microscopic spectral content of lattice gauge simulations. The basic ideas of chiral random matrix theory and some recent results are discussed. (orig.) 24 refs.
Tasevsky, Marek; The ATLAS collaboration
Results from recent soft QCD measurements by LHC experiments ALICE, ATLAS, CMS, LHCb, LHCf and TOTEM are reported. The measurements include total, elastic and inelastic cross sections, inclusive and identified particle spectra, underlying event and hadronic chains. Results from particle correlations in all three collision systems, namely pp, pPb and PbPb, exhibit unexpected similarities.
Tasevsky, Marek; The ATLAS collaboration
Results of recent soft QCD measurements by LHC experiments ALICE, ATLAS, CMS, LHCb, LHCf and TOTEM are reported. The measurements include total, elastic and inelastic cross sections, inclusive and identified particle spectra, underlying event and particle correlations in all three collision systems: pp, pPb and PbPb.
Seven topics in perturbative QCD
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Buras, A.J.
The following topics of perturbative QCD are discussed: (1) deep inelastic scattering; (2) higher order corrections to e/sup +/e/sup -/ annihilation, to photon structure functions and to quarkonia decays; (3) higher order corrections to fragmentation functions and to various semi-inclusive processes; (4) higher twist contributions; (5) exclusive processes; (6) transverse momentum effects; (7) jet and photon physics.
Hybrid Charmonium from Lattice QCD
Luo, X Q
We review our recent results on the JPC = 0¡¡ exotic hybrid charmonium mass and JPC = 0¡+, 1¡¡ and 1++ nonexotic hybrid charmonium spectrum from anisotropic improved lattice QCD and discuss the relevance to the recent discovery of the Y(4260) state and future experimental search for other states.
Meson Resonances from Lattice QCD
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Edwards, Robert G. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
There has been recent, significant, advances in the determination of the meson spectrum of QCD. Current efforts have focused on the development and application of finite-volume formalisms that allow for the determination of scattering amplitudes as well as resonance behavior in coupled channel systems. I will review some of these recent developments, and demonstrate the viability of the method in meson systems.
Confinement and the supercritical Pomeron in QCD
White, Alan R.
Deep-inelastic diffractive scaling violations have provided fundamental insight into the QCD Pomeron, suggesting a single-gluon inner structure rather than that of a perturbative two-gluon bound state. This paper derives a high-energy, transverse momentum cutoff, confining solution of QCD. The Pomeron, in a first approximation, is a single Reggeized gluon plus a ``wee-parton'' component that compensates for the color and particle properties of the gluon. This solution corresponds to a supercritical phase of Reggeon field theory. Beginning with the multi-Regge behavior of massive quark and gluon amplitudes, Reggeon unitarity is used to derive a Reggeon diagram description of a wide class of multi-Regge amplitudes, including those describing the formation and scattering of bound-state Regge poles. When quark and gluon masses are taken to zero, a logarithmic divergence is produced by helicity-flip Reggeon interactions containing the infrared quark triangle anomaly. With the gauge symmetry partially broken, this divergence selects the bound states and amplitudes of a confining theory. Both the Pomeron and hadrons have an anomalous color-parity wee-parton component. For the Pomeron the wee-parton component determines that it carries negative color charge parity and that the leading singularity is an isolated Regge pole.
Renormalization and applications of baryon distribution amplitudes QCD
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Rohrwild, Juergen Holger
Higher-twist effects are relevant for precision calculations of hard exclusive reactions. Furthermore, they reveal fine details of the hadron structure. In this work we construct an operator basis for arbitrary twist respecting the conformal symmetry of QCD (which is realized on 1-loop level). Using this basis the 1-loop renormalization kernels of twist 4 are constructed for baryon operators. The full spectrum of anomalous dimensions and the multiplicatively renormalizable operators is obtained. As an application of these results the radiative N{sup *}(1535) decay is discussed. Employing light-cone sum rule, the transition form factors can be directly related to the N{sup *} distribution amplitudes. (orig.)
Renormalization and applications of baryon distribution amplitudes in QCD
Energy Technology Data Exchange (ETDEWEB)
Rohrwild, Juergen Holger
Higher-twist effects are relevant for precision calculations of hard exclusive reactions. Furthermore, they reveal fine details of the hadron structure. In this work we construct an operator basis for arbitrary twist respecting the conformal symmetry of QCD (which is realized on 1-loop level). Using this basis the 1-loop renormalization kernels of twist 4 are constructed for baryon operators. The full spectrum of anomalous dimensions and the multiplicatively renormalizable operators is obtained. As an application of these results the radiative N{sup *}(1535) decay is discussed. Employing light-cone sum rule, the transition form factors can be directly related to the N* distribution amplitudes. (orig.)
Azimuthal decorrelations between QCD jets at all orders
Energy Technology Data Exchange (ETDEWEB)
Banfi, A. [Universita degli studi di Milano-Bicocca and INFN, Sezione di Milano-Bicocca (Italy)], E-mail: firstname.lastname@example.com; Dasgupta, M. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Delenda, Y. [Department de Physique, Faculte des Sciences, Universite de Batna (Algeria)
A quantity that promises to reveal important information on perturbative and non-perturbative QCD dynamics is the azimuthal decorrelation between jets in different hard processes. In order to access this information fixed-order NLO predictions need to be supplemented by resummation of logarithmic terms which are large in the region where the jets are nearly back-to-back in azimuth. In the present Letter we carry out this resummation to next-to-leading logarithmic accuracy explaining the important role played by the recombination scheme in general resummations for such jet observables.
Aespoe Hard Rock Laboratory. Analysis of fracture networks based on the integration of structural and hydrogeological observations on different scales
Energy Technology Data Exchange (ETDEWEB)
Bossart, P. [Geotechnical Inst. Ltd., Bern (Switzerland); Hermanson, Jan [Golder Associates, Stockholm (Sweden); Mazurek, M. [Univ. of Bern (Switzerland)
Fracture networks at Aespoe have been studied for several rock types exhibiting different degrees of ductile and brittle deformation, as well as on different scales. Mesoscopic fault systems have been characterised and classified in an earlier report, this report focuses mainly on fracture networks derived on smaller scales, but also includes mesoscopic and larger scales. The TRUE-1 block has been selected for detailed structural analysis on a small scale due to the high density of relevant information. In addition to the data obtained from core materials, structural maps, BIP data and the results of hydro tests were synthesised to derive a conceptual structural model. The approach used to derive this conceptual model is based on the integration of deterministic structural evidence, probabilistic information and both upscaling and downscaling of observations and concepts derived on different scales. Twelve fracture networks mapped at different sites and scales and exhibiting various styles of tectonic deformation were analysed for fractal properties and structural and hydraulic interconnectedness. It was shown that these analysed fracture networks are not self-similar. An important result is the structural and hydraulic interconnectedness of fracture networks on all scales in the Aespoe rocks, which is further corroborated by geochemical evidence. Due to the structural and hydraulic interconnectedness of fracture systems on all scales at Aespoe, contaminants from waste canisters placed in tectonically low deformation environments would be transported - after having passed through the engineered barriers -from low-permeability fractures towards higher permeability fractures and may thus eventually reach high-permeability features.
Prompt atmospheric neutrino fluxes: perturbative QCD models and nuclear effects
Energy Technology Data Exchange (ETDEWEB)
Bhattacharya, Atri [Department of Physics, University of Arizona,1118 E. 4th St. Tucson, AZ 85704 (United States); Space sciences, Technologies and Astrophysics Research (STAR) Institute,Université de Liège,Bât. B5a, 4000 Liège (Belgium); Enberg, Rikard [Department of Physics and Astronomy, Uppsala University,Box 516, SE-75120 Uppsala (Sweden); Jeong, Yu Seon [Department of Physics and IPAP, Yonsei University,50 Yonsei-ro Seodaemun-gu, Seoul 03722 (Korea, Republic of); National Institute of Supercomputing and Networking, KISTI,245 Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Kim, C.S. [Department of Physics and IPAP, Yonsei University,50 Yonsei-ro Seodaemun-gu, Seoul 03722 (Korea, Republic of); Reno, Mary Hall [Department of Physics and Astronomy, University of Iowa,Iowa City, Iowa 52242 (United States); Sarcevic, Ina [Department of Physics, University of Arizona,1118 E. 4th St. Tucson, AZ 85704 (United States); Department of Astronomy, University of Arizona,933 N. Cherry Ave., Tucson, AZ 85721 (United States); Stasto, Anna [Department of Physics, 104 Davey Lab, The Pennsylvania State University,University Park, PA 16802 (United States)
We evaluate the prompt atmospheric neutrino flux at high energies using three different frameworks for calculating the heavy quark production cross section in QCD: NLO perturbative QCD, k{sub T} factorization including low-x resummation, and the dipole model including parton saturation. We use QCD parameters, the value for the charm quark mass and the range for the factorization and renormalization scales that provide the best description of the total charm cross section measured at fixed target experiments, at RHIC and at LHC. Using these parameters we calculate differential cross sections for charm and bottom production and compare with the latest data on forward charm meson production from LHCb at 7 TeV and at 13 TeV, finding good agreement with the data. In addition, we investigate the role of nuclear shadowing by including nuclear parton distribution functions (PDF) for the target air nucleus using two different nuclear PDF schemes. Depending on the scheme used, we find the reduction of the flux due to nuclear effects varies from 10% to 50% at the highest energies. Finally, we compare our results with the IceCube limit on the prompt neutrino flux, which is already providing valuable information about some of the QCD models.
Prompt atmospheric neutrino fluxes: perturbative QCD models and nuclear effects
Bhattacharya, Atri; Enberg, Rikard; Jeong, Yu Seon; Kim, C. S.; Reno, Mary Hall; Sarcevic, Ina; Stasto, Anna
We evaluate the prompt atmospheric neutrino flux at high energies using three different frameworks for calculating the heavy quark production cross section in QCD: NLO perturbative QCD, k T factorization including low- x resummation, and the dipole model including parton saturation. We use QCD parameters, the value for the charm quark mass and the range for the factorization and renormalization scales that provide the best description of the total charm cross section measured at fixed target experiments, at RHIC and at LHC. Using these parameters we calculate differential cross sections for charm and bottom production and compare with the latest data on forward charm meson production from LHCb at 7 TeV and at 13 TeV, finding good agreement with the data. In addition, we investigate the role of nuclear shadowing by including nuclear parton distribution functions (PDF) for the target air nucleus using two different nuclear PDF schemes. Depending on the scheme used, we find the reduction of the flux due to nuclear effects varies from 10% to 50% at the highest energies. Finally, we compare our results with the IceCube limit on the prompt neutrino flux, which is already providing valuable information about some of the QCD models.
The gluon density of the proton at low x from a QCD analysis of F$_{2}$
Aïd, S; Andrieu, B; Appuhn, R D; Arpagaus, M; Babaev, A; Ban, Y; Baranov, P S; Barrelet, E; Barschke, R; Bartel, Wulfrin; Barth, Monique; Bassler, U; Beck, H P; Behrend, H J; Belousov, A; Berger, C; Bernardi, G; Bernet, R; Bertrand-Coremans, G H; Besançon, M; Beyer, R; Biddulph, P; Bispham, P; Bizot, J C; Blobel, Volker; Borras, K; Botterweck, F; Boudry, V; Braemer, A; Brasse, F W; Braunschweig, W; Brisson, V; Bruncko, Dusan; Brune, C R; Buchholz, R; Buniatian, A Yu; Burke, S; Burton, M; Buschhorn, G W; Bán, J; Bähr, J; Büngener, L; Bürger, J; Büsser, F W; Campbell, A J; Carli, T; Charles, F; Charlet, M; Chernyshov, V; Clarke, D; Clegg, A B; Clerbaux, B; Colombo, M G; Contreras, J G; Cormack, C; Coughlan, J A; Courau, A; Coutures, C; Cozzika, G; Criegee, L; Cussans, D G; Cvach, J; Dagoret, S; Dainton, J B; Dau, W D; Daum, K; David, M; De Wolf, E A; Del Buono, L; Delcourt, B; Di Nezza, P; Dollfus, C; Dowell, John D; Dreis, H B; Droutskoi, A; Duboc, J; Duhm, H; Düllmann, D; Dünger, O; Ebert, J; Ebert, T R; Eckerlin, G; Efremenko, V; Egli, S; Eichenberger, S; Eichler, R; Eisele, Franz; Eisenhandler, Eric F; Ellison, R J; Elsen, E E; Erdmann, M; Erdmann, W; Erlichmann, H; Evrard, E; Favart, L; Fedotov, A; Feeken, D; Felst, R; Feltesse, Joel; Ferencei, J; Ferrarotto, F; Flamm, K; Fleischer, M; Flieser, M; Flügge, G; Fomenko, A; Fominykh, B A; Forbush, M; Formánek, J; Foster, J M; Franke, G; Fretwurst, E; Gabathuler, Erwin; Gabathuler, K; Garvey, J; Gayler, J; Gebauer, M; Gellrich, A; Genzel, H; Gerhards, R; Glazov, A; Goerlach, U; Gogitidze, N; Goldberg, M; Goldner, D; González-Pineiro, B; Gorelov, I V; Goritchev, P A; Grab, C; Greenshaw, T J; Grindhammer, G; Gruber, A; Gruber, C; Grässler, Herbert; Grässler, R; Görlich, L; Haack, J; Haidt, Dieter; Hajduk, L; Hamon, O; Hampel, M; Hapke, M; Haynes, W J; Heatherington, J; Heinzelmann, G; Henderson, R C W; Henschel, H; Herynek, I; Hess, M F; Hildesheim, W; Hill, P; Hiller, K H; Hilton, C D; Hladky, J; Hoeger, K C; Horisberger, R P; Hudgson, V L; Huet, Patrick; Hufnagel, H; Höppner, M; Hütte, M; Ibbotson, M; Itterbeck, H; Jabiol, M A; Jacholkowska, A; Jacobsson, C; Jaffré, M; Janoth, J; Jansen, T; Johnson, D P; Johnson, L; Jung, H; Jönsson, L B; Kalmus, Peter I P; Kant, D; Kaschowitz, R; Kasselmann, P; Kathage, U; Katzy, J M; Kaufmann, H H; Kazarian, S; Kenyon, Ian Richard; Kermiche, S; Keuker, C; Kiesling, C; Klein, M; Kleinwort, C; Knies, G; Ko, W; Kolanoski, H; Kole, F; Kolya, S D; Korbel, V; Korn, M; Kostka, P; Kotelnikov, S K; Krasny, M W; Krehbiel, H; Krämerkämper, T; Krücker, D; Krüger, U P; Krüner-Marquis, U; Kuhlen, M; Kurca, T; Kurzhöfer, J; Kuznik, B; Köhler, T; Köhne, J H; Küster, H; Lacour, D; Lamarche, F; Lander, R; Landon, M P J; Lange, W; Lanius, P; Laporte, J F; Lebedev, A; Lehner, F; Leverenz, C; Levonian, S; Ley, C; Lindström, G; Link, J; Linsel, F; Lipinski, J; List, B; Lobo, G; Loch, P; Lohmander, H; Lomas, J W; Lubimov, V; López, G C; Lüke, D; Magnussen, N; Malinovskii, E I; Mani, S; Maracek, R; Marage, P; Marks, J; Marshall, R; Martens, J; Martin, G; Martin, R D; Martyn, H U; Martyniak, J; Masson, S; Mavroidis, A; Maxfield, S J; McMahon, S J; Mehta, A; Meier, K; Mercer, D; Merz, T; Meyer, C A; Meyer, H; Meyer, J; Migliori, A; Mikocki, S; Milstead, D; Moreau, F; Morris, J V; Mroczko, E; Murín, P; Müller, G; Müller, K; Nagovitsin, V; Nahnhauer, R; Naroska, Beate; Naumann, T; Newman, P R; Newton, D; Neyret, D; Nguyen, H K; Nicholls, T C; Niebergall, F; Niebuhr, C B; Niedzballa, C; Nisius, R; Nowak, G; Noyes, G W; Nyberg-Werther, M; Oakden, M N; Oberlack, H; Obrock, U; Olsson, J E; Ozerov, D; Panaro, E; Panitch, A; Pascaud, C; Patel, G D; Peppel, E; Phillips, J P; Pichler, C; Pitzl, D; Pope, G; Prell, S; Prosi, R; Pérez, E; Rabbertz, K; Raupach, F; Reimer, P; Reinshagen, S; Ribarics, P; Rick, Hartmut; Riech, V; Riedlberger, J; Riess, S; Rietz, M; Rizvi, E; Robertson, S M; Robmann, P; Roloff, H E; Roosen, R; Rosenbauer, K; Rostovtsev, A A; Rouse, F; Royon, C; Rusakov, S V; Rybicki, K; Rylko, R; Rädel, G; Rüter, K; Sahlmann, N; Sankey, D P C; Schacht, P; Schiek, S; Schleif, S; Schleper, P; Schmidt, D; Schmidt, G; Schröder, V; Schuhmann, E; Schwab, B; Schöning, A; Sciacca, G F; Sefkow, F; Seidel, M; Sell, R; Semenov, A A; Shekelian, V I; Shevyakov, I; Shtarkov, L N; Siegmon, G; Siewert, U; Sirois, Y; Skillicorn, Ian O; Smirnov, P; Smith, J R; Solochenko, V; Soloviev, Yu V; Spiekermann, J; Spielman, S; Spitzer, H; Starosta, R; Steenbock, M; Steffen, P; Steinberg, R; Stella, B; Stephens, K; Stier, J; Stiewe, J; Stolze, K; Strachota, J; Straumann, U; Struczinski, W; Stösslein, U; Sutton, J P; Tapprogge, Stefan; Thiebaux, C; Thompson, G; Truöl, P; Turnau, J; Tutas, J; Uelkes, P; Usik, A; Valkár, S; Valkárová, A; Vallée, C; Van Esch, P; Van Mechelen, P; Van den Plas, D; Vartapetian, A H; Vazdik, Ya A; Verrecchia, P; Villet, G; Wacker, K; Wagener, A; Wagener, M; Walther, A; Weber, G; Weber, M; Wegener, D; Wegner, A; Wellisch, H P; West, L R; Willard, S; Winde, M; Winter, G G; Wittek, C; Wright, A E; Wulff, N; Wünsch, E; Yiou, T P; Zarbock, D; Zhang, Z; Zhokin, A S; Zimmer, M; Zimmermann, W; Zomer, F; Zuber, K; Zácek, J; de Roeck, A; von Schlippe, W
We present a QCD analysis of the proton structure function F_2 measured by the H1 experiment at HERA, combined with data from previous fixed target experiments. The gluon density is extracted from the scaling violations of F_2 in the range 2\\cdot 10^{-4}
Results from pQCD for A+A collisions at RHIC & LHC energies
Tuominen, K
This talk will discuss how to compute initial quantites in heavy ion collisions at RHIC (200 AGeV) and at LHC (5500 AGeV) using perturbative QCD (pQCD) by including the next-to-leading order (NLO) corrections and a dynamical determination of the dominant physical scale. The initial numbers are converted into final ones by assuming kinetic thermalization and adiabatic expansion.
Precision QCD measurements at HERA
Directory of Open Access Journals (Sweden)
Pirumov Hayk
Full Text Available A review of recent experimental results on perturbative QCD from the HERA experiments H1 and ZEUS is presented. All inclusive deep inelastic cross sections measured by the H1 and ZEUS collaborations in neutral and charged current unpolarised ep scattering are combined. They span six orders of magnitude in negative four-momentum-transfer squared, Q2, and in Bjorken x. This data set is used as the sole input to NLO and NNLO QCD analyses to determine new sets of parton distributions, HERAPDF2.0, with small experimental uncertainties and an estimate of model and parametrisation uncertainties. Also shown are new results on inclusive jet, dijet and trijet differential cross sections measured in neutral current deep inelastic scattering. The precision jet data is used to extract the strong coupling αs at NLO with small experimental errors.
Innovations in Lattice QCD Algorithms
Energy Technology Data Exchange (ETDEWEB)
Konstantinos Orginos
Lattice QCD calculations demand a substantial amount of computing power in order to achieve the high precision results needed to better understand the nature of strong interactions, assist experiment to discover new physics, and predict the behavior of a diverse set of physical systems ranging from the proton itself to astrophysical objects such as neutron stars. However, computer power alone is clearly not enough to tackle the calculations we need to be doing today. A steady stream of recent algorithmic developments has made an important impact on the kinds of calculations we can currently perform. In this talk I am reviewing these algorithms and their impact on the nature of lattice QCD calculations performed today.
Spectral functions from anisotropic lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Aarts, G.; Allton, C. [Department of Physics, Swansea University, Swansea SA2 8PP, Wales (United Kingdom); Amato, A. [Helsinki Institute of Physics and University of Helsinki, Helsinki (Finland); Evans, W. [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics Universitat Bern, Sidlerstrasse 5, CH-3012 Bern (Switzerland); Giudice, P. [Institut für Theoretische Physik, Universität Münster, D–48149 Münster (Germany); Harris, T. [School of Mathematics, Trinity College, Dublin 2 (Ireland); Kelly, A. [Department of Mathematical Physics, Maynooth University, Maynooth, Co Kildare (Ireland); Kim, S.Y. [Department of Physics, Sejong University, Seoul 143-747 (Korea, Republic of); Lombardo, M.P. [INFN–Laboratori Nazionali di Frascati, I–00044 Frascati (RM) (Italy); Praki, K. [Department of Physics, Swansea University, Swansea SA2 8PP, Wales (United Kingdom); Ryan, S.M. [School of Mathematics, Trinity College, Dublin 2 (Ireland); Skullerud, J.-I. [Department of Mathematical Physics, Maynooth University, Maynooth, Co Kildare (Ireland)
The FASTSUM collaboration has been carrying out lattice simulations of QCD for temperatures ranging from one third to twice the crossover temperature, investigating the transition region, as well as the properties of the Quark Gluon Plasma. In this contribution we concentrate on quarkonium correlators and spectral functions. We work in a fixed scale scheme and use anisotropic lattices which help achieving the desirable fine resolution in the temporal direction, thus facilitating the (ill posed) integral transform from imaginary time to frequency space. We contrast and compare results for the correlators obtained with different methods, and different temporal spacings. We observe robust features of the results, confirming the sequential dissociation scenario, but also quantitative differences indicating that the methods' systematic errors are not yet under full control. We briefly outline future steps towards accurate results for the spectral functions and their associated statistical and systematic errors.
KMI Lattice Project on 16-Flavor QCD
Aoki, Yasumichi; Aoyama, Tatsumi; Kurachi, Masafumi; Maskawa, Toshihide; Nagai, Kei-Ichi; Ohki, Hiroshi; Shibata, Aakihiro; Yamawaki, Koichi; Yamazaki, Takeshi
It is well known that the SU(3) gauge theory with the fundamental 16-flavor fermion is governed by a non-trivial infrared fixed point in the 2-loop perturbation theory, while the theory has not been well investigated by non-perturbative lattice simulations. We investigate properties of 16-flavor QCD by lattice simulation with highly improved action setup (HISQ/tree) at two lattice spacings. We present preliminary results for the mass of the lightest pseudoscalar meson at non-zero fermion mass. We discuss the (finite-size) hyperscaling of our data, the mass anomalous dimension extracted from the scaling, and comparison of the anomalous dimension with the perturbation theory.
Lattice QCD: A Brief Introduction
Meyer, H. B.
A general introduction to lattice QCD is given. The reader is assumed to have some basic familiarity with the path integral representation of quantum field theory. Emphasis is placed on showing that the lattice regularization provides a robust conceptual and computational framework within quantum field theory. The goal is to provide a useful overview, with many references pointing to the following chapters and to freely available lecture series for more in-depth treatments of specifics topics.
Rabbertz, Klaus
In view of the approaching LHC operation the feasibility and accuracy of QCD measurements with the CMS experiment at the Large Hadron Collider (LHC) involving hadrons and jets are discussed. This summary is based on analyses performed at CMS for center-of-mass energies of 10 as well as 14 TeV assuming event numbers ranging from some days of data taking up to 100/pb of integrated luminosity with proton-proton collisions.
Nucleon structure from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Dinter, Simon
In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a{sup 2}) discretization effects.
Energy Technology Data Exchange (ETDEWEB)
Davier, M
Hadronic decays of the {tau} lepton provide a clean source to study hadron dynamics in an energy regime dominated by resonances, with the interesting information captured in the spectral functions. Recent results on exclusive channels are reviewed. Inclusive spectral functions are the basis for QCD analyses, delivering an accurate determination of the strong coupling constant and quantitative information on nonperturbative contributions. Strange decays yield a determination of the strange quark mass. (author)
Energy Technology Data Exchange (ETDEWEB)
DeGrand, T. [Univ. of Colorado, Boulder, CO (United States). Dept. of Physics
These lectures provide an introduction to lattice methods for nonperturbative studies of Quantum Chromodynamics. Lecture 1: Basic techniques for QCD and results for hadron spectroscopy using the simplest discretizations; lecture 2: Improved actions--what they are and how well they work; lecture 3: SLAC physics from the lattice-structure functions, the mass of the glueball, heavy quarks and {alpha}{sub s} (M{sub z}), and B-{anti B} mixing. 67 refs., 36 figs.
Hadron melting and QCD thermodynamics
Jakovac, A.
We study in this paper mechanisms of hadron melting based on the spectral representation of hadronic quantum channels, and examine the hadron width dependence of the pressure. The findings are applied to a statistical hadron model of QCD thermodynamics, where hadron masses are distributed by the Hagedorn model and a uniform mechanism for producing hadron widths is assumed. According to this model the hadron - quark gluon plasma transition occurs at $T\\approx 200$-250 MeV, the numerically obse...
Two-color lattice QCD with staggered quarks
Energy Technology Data Exchange (ETDEWEB)
Scheffler, David
The study of quantum chromodynamics (QCD) at finite temperature and density provides important contributions to the understanding of strong-interaction matter as it is present e.g. in nuclear matter and in neutron stars or as produced in heavy-ion collision experiments. Lattice QCD is a non-perturbative approach, where equations of motion for quarks and gluons are discretized on a finite space-time lattice. The method successfully describes the behavior of QCD in the vacuum and at finite temperature, however it cannot be applied to finite baryon density due to the fermion sign problem. Various QCD-like theories, that offer to draw conclusions about QCD, allow simulations also at finite densities. In this work we investigate two-color QCD as a popular example of a QCD-like theory free from the sign problem with methods from lattice gauge theory. For the generation of gauge configurations with two dynamical quark flavors in the staggered formalism with the ''rooting trick'' we apply the Rational Hybrid Monte Carlo (RHMC) algorithm. We carry out essential preparatory work for future simulations at finite density. As a start, we concentrate on the calculation of the effective potential for the Polyakov loop, which is an order parameter for the confinement-deconfinement transition, in dependence of the temperature and quark mass. It serves as an important input for effective models of QCD. We obtain the effective potential via the histogram method from local distributions of the Polyakov loop. To study the influence of dynamical quarks on gluonic observables, the simulations are performed with large quark masses and are compared to calculations in the pure gauge theory. In the second part of the thesis we examine aspects of the chiral phase transition along the temperature axis. The symmetry group of chiral symmetry in two-color QCD is enlarged to SU(2N{sub f}). Discretized two-color QCD in the staggered formalism exhibits a chiral symmetry breaking
Hadron structure from lattice QCD
Constantinou, Martha
More than 99 per cent of the mass of the visible world resides in hadrons which are bound states of quarks and gluons, the fundamental constituents of Quantum Chromodynamics (QCD). The proton is at the heart of the hadronic matter and is an ideal laboratory for studying the QCD dynamics. Lattice QCD (LQCD) is a powerful non-perturbative tool for the ab inition calculation of hadron observables that are well determined experimentally, or not easily accessible in experiment. Progress in the simulation of LQCD has been impressive, mainly due to improvements in the algorithms, development of new techniques and increase in computational power, that have enabled simulations to be carried out at parameters very close to their physical values. In this talk I will present recent developments in hadron structure focusing on achievements in the evaluation of nucleon quantities, such as the nucleon charges, form factors, and gluonic contributions, in view of simulations close or at the physical value of the pion mass. I will also discuss the enormous efforts towards a new direct approach to compute quark parton distributions functions on the lattice. Work partly supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, within the framework of the TMD Topical Collaboration.
Moriond QCD 2013 Experimental Summary
Energy Technology Data Exchange (ETDEWEB)
Denisov, Dmitri [Fermilab
The article presents experimental highlights of Moriond 2013 QCD conference. This was fantastic conference and the first Moriond QCD since the discovery of the Higgs boson. Many new results about its properties have been presented at the conference with Higgs-like particle becoming a Higgs as it properties match expected for the Higgs boson pretty well. There were many new results presented in all experimental areas including QCD, elecroweak, studies of the top, bottom and charm quarks, searches for physics beyond Standard Model as well as studies of the heavy ion collisions. 56 experimental talks have been presented at the conference and it is impossible to cover each result in the summary, so highlights are limited to what I was able to present in my summary talk presented on March 16 2013. The proceedings of the conference cover in depth all talks presented and I urge you to get familiar with all of them. Theoretical Summary of the conference was given by Michelangelo Mangano, so theory talks are not covered in the article.
Baryogenesis from strong CP violation and the QCD axion.
Servant, Géraldine
We show that strong CP violation from the QCD axion can be responsible for the matter antimatter asymmetry of the Universe in the context of cold electroweak baryogenesis if the electroweak phase transition is delayed below the GeV scale. This can occur naturally if the Higgs couples to a O(100) GeV dilaton, as expected in some models where the Higgs is a pseudo-Nambu-Goldstone boson of a new strongly interacting sector at the TeV scale. The existence of such a second scalar resonance with a mass and properties similar to the Higgs boson will soon be tested at the LHC. In this context, the QCD axion would not only solve the strong CP problem, but also the matter antimatter asymmetry and dark matter.
Strongly interacting matter from holographic QCD model
Directory of Open Access Journals (Sweden)
Chen Yidian
Full Text Available We introduce the 5-dimension dynamical holographic QCD model, which is constructed in the graviton-dilaton-scalar framework with the dilaton background field Φ and the scalar field X responsible for the gluodynamics and chiral dynamics, respectively. We review our results on the hadron spectra including the glueball and light meson spectra, QCD phase transitions and transport properties in the framework of the dynamical holographic QCD model.
Topology in dynamical lattice QCD simulations
Energy Technology Data Exchange (ETDEWEB)
Gruber, Florian
Lattice simulations of Quantum Chromodynamics (QCD), the quantum field theory which describes the interaction between quarks and gluons, have reached a point were contact to experimental data can be made. The underlying mechanisms, like chiral symmetry breaking or the confinement of quarks, are however still not understood. This thesis focuses on topological structures in the QCD vacuum. Those are not only mathematically interesting but also closely related to chiral symmetry and confinement. We consider methods to identify these objects in lattice QCD simulations. Based on this, we explore the structures resulting from different discretizations and investigate the effect of a very strong electromagnetic field on the QCD vacuum.
Disconnected Diagrams in Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Gambhir, Arjun [College of William and Mary, Williamsburg, VA (United States)
In this work, we present state-of-the-art numerical methods and their applications for computing a particular class of observables using lattice quantum chromodynamics (Lattice QCD), a discretized version of the fundamental theory of quarks and gluons. These observables require calculating so called \\disconnected diagrams" and are important for understanding many aspects of hadron structure, such as the strange content of the proton. We begin by introducing the reader to the key concepts of Lattice QCD and rigorously define the meaning of disconnected diagrams through an example of the Wick contractions of the nucleon. Subsequently, the calculation of observables requiring disconnected diagrams is posed as the computationally challenging problem of finding the trace of the inverse of an incredibly large, sparse matrix. This is followed by a brief primer of numerical sparse matrix techniques that overviews broadly used methods in Lattice QCD and builds the background for the novel algorithm presented in this work. We then introduce singular value deflation as a method to improve convergence of trace estimation and analyze its effects on matrices from a variety of fields, including chemical transport modeling, magnetohydrodynamics, and QCD. Finally, we apply this method to compute observables such as the strange axial charge of the proton and strange sigma terms in light nuclei. The work in this thesis is innovative for four reasons. First, we analyze the effects of deflation with a model that makes qualitative predictions about its effectiveness, taking only the singular value spectrum as input, and compare deflated variance with different types of trace estimator noise. Second, the synergy between probing methods and deflation is investigated both experimentally and theoretically. Third, we use the synergistic combination of deflation and a graph coloring algorithm known as hierarchical probing to conduct a lattice calculation of light disconnected matrix elements
High Energy Description of Processes with Multiple Hard Jets
Andersen, Jeppe R
High Energy Jets (HEJ) is a new framework for approximating the all-order perturbative corrections to multi-jet processes, with a focus on the hard, wide-angle QCD emissions, which underpins the perturbative description of hard jets. In this contribution we review the basic concepts of HEJ, and present some new predictions for observables in dijet-production, and for W-boson production in association with at least 3 jets.
High Energy Description of Processes with Multiple Hard Jets
Energy Technology Data Exchange (ETDEWEB)
Andersen, Jeppe R. [Theory Division, Physics Department, CERN, CH-1211 Geneva 23 (Switzerland); Smillie, Jennifer M. [Department of Physics, UCL, Gower Street, WC1E 6BT (United Kingdom)
High Energy Jets (HEJ) is a new framework for approximating the all-order perturbative corrections to multi-jet processes, with a focus on the hard, wide-angle QCD emissions, which underpins the perturbative description of hard jets. In this contribution we review the basic concepts of HEJ, and present some new predictions for observables in dijet-production, and for W-boson production in association with at least 3 jets.
QCD corrections to ZZ production in gluon fusion at the LHC
Caola, Fabrizio; Röntsch, Raoul; Tancredi, Lorenzo
We compute the next-to-leading order QCD corrections to the production of two Z-bosons in the annihilation of two gluons at the LHC. Being enhanced by a large gluon flux, these corrections provide distinct and, potentially, the dominant part of the N$^3$LO QCD contributions to Z-pair production in proton collisions. The $gg \\to ZZ$ annihilation is a loop-induced process that receives the dominant contribution from loops of five light quarks, that are included in our computation in the massless approximation. We find that QCD corrections increase the $gg \\to ZZ$ production cross section by ${\\cal O}(50\\%-100\\%)$ depending on the values of the renormalization and factorization scales used in the leading order computation, and the collider energy. The large corrections to $gg \\to ZZ$ channel increase the $pp \\to ZZ$ cross section by about six to eight percent, exceeding the estimated theoretical uncertainty of the recent NNLO QCD calculation.
QCD analysis of heavy quarks production in hadronic collisions
Energy Technology Data Exchange (ETDEWEB)
Mirjalili, A. [Physics Department, Yazd University, Yazd (Iran, Islamic Republic of); Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O.Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: email@example.com; Khorramian, Ali. N. [Physics Department, Semnan University, Semnan (Iran, Islamic Republic of); Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O.Box 19395-5531, Tehran (Iran, Islamic Republic of); Atashbar Tehrani, S. [Physics Department, Persian Gulf University, Boushehr (Iran, Islamic Republic of); Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O.Box 19395-5531, Tehran (Iran, Islamic Republic of)
The problem of renormalization scheme dependence in QCD perturbation theory remains on obstacle to making precise tests of the theory. The renormalization scale dependence of dimensionless physical QCD observable, depending on a single energy scale Q, can be avoided provided that all ultraviolet logarithms which build the physical energy dependence on Q are resummed. This was termed complete Renormalization Group improvement(CORGI). This argument can be extended to processes involving factorization of operator matrix elements and coefficient functions. We are trying to employ the idea of CORGI approach on analyzing of heavy quarks production in hadron collisions. There is a sizable and systematic discrepancy between experimental data on the bb-bar production in pp-bar , {gamma}p and {gamma}{gamma} collisions and existing theoretical calculations within perturbative QCD. One suggested way to cope with this discrepancy is to employ the CORGI approach in which one should perform a resummation to all-orders of renormalization and factorization group -predictable terms at each order of perturbation theory. Then the scales dependence will be avoided and it is expected that the mentioned discrepancy is reduced significantly.
Novel QCD Phenomena at the LHC: The Ridge, Digluon-Initiated Subprocesses, Direct Reactions, Non-Universal Antishadowing, and Forward Higgs Production
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC
I discuss a number of novel tests of QCD at the LHC, measurements which can illuminate fundamental features of hadron physics. I also review the "Principle of Maximum Conformality" (PMC) which systematically sets the renormalization scale order-by-order in pQCD, eliminating an unnecessary theoretical uncertainty. The PMC allows LHC experiments to test QCD much more precisely, and the sensitivity of LHC measurements to physics beyond the Standard Model is increased.
Consistent Perturbative Fixed Point Calculations in QCD and Supersymmetric QCD
DEFF Research Database (Denmark)
Ryttov, Thomas A.
We suggest how to consistently calculate the anomalous dimension $\\gamma_*$ of the $\\bar{\\psi}\\psi$ operator in finite order perturbation theory at an infrared fixed point for asymptotically free theories. If the $n+1$ loop beta function and $n$ loop anomalous dimension are known then $\\gamma_*$ ...... throughout the entire conformal window. We finally compute $\\gamma_*$ through $O(\\Delta_f^3)$ for QCD and a variety of other non-supersymmetric fermionic gauge theories. Small values of $\\gamma_*$ are observed for a large range of flavors....
The condensation of the corona for the correlation between the hard X-ray photon index Γ and the reflection scaling factor ℜ in active galactic nuclei
Qiao, Erlin; Liu, B. F.
Observationally, it is found that there is a strong correlation between the hard X-ray photon index Γ and the Compton reflection scaling factor ℜ in active galactic nuclei. In this paper, we propose that the Γ - ℜ correlation can be explained within the framework of the condensation of the hot corona on to the cold accretion disc around a supermassive black hole. In the model, it is presumed that, initially, a vertically extended hot gas (corona) is supplied to the central supermassive black hole by capturing the interstellar medium and stellar wind. In this scenario, when the initial mass accretion rate \\dot{M}/ \\dot{M}_Edd ≳ 0.01, at a critical radius rd, part of the hot gas begins to condense on to the equatorial disc plane of the black hole, forming an inner cold accretion disc. Then, the matter is accreted in the form of a disc-corona structure extending down to the innermost stable circular orbits of the black hole. The size of the inner disc is determined by the initial mass accretion rate. With the increase of the initial mass accretion rate, the size of the inner disc increases, which results in both the increase of the Compton reflection scaling factor ℜ and the increase of the hard X-ray photon index Γ. By comparing with a sample of Seyfert galaxies with well-fitted X-ray spectra, it is found that our model can roughly explain the observations. Finally, we discuss the possibility of applying our model to high-mass X-ray binaries, which are believed to be fuelled by hot winds from the companion stars.
Energy Technology Data Exchange (ETDEWEB)
Bolzoni, P.
In this PhD thesis, we analyze and generalize the renormalization group approach to the resummation of large logarithms in the perturbative expansion due to soft and collinear multiparton emissions. In particular, we present a generalization of this approach to prompt photon production. It is interesting to see that also with the more intricate two-scale kinematics that characterizes prompt photon production in the soft limit, it remains true that resummation simply follows from general kinematic properties of the phase space. Also, this approach does not require a separate treatment of individual colour structures when more than one colour structure contributes to fixed order results. However, the resummation formulae obtained here turn out to be less predictive than previous results: this depends on the fact that here neither specific factorization properties of the cross section in the soft limit is assumed, nor that soft emission satisfies eikonal-like relations. We also derive resumation formulae to all logarithmic accuracy and valid for all values of rapidity for the prompt photon production and the Drell-Yan rapidity distributions. We show that for the fixed-target experiment E866/NuSea, the NLL resummation corrections are comparable to NLO fixed-order corrections and are crucial to obtain agreement with the data. Finally we outline also possible future applications of the renormalization group approach. (orig.)
Global QCD Analysis of the Nucleon Tensor Charge with Lattice QCD Constraints
Shows, Harvey, III; Melnitchouk, Wally; Sato, Nobuo
By studying the parton distribution functions (PDFs) of a nucleon, we probe the partonic scale of nature, exploring what it means to be a nucleon. In this study, we are interested in the transversity PDF-the least studied of the three collinear PDFs. By conducting a global analysis on experimental data from semi-inclusive deep inelastic scattering (SIDIS), as well as single-inclusive e+e- annihilation (SIA), we extract the fit parameters needed to describe the transverse moment dependent (TMD) transversity PDF, as well as the Collins fragmentation function. Once the collinear transversity PDF is obtained by integrating the extracted TMD PDF, we wish to resolve discrepancies between lattice QCD calculations and phenomenological extractions of the tensor charge from data. Here we show our results for the transversity distribution and tensor charge. Using our method of iterative Monte Carlo, we now have a more robust understanding of the transversity PDF. With these results we are able to progress in our understanding of TMD PDFs, as well as testify to the efficacy of current lattice QCD calculations. This work is made possible through support from NSF award 1659177 to Old Dominion University.
Aspects of QCD Dynamics from String Theory
Hashimoto, A; Hashimoto, Akikazu; Oz, Yaron
We study dynamical aspects of large N QCD_4 via supergravity on Anti de Sitter black hole geometry. We compute the mass spectrum, the topological susceptibility and the gluon condensate and make a comparison to lattice simulations. We present analogous results for QCD_3.
Academic Training Lectures - QCD for Postgraduates
Maureen Prola-Tessaur
by Giulia Zanderighi (University of Oxford) Monday 12 to Friday 16 April 2010 From 11:00 to 12:00 - Main Auditorium, Bldg. 500-1-001 Monday 12 - Modern QCD - Lecture 1 Starting from the QCD Lagrangian we will revisit some basic QCD concepts and derive fundamental properties like gauge invariance and isospin symmetry and will discuss the Feynman rules of the theory. We will then focus on the gauge group of QCD and derive the Casimirs CF and CA and some useful color identities. Tuesday 13 - Modern QCD - Lecture 2 We will start discussing the matter content of the theory and revisit the experimental measurements that led to the discovery of quarks. We will then consider a classic QCD observable, the R-ratio, and use it to illustrate the appearance of UV divergences and the need to renormalize the coupling constant of QCD. We will then discuss asymptotic freedom and confinement. Finally, we will examine a case where soft and collinear infrared divergences appear, will discuss the soft approximation in QCD ...
Nuclear Physics from Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
William Detmold, Silas Beane, Konstantinos Orginos, Martin Savage
We review recent progress toward establishing lattice Quantum Chromodynamics as a predictive calculational framework for nuclear physics. A survey of the current techniques that are used to extract low-energy hadronic scattering amplitudes and interactions is followed by a review of recent two-body and few-body calculations by the NPLQCD collaboration and others. An outline of the nuclear physics that is expected to be accomplished with Lattice QCD in the next decade, along with estimates of the required computational resources, is presented.
PT Symmetry and QCD: Finite Temperature and Density
Directory of Open Access Journals (Sweden)
Michael C. Ogilvie
Full Text Available The relevance of PT symmetry to quantum chromodynamics (QCD, the gauge theory of the strong interactions, is explored in the context of finite temperature and density. Two significant problems in QCD are studied: the sign problem of finite-density QCD, and the problem of confinement. It is proven that the effective action for heavy quarks at finite density is PT-symmetric. For the case of 1+1 dimensions, the PT-symmetric Hamiltonian, although not Hermitian, has real eigenvalues for a range of values of the chemical potential μ, solving the sign problem for this model. The effective action for heavy quarks is part of a potentially large class of generalized sine-Gordon models which are non-Hermitian but are PT-symmetric. Generalized sine-Gordon models also occur naturally in gauge theories in which magnetic monopoles lead to confinement. We explore gauge theories where monopoles cause confinement at arbitrarily high temperatures. Several different classes of monopole gases exist, with each class leading to different string tension scaling laws. For one class of monopole gas models, the PT-symmetric affine Toda field theory emerges naturally as the effective theory. This in turn leads to sine-law scaling for string tensions, a behavior consistent with lattice simulations.
Dispersive approach to QCD and inclusive τ lepton hadronic decay
Nesterenko, A. V.
The dispersive approach to QCD is applied to the study of the inclusive τ lepton hadronic decay. This approach provides the unified integral representations for the hadronic vacuum polarization function, related R function, and Adler function. These representations account for the intrinsically nonperturbative constraints, which originate in the kinematic restrictions on the functions on hand, and retain the effects due to hadronization, which play a valuable role in the analysis of the strong interaction processes at low energies. The dispersive approach proves to be capable of describing recently updated ALEPH and OPAL experimental data on inclusive τ lepton hadronic decay in vector and axial-vector channels. The vicinity of values of the QCD scale parameter obtained in both channels testifies to the potential ability of the developed approach to describe the aforementioned data in a self-consistent way.
Cosmologically safe QCD axion without fine-tuning
Energy Technology Data Exchange (ETDEWEB)
Yamada, Masaki [Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Tokyo Univ., Chiba (Japan). Inst. for Cosmic Ray Research; DESY Hamburg (Germany); Yanagida, Tsutomu T.; Yonekura, Kazuya [Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS
Although QCD axion models are widely studied as solutions to the strong CP problem, they generically confront severe fine-tuning problems to guarantee the anomalous PQ symmetry. In this letter, we propose a simple QCD axion model without any fine-tunings. We introduce an extra dimension and a pair of extra quarks living on two branes separately, which is also charged under a bulk Abelian gauge symmetry. We assume a monopole condensation on our brane at an intermediate scale, which implies that the extra quarks develop the chiral symmetry breaking and the PQ symmetry is broken. In contrast to the original Kim's model, our model explains the origin of the PQ symmetry thanks to the extra dimension and avoids the cosmological domain wall problem because of the chiral symmetry breaking in the Abelian gauge theory.
From QCD to nuclear matter saturation
Energy Technology Data Exchange (ETDEWEB)
Ericson, Magda [Universite de Lyon, Univ. Lyon 1, CNRS/IN2P3, IPN Lyon, F-69622 Villeurbanne Cedex (France)]|[Theory division, CERN, CH-12111 Geneva (Switzerland); Chanfray, Guy [Universite de Lyon, Univ. Lyon 1, CNRS/IN2P3, IPN Lyon, F-69622 Villeurbanne Cedex (France)
We discuss a relativistic chiral theory of nuclear matter with {sigma} and {omega} exchange using a formulation of the {sigma} model in which all the chiral constraints are automatically fulfilled. We establish a relation between the nuclear response to the scalar field and the QCD one which includes the nucleonic parts. It allows a comparison between nuclear and QCD information. Going beyond the mean field approach we introduce the effects of the pion loops supplemented by the short-range interaction. The corresponding Landau-Migdal parameters are taken from spin-isospin physics results. The parameters linked to the scalar meson exchange are extracted from lattice QCD results. These inputs lead to a reasonable description of the saturation properties, illustrating the link between QCD and nuclear physics. We also derive from the corresponding equation of state the density dependence of the quark condensate and of the QCD susceptibilities. (authors)
Meson Spectroscopy from QCD - Project Results
Energy Technology Data Exchange (ETDEWEB)
Dudek, Jozef [Old Dominion Univ., Norfolk, VA (United States)
Highlights of the research include: the determination of the form of the lowest energy gluonic excitation within QCD and the spectrum of hybrid hadrons which follows; the first calculation of the spectrum of hybrid baryons within a first-principles approach to QCD; a detailed mapping out of the phase-shift of elastic ππ scattering featuring the ρ resonance at two values of the light quark mass within lattice QCD; the first (and to date, only) determinations of coupled-channel meson-meson scattering within first-principles QCD; the first (and to date, only) determinations of the radiative coupling of a resonant state, the ρ appearing in πγ→ππ; the first (and to date, only) determination of the properties of the broad σ resonance in elastic ππ scattering within QCD without unjustified approximations.
Lattice QCD Calculation of Nucleon Structure
Energy Technology Data Exchange (ETDEWEB)
Liu, Keh-Fei [University of Kentucky, Lexington, KY (United States). Dept. of Physics and Astronomy; Draper, Terrence [University of Kentucky, Lexington, KY (United States). Dept. of Physics and Astronomy
It is emphasized in the 2015 NSAC Long Range Plan that "understanding the structure of hadrons in terms of QCD's quarks and gluons is one of the central goals of modern nuclear physics." Over the last three decades, lattice QCD has developed into a powerful tool for ab initio calculations of strong-interaction physics. Up until now, it is the only theoretical approach to solving QCD with controlled statistical and systematic errors. Since 1985, we have proposed and carried out first-principles calculations of nucleon structure and hadron spectroscopy using lattice QCD which entails both algorithmic development and large-scale computer simulation. We started out by calculating the nucleon form factors -- electromagnetic, axial-vector, πNN, and scalar form factors, the quark spin contribution to the proton spin, the strangeness magnetic moment, the quark orbital angular momentum, the quark momentum fraction, and the quark and glue decomposition of the proton momentum and angular momentum. The first round of calculations were done with Wilson fermions in the `quenched' approximation where the dynamical effects of the quarks in the sea are not taken into account in the Monte Carlo simulation to generate the background gauge configurations. Beginning in 2000, we have started implementing the overlap fermion formulation into the spectroscopy and structure calculations. This is mainly because the overlap fermion honors chiral symmetry as in the continuum. It is going to be more and more important to take the symmetry into account as the simulations move closer to the physical point where the u and d quark masses are as light as a few MeV only. We began with lattices which have quark masses in the sea corresponding to a pion mass at ~ 300 MeV and obtained the strange form factors, charm and strange quark masses, the charmonium spectrum and the Ds meson decay constant fDs, the strangeness and charmness, the meson mass
On the NNLO QCD corrections to single-top production at the LHC
Directory of Open Access Journals (Sweden)
Mathias Brucherseifer
Full Text Available We present a fully-differential calculation of the NNLO QCD corrections to the t-channel mechanism for producing single top quarks at the LHC. We work in the structure function approximation, computing QCD corrections to the light- and heavy-quark lines separately and neglecting the dynamical cross-talk between the two. The neglected contribution, which appears at NNLO for the first time, is color-suppressed and is expected to be sub-dominant. Within this approximation, we find that, for the total cross section, NNLO QCD corrections are in the few percent range and, therefore, are comparable to NLO QCD corrections. We also find that the scale independence of the theoretical prediction for single-top production improves significantly once NNLO QCD corrections are included. Furthermore, we show how these results change if a cut on the transverse momentum of the top quark is applied and derive the NNLO QCD prediction for the ratio of single top and single anti-top production cross sections at the 8 TeV LHC.
Hadron physics from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Schaefer, Andreas [Regensburg Univ. (Germany). Inst. for Theoretical Physics
Particle physics experiments at modern high luminosity particle accelerators achieve orders of magnitude higher count rates than what was possible ten or twenty years ago. This extremely large statistics allows to draw far reaching conclusions even from minute signals, provided that these signals are well understood by theory. This is, however, ever more difficult to achieve. Presently, technical and scientific progress in general and experimental progress in particle physics in particular, shows typically an exponential growth rate. For example, data acquisition and analysis are, among many other factor, driven by the development of ever more efficient computers and thus by Moore's law. Theory has to keep up with this development by also achieving an exponential increase in precision, which is only possible using powerful computers. This is true for both types of calculations, analytic ones as, e.g., in quantum field perturbation theory, and purely numerical ones as in Lattice QCD. As stated above such calculations are absolutely indispensable to make best use of the extremely costly large particle physics experiments. Thus, it is economically reasonable to invest a certain percentage of the cost of accelerators and experiments in related theory efforts. The basic ideas behind Lattice QCD simulations are the following: Because quarks and gluons can never be observed individually but are always ''confined'' into colorless hadrons, like the proton, all quark-gluon states can be expressed in two different systems of basis states, namely in a quark-gluon basis and the basis of hadron states. The proton, e.g., is an eigenstate of the latter, a specific quark-gluon configuration is part of the former. In the quark-gluon basis a physical hadron, like a proton, is given by an extremely complicated multi-particle wave function containing all effects of quantum fluctuations. This state is so complicated that it is basically impossible to model it
Theta dependence in holographic QCD
Energy Technology Data Exchange (ETDEWEB)
Bartolini, Lorenzo [Dipartimento di Fisica "E. Fermi' , Università di Pisa and INFN, Sezione di Pisa,Largo B. Pontecorvo 3, I-56127 Pisa (Italy); Bigazzi, Francesco [INFN, Sezione di Firenze,Via G. Sansone 1, I-50019 Sesto Fiorentino (Firenze) (Italy); Bolognesi, Stefano [Dipartimento di Fisica "E. Fermi' , Università di Pisa and INFN, Sezione di Pisa,Largo B. Pontecorvo 3, I-56127 Pisa (Italy); Cotrone, Aldo L. [INFN, Sezione di Firenze,Via G. Sansone 1, I-50019 Sesto Fiorentino (Firenze) (Italy); Dipartimento di Fisica e Astronomia, Università di Firenze,Via G. Sansone 1, I-50019 Sesto Fiorentino (Firenze) (Italy); Manenti, Andrea [Institute of Physics, EPFL,Rte de la Sorge, BSP 728, CH-1015 Lausanne (Switzerland)
We study the effects of the CP-breaking topological θ-term in the large N{sub c} QCD model by Witten, Sakai and Sugimoto with N{sub f} degenerate light flavors. We first compute the ground state energy density, the topological susceptibility and the masses of the lowest lying mesons, finding agreement with expectations from the QCD chiral effective action. Then, focusing on the N{sub f}=2 case, we consider the baryonic sector and determine, to leading order in the small θ regime, the related holographic instantonic soliton solutions. We find that while the baryon spectrum does not receive O(θ) corrections, this is not the case for observables like the electromagnetic form factor of the nucleons. In particular, it exhibits a dipole term, which turns out to be vector-meson dominated. The resulting neutron electric dipole moment, which is exactly the opposite as that of the proton, is of the same order of magnitude of previous estimates in the literature. Finally, we compute the CP-violating pion-nucleon coupling constant ḡ{sub πNN}, finding that it is zero to leading order in the large N{sub c} limit.
The impacts of low-cost treatment options upon scale formation potential in remote communities reliant on hard groundwaters. A case study: Northern Territory, Australia
Energy Technology Data Exchange (ETDEWEB)
Kinsela, Andrew S., E-mail: email@example.com [UNSW Water Research Centre, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia); Jones, Adele M., E-mail: email@example.com [UNSW Water Research Centre, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia); Collins, Richard N., E-mail: firstname.lastname@example.com [UNSW Water Research Centre, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia); Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Waite, T. David, E-mail: firstname.lastname@example.com [UNSW Water Research Centre, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia)
The majority of small, remote communities within the Northern Territory (NT) in Central Australia are reliant on groundwater as their primary supply of domestic, potable water. Saturation indices for a variety of relevant minerals were calculated using available thermodynamic speciation codes on collected groundwater data across the NT. These saturation indices were used to assess the theoretical formation of problematic mineral-scale, which manifests itself by forming stubborn coatings on domestic appliances and fixtures. The results of this research show that 63% of the measured sites within the NT have the potential to form calcium carbonate (CaCO{sub 3}) scale, increasing to 91% in arid, central regions. The data also suggests that all groundwaters are over-saturated with respect to amorphous calcium-bridged ferric-silica polymers, based on the crystalline mineral index (Ca{sub 3}Fe{sub 2}Si{sub 3}O{sub 12}), although the quantitative impact of this scale is limited by low iron concentrations. An assessment of possible low-cost/low-technology management options was made, including; lowering the temperature of hot-water systems, diluting groundwater with rainwater and modifying the pH of the source water. Source water pH modification (generally a reduction to pH 7.0) was shown to clearly alleviate potential carbonate-based scale formation, over and above the other two options, albeit at a greater technical and capital expense. Although low-cost/low-technology treatment options are unlikely to remove severe scale-related issues, their place in small, remote communities with minor scale problems should be investigated further, owing to the social, technical and capital barriers involved with installing advanced treatment plants (e.g. reverse osmosis) in such locations. - Highlights: Black-Right-Pointing-Pointer Scaling potential of small communities reliant on hard groundwaters were analysed. Black-Right-Pointing-Pointer Oversaturation of carbonate- and silica
Hard Probes in Heavy-Ion Physics
Renk, Thorsten
The aim of ultrarelativistic heavy ion physics is to study collectivity and thermodynamics of Quantum Chromodynamics (QCD) by creating a transient small volume of matter with extreme density and temperature. There is experimental evidence that most of the particles created in such a collision form indeed a thermalized system characterized by collective response to pressure gradients. However, a numerically small subset of high transverse momentum ($P_T$) processes takes place independent of the bulk, with the outgoing partons subsequently propagating through the bulk medium. Understanding the modification of such 'hard probes' by the bulk medium is an important part of the efforts to determine the properties of hot and dense QCD matter. In this paper, current developments are reviewed.
Probing QCD at the Highest $Q^2$ Deep Inelastic Scattering
Ferrando, J
Recent results from the HERA ep collider are reviewed in these proceedings. The results are from measurements that probe QCD at high-energy scales, as defined by $Q^2$, the four-momentum-transfer squared of the collisions. These cross-section measurements provide information about the parton distribution functions (PDFs) of the proton and can be used to constrain global fits of these PDFs. Recent measurements of the strong coupling $\\alpha_S$ and jet substructure from HERA at similar energy scales are also reviewed.
The AdS/QCD Correspondence and Exclusive Processes
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; de Teramond, Guy F.; /Costa Rica U.; Deur, Alexandre; /Jefferson Lab
The AdS/CFT correspondence between theories in AdS space and conformal field theories in physical space-time provides an analytic, semi-classical, color-confining model for strongly-coupled QCD. The soft-wall AdS/QCD model modified by a positive-sign dilaton metric leads to a remarkable one-parameter description of nonperturbative hadron dynamics at zero quark mass, including a zero-mass pion and a Regge spectrum of linear trajectories with the same slope in orbital angular momentum L and radial quantum number n for both mesons and baryons. One also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS}(q) and its {beta}-function which agrees with the effective coupling {alpha}{sub ga} extracted from the Bjorken sum rule. Light-front holography, which connects the fifth-dimensional coordinate of AdS space z to an invariant impact separation variable {zeta}, allows one to compute the analytic form of the frame-independent light-front wavefunctions, the fundamental entities which encode hadron properties as well as decay constants, form factors, deeply virtual Compton scattering, exclusive heavy hadron decays and other exclusive scattering amplitudes. One thus obtains a relativistic description of hadrons in QCD at the amplitude level with dimensional counting for hard exclusive reactions at high momentum transfer. As specific examples we discuss the behavior of the pion and nucleon form factors in the space-like and time-like regions. We also review the phenomenology of exclusive processes including some anomalous empirical results.
Confinement in Polyakov gauge and the QCD phase diagram
Energy Technology Data Exchange (ETDEWEB)
Marhauser, Marc Florian
We investigate Quantum Chromodynamics (QCD) in the framework of the functional renormalisation group (fRG). Thereby describing the phase transition from the phase with confined quarks into the quark-gluon-plasma phase. We focus on a physical gauge in which the mechanism driving the phase transition is discernible. We find results compatible with lattice QCD data, as well as with functional methods applied in different gauges. The phase transition is of the expected order and we computed critical exponents. Extensions of the model are discussed. When investigating the QCD phase diagram, we compute the effects of dynamical quarks at finite density on the running of the gauge coupling. Additionally, we calculate how these affect the deconfinement phase transition, also, dynamical quarks allow for the inclusion of a finite chemical potential. Concluding the investigation of the phase diagram, we establish a relation between confinement and chiral symmetry breaking, which is tied to the dynamical generation of hadron masses. In the investigations, we often encounter scale dependent fields. We investigate a footing on which these can be dealt with in a uniform way. (orig.)
Chiral symmetry in light-front QCD
Wu, Menh-Hsiu; Zhang, Wei-Min
The definition of chiral transformations in light-front field theory is very different from the conventional form in equal-time formalism. We study the consistency of chiral transformations and chiral symmetry in light-front QCD and derive a complete new light-front axial-vector current for QCD. The breaking of chiral symmetry in light-front QCD is only associated with helicity flip interaction between quarks and gluons. Remarkably, the new axial-vector current does not contain the pion pole part so that the associate chiral charge smoothly describes pion transitions for various hadronic processes.
Chiral Symmetry in Light-front QCD
Wu, Meng-Hsiu; Zhang, Wei-Min
The definition of chiral transformations in light-front field theory is very different from the conventional form in equal-time formalism. We study the consistency of chiral transformations and chiral symmetry in light-front QCD and derive a complete new light-front axial-vector current for QCD. The breaking of chiral symmetry in light-front QCD is only associated with helicity flip interaction between quarks and gluons. Remarkably, the new axial-vector current does not contain the pion pole ...
Polyakov loop modeling for hot QCD
Fukushima, Kenji; Skokov, Vladimir
We review theoretical aspects of quantum chromodynamics (QCD) at finite temperature. The most important physical variable to characterize hot QCD is the Polyakov loop, which is an approximate order parameter for quark deconfinement in a hot gluonic medium. Additionally to its role as an order parameter, the Polyakov loop has rich physical contents in both perturbative and non-perturbative sectors. This review covers a wide range of subjects associated with the Polyakov loop from topological defects in hot QCD to model building with coupling to the Polyakov loop.
Death to perturbative QCD in exclusive processes?
Energy Technology Data Exchange (ETDEWEB)
Eckardt, R.; Hansper, J.; Gari, M.F. [Institut fuer Theoretische Physik, Bochum (Germany)
The authors discuss the question of whether perturbative QCD is applicable in calculations of exclusive processes at available momentum transfers. They show that the currently used method of determining hadronic quark distribution amplitudes from QCD sum rules yields wave functions which are completely undetermined because the polynomial expansion diverges. Because of the indeterminacy of the wave functions no statement can be made at present as to whether perturbative QCD is valid. The authors emphasize the necessity of a rigorous discussion of the subject and the importance of experimental data in the range of interest.
CERN. Geneva
The LHC energy regime poses a serious challenge to our capability of predicting QCD reactions to the level of accuracy necessary for a successful programme of searches for physics beyond the Standard Model. In these lectures, I'll introduce basic concepts in QCD, and present techniques based on perturbation theory, such as fixed-order and resummed computations, and Monte Carlo simulations. I'll discuss applications of these techniques to hadron-hadron processes, concentrating on recent trends in perturbative QCD aimed at improving our understanding of LHC phenomenology.
Light-Front Holography and Non-Perturbative QCD
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC; de Teramond, Guy F.; /Costa Rica U.
The combination of Anti-de Sitter space (AdS) methods with light-front holography leads to a semi-classical first approximation to the spectrum and wavefunctions of meson and baryon light-quark bound states. Starting from the bound-state Hamiltonian equation of motion in QCD, we derive relativistic light-front wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. These equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-J modes in anti-de Sitter (AdS) space. Its eigenvalues give the hadronic spectrum, and its eigenmodes represent the probability distribution of the hadronic constituents at a given scale. Applications to the light meson and baryon spectra are presented. The predicted meson spectrum has a string-theory Regge form M{sup 2} = 4{kappa}{sup 2}(n + L + S = 2); i.e., the square of the eigenmass is linear in both L and n, where n counts the number of nodes of the wavefunction in the radial variable {zeta}. The space-like pion form factor is also well reproduced. One thus obtains a remarkable connection between the description of hadronic modes in AdS space and the Hamiltonian formulation of QCD in physical space-time quantized on the light-front at fixed light-front time {tau}. The model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms.
Pion structure from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Javadi Motaghi, Narjes
In this thesis we use lattice QCD to compute the second Mellin moments of pion generalized parton distributions and pion electromagnetic form factors. For our calculations we are able to analyze a large set of gauge configurations with 2 dynamical flavours using non-perturbatively the improved Wilson-Sheikholeslami-Wohlert fermionic action pion masses ranging down to 151 MeV. By employing improved smearing we were able to suppress excited state contamination. However, our data in the physical quark mass limit show that some excited state contamination remains. We show the non-zero sink momentum is optimal for the computation of the electromagnetic form factors and generalized form factors at finite momenta.
Exclusive diffractive processes in QCD
Pichowsky, M. A.; Lee, T.-S. H.
We consider the role of nonperturbative, confined quarks in the Pomeron-exchange model of exclusive, diffractive processes. In our approach, mesons are treated as q-barq bound states and Pomeron-exchange mediates the quark-nucleon interaction. This interaction is modeled in terms of 4 parameters which are completely determined by examining π p and K p elastic scattering. The predicted ρ- and φ-meson electroproduction cross sections are in excellent agreement with the data. It is shown that the differences in the behavior of electroproduction cross sections for the different vector mesons (ρ, φ, J/ψ) arise from their quark substructures. Furthermore, several interesting features of vector meson electroproduction, recently observed at DESY, naturally arise in this approach. The model is also used to predict ρ p, φ p, ρ ρ, φ φ, and φ ρ elastic scattering cross sections necessary for investigations of QCD aspects of vector meson production from relativistic heavy ion collisions.
Soft Pomeron in Holographic QCD
Ballon-Bayona, Alfonso; Costa, Miguel S; Djurić, Marko
We study the graviton Regge trajectory in Holographic QCD as a model for high energy scattering processes dominated by soft pomeron exchange. This is done by considering spin J fields from the closed string sector that are dual to glueball states of even spin and parity. In particular, we construct a model that governs the analytic continuation of the spin J field equation to the region of real J < 2, which includes the scattering domain of negative Maldelstam variable t. The model leads to approximately linear Regge trajectories and is compatible with the measured values of 1.08 for the intercept and 0.25 GeV$^{-2}$ for the slope of the soft pomeron. The intercept of the secondary pomeron trajectory is in the same region of the subleading trajectories, made of mesons, proposed by Donnachie and Landshoff, and should therefore be taken into account.
Shear Viscosity from Lattice QCD
Mages, Simon W; Fodor, Zoltán; Schäfer, Andreas; Szabó, Kálmán
Understanding of the transport properties of the the quark-gluon plasma is becoming increasingly important to describe current measurements at heavy ion collisions. This work reports on recent efforts to determine the shear viscosity h in the deconfined phase from lattice QCD. The main focus is on the integration of the Wilson flow in the analysis to get a better handle on the infrared behaviour of the spectral function which is relevant for transport. It is carried out at finite Wilson flow time, which eliminates the dependence on the lattice spacing. Eventually, a new continuum limit has to be carried out which sends the new regulator introduced by finite flow time to zero. Also the non-perturbative renormalization strategy applied for the energy momentum tensor is discussed. At the end some quenched results for temperatures up to 4 : 5 T c are presented
Iancu, Edmond
These lectures provide a modern introduction to selected topics in the physics of ultrarelativistic heavy ion collisions which shed light on the fundamental theory of strong interactions, the Quantum Chromodynamics. The emphasis is on the partonic forms of QCD matter which exist in the early and intermediate stages of a collision -- the colour glass condensate, the glasma, and the quark-gluon plasma -- and on the effective theories that are used for their description. These theories provide qualitative and even quantitative insight into a wealth of remarkable phenomena observed in nucleus-nucleus or deuteron-nucleus collisions at RHIC and/or the LHC, like the suppression of particle production and of azimuthal correlations at forward rapidities, the energy and centrality dependence of the multiplicities, the ridge effect, the limiting fragmentation, the jet quenching, or the dijet asymmetry.
Lattice QCD for nuclear physics
Meyer, Harvey
With ever increasing computational resources and improvements in algorithms, new opportunities are emerging for lattice gauge theory to address key questions in strongly interacting systems, such as nuclear matter. Calculations today use dynamical gauge-field ensembles with degenerate light up/down quarks and the strange quark and it is possible now to consider including charm-quark degrees of freedom in the QCD vacuum. Pion masses and other sources of systematic error, such as finite-volume and discretization effects, are beginning to be quantified systematically. Altogether, an era of precision calculation has begun, and many new observables will be calculated at the new computational facilities. The aim of this set of lectures is to provide graduate students with a grounding in the application of lattice gauge theory methods to strongly interacting systems, and in particular to nuclear physics. A wide variety of topics are covered, including continuum field theory, lattice discretizations, hadron spect...
NLO dispersion laws for slow-moving quarks in HTL QCD
Energy Technology Data Exchange (ETDEWEB)
Abada, Abdessamad [Laboratoire de Physique des Particules et Physique Statistique, Ecole Normale Supérieure,BP 92 Vieux Kouba, 16050 Alger (Algeria); Physics Department, United Arab Emirates University,POB 17551 Al Ain (United Arab Emirates); Benchallal, Karima; Bouakaz, Karima [Laboratoire de Physique des Particules et Physique Statistique, Ecole Normale Supérieure,BP 92 Vieux Kouba, 16050 Alger (Algeria)
We determine the next-to-leading order dispersion laws for slow-moving quarks in hard-thermal-loop perturbation of high-temperature QCD where weak coupling is assumed. Real-time formalism is used. The next-to-leading order quark self-energy is written in terms of three and four HTL-dressed vertex functions. The hard thermal loops contributing to these vertex functions are calculated ab initio and expressed using the Feynman parametrization which allows the calculation of the solid-angle integrals involved. We use a prototype of the resulting integrals to indicate how finite results are obtained in the limit of vanishing regularizer.
Evolved QCD predictions for the meson-photon transition form factors: beyond the semiclassical AdS/QCD approximation
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC; Cao, Fu-Guang; /Massey U. /Beijing Normal U.; de Teramond, Guy F.; /Costa Rica U.
The QCD evolution of the pion distribution amplitude (DA) {phi}{sub {pi}} (x, Q{sup 2}) is computed for several commonly used models. Our analysis includes the nonperturbative form predicted by lightfront holographic QCD, thus combining the nonperturbative bound state dynamics of the pion with the perturbative ERBL evolution of the pion distribution amplitude. We calculate the meson-photon transition form factors for the {pi}{sup 0}, {eta} and {eta}' using the hard-scattering formalism. We point out that a widely-used approximation of replacing {phi} (x; (1 - x)Q) with {phi} (x;Q) in the calculations will unjustifiably reduce the predictions for the meson-photon transition form factors. It is found that the four models of the pion DA discussed give very different predictions for the Q{sup 2} dependence of the meson-photon transition form factors in the region of Q{sup 2} > 30 GeV{sup 2}. More accurate measurements of these transition form factors at the large Q{sup 2} region will be able to distinguish the four models of the pion DA. The rapid growth of the large Q{sup 2} data for the pion-photon transition form factor reported by the BABAR Collaboration is difficult to explain within the current framework of QCD. If the BABAR data for the meson-photon transition form factor for the {pi}{sup 0} is confirmed, it could indicate physics beyond-the-standard model, such as a weakly-coupled elementary C = + axial vector or pseudoscalar z{sup 0} in the few GeV domain, an elementary field which would provide the coupling {gamma}{sup *}{gamma} {yields} z{sup 0} {yields} {pi}{sup 0} at leading twist. Our analysis thus indicates the importance of additional measurements of the pion-photon transition form factor at large Q{sup 2}.
Soft QCD at the CMS and ATLAS experiments
Veres, Gabor
A short overview of some of the recent results on soft QCD processes at the LHC will be presented from the ATLAS and CMS experiments. The discussion will proceed starting from the most inclusive to the more differential and rare phenomena. New results include total inelastic cross section measurements; studies of minimum bias collisions (charged particle $\\eta$ and $p_T$ distributions and two-particle correlations in high-multiplicity events); features of the underlying event (multiplicity and $\\Sigma p_T$ distributions in the presence of a high-$p_T$ track, jet, Z boson or $t\\overline{t}$ pair); minijets characterizing the transition between the soft and hard QCD regimes; dijets with a rapidity gap (as a signature of color-singlet exchange); M\\uller-Navelet dijets and their angular decorrelations (as an attempt to search for signs of the BFKL evolution and deviations from DGLAP); and finally, Double Parton Scattering (DPS) studies using various final states (4-jet events, $\\gamma$ + 3 jets, 2 b-jets and 2 je...
From hot lattice QCD to cold quark stars
Energy Technology Data Exchange (ETDEWEB)
Schulze, Robert
A thermodynamic model of the quark-gluon plasma using quasiparticle degrees of freedom based on the hard thermal loop self-energies is introduced. It provides a connection between an established phenomenological quasiparticle model - following from the former using a series of approximations - and QCD - from which the former is derived using the Cornwall-Jackiw-Tomboulis formalism and a special parametrization of the running coupling. Both models allow for an extrapolation of first-principle QCD results available at small chemical potentials using Monte-Carlo methods on the lattice to large net baryon densities with remarkably similar results. They are used to construct equations of state for heavy-ion collider experiments at SPS and FAIR as well as quark and neutron star interiors. A mixed-phase construction allows for a connection of the SPS equation of state to the hadron resonance gas. An extension to the weak sector is presented as well as general stability and binding arguments for compact stellar objects are developed. From the extrapolation of the most recent lattice results the existence of bound pure quark stars is not suggested. However, quark matter might exist in a hybrid phase in cores of neutron stars. (orig.)
Standard hardness conversion tables for metals relationship among brinell hardness, vickers hardness, rockwell hardness, superficial hardness, knoop hardness, and scleroscope hardness
American Society for Testing and Materials. Philadelphia
1.1 Conversion Table 1 presents data in the Rockwell C hardness range on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, Knoop hardness, and Scleroscope hardness of non-austenitic steels including carbon, alloy, and tool steels in the as-forged, annealed, normalized, and quenched and tempered conditions provided that they are homogeneous. 1.2 Conversion Table 2 presents data in the Rockwell B hardness range on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, Knoop hardness, and Scleroscope hardness of non-austenitic steels including carbon, alloy, and tool steels in the as-forged, annealed, normalized, and quenched and tempered conditions provided that they are homogeneous. 1.3 Conversion Table 3 presents data on the relationship among Brinell hardness, Vickers hardness, Rockwell hardness, Rockwell superficial hardness, and Knoop hardness of nickel and high-nickel alloys (nickel content o...
Boring of full scale deposition holes at the Aespoe Hard Rock Laboratory. Operational experiences including boring performance and a work time analysis
Energy Technology Data Exchange (ETDEWEB)
Andersson, Christer [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden); Johansson, Aasa [SWECO, Stockholm (Sweden)
Thirteen experimental deposition holes similar to those in the present KBS-3 design have been bored at the Aespoe Hard Rock Laboratory, Oskarshamn, Sweden. The objective with the boring program was to test and demonstrate the current technique for boring of large vertical holes in granitic rock. Conclusions and results from this project is used in the planning process for the deposition holes that will be bored in the real repository for spent nuclear fuel. The boreholes are also important for three major projects. The Prototype Repository, the Canister Retrieval Test and the Demonstration project will all need full-scale deposition holes for their commissioning. The holes are bored in full scale and have a radius of 1.75 m and a depth of 8.5 m. To bore the holes an existing TBM design was modified to produce a novel type Shaft Boring Machine (SBM) suitable for boring 1.75 m diameter holes from a relatively small tunnel. The cutter head was equipped with two types of roller cutters: two row carbide button cutters and disc cutters. Removal of the cuttings was made with a vacuum suction system. The boring was monitored and boring parameters recorded by a computerised system for the evaluation of the boring performance. During boring of four of the holes temperature, stress and strain measurements were performed. Acoustic emission measurements were also performed during boring of these four holes. The results of these activities will not be discussed in this report since they are reported separately. Criteria regarding nominal borehole diameter, deviation of start and end centre point, surface roughness and performance of the machine were set up according to the KBS-3 design and were fulfilled with a fair margin. The average total time for boring one deposition hole during this project was 105 hours.
Chiral perturbation theory for lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Baer, Oliver
The formulation of chiral perturbation theory (ChPT) for lattice Quantum Chromodynamics (QCD) is reviewed. We start with brief summaries of ChPT for continuum QCD as well as the Symanzik effective theory for lattice QCD. We then review the formulation of ChPT for lattice QCD. After an additional chapter on partial quenching and mixed action theories various concrete applications are discussed: Wilson ChPT, staggered ChPT and Wilson ChPT with a twisted mass term. The remaining chapters deal with the epsilon regime with Wilson fermions and selected results in mixed action ChPT. Finally, the formulation of heavy vector meson ChPT with Wilson fermions is discussed. (orig.)
Mariani, Valentina
An overview of the Soft QCD latest measurements will be shown. The results from both the experiments ATLAS and CMS will be compared to each other and the agreement between data and Monte Carlo models will be discussed.
Review of Baryon Spectroscopy in Lattice QCD
Lin, Huey-Wen
The complex patterns of the hadronic spectrum have puzzled physicists since the early discovery of the "particle zoo" in the 1960s. Today, the properties of these myriad particles are understood to be the result of quantum chromodynamics (QCD) with some modification by the electroweak interactions. Despite the discovery of this fundamental theory, the description of the hadronic spectrum has long been dominated by phenomenological models, due to the difficulties of addressing QCD in the strong-coupling regime, where nonperturbative effects are essential. By making numerical calculations in discretized spacetime, lattice gauge theory enables the ab initio study of many low-energy properties of QCD. Significant efforts are underway internationally to use lattice QCD to directly compute properties of ground and excited-state baryons. Detailed knowledge of the hadronic spectrum will provide insight into the character of these states beyond what can be extracted from models. In this review, I will focus on the lat...
Some New/Old Approaches to QCD
Gross, D. J.
In this lecture I shall discuss some recent attempts to revive some old ideas to address the problem of solving QCD. I believe that it is timely to return to this problem which has been woefully neglected for the last decade. QCD is a permanent part of the theoretical landscape and eventually we will have to develop analytic tools for dealing with the theory in the infra-red. Lattice techniques are useful but they have not yet lived up to their promise. Even if one manages to derive the hadronic spectrum numerically, to an accuracy of 10% or even 1%, we will not be truly satisfied unless we have some analytic understanding of the results. Also, lattice Monte-Carlo methods can only be used to answer a small set of questions. Many issues of great conceptual and practical interest-in particular the calculation of scattering amplitudes, are thus far beyond lattice control. Any progress in controlling QCD in an explicit analytic, fashion would be of great conceptual value. It would also be of great practical aid to experimentalists, who must use rather ad-hoc and primitive models of QCD scattering amplitudes to estimate the backgrounds to interesting new physics. I will discuss an attempt to derive a string representation of QCD and a revival of the large N approach to QCD. Both of these ideas have a long history, many theorist-years have been devoted to their pursuit-so far with little success. I believe that it is time to try again. In part this is because of the progress in the last few years in string theory. Our increased understanding of string theory should make the attempt to discover a stringy representation of QCD easier, and the methods explored in matrix models might be employed to study the large N limit of QCD.
Lattice QCD and the Jefferson Laboratory Program
Energy Technology Data Exchange (ETDEWEB)
Jozef Dudek, Robert Edwards, David Richards, Konstantinos Orginos
Lattice gauge theory provides our only means of performing \\textit{ab initio} calculations in the non-perturbative regime. It has thus become an increasing important component of the Jefferson Laboratory physics program. In this paper, we describe the contributions of lattice QCD to our understanding of hadronic and nuclear physics, focusing on the structure of hadrons, the calculation of the spectrum and properties of resonances, and finally on deriving an understanding of the QCD origin of nuclear forces.
Recent QCD Studies at the Tevatron
Energy Technology Data Exchange (ETDEWEB)
Group, Robert Craig
Since the beginning of Run II at the Fermilab Tevatron the QCD physics groups of the CDF and D0 experiments have worked to reach unprecedented levels of precision for many QCD observables. Thanks to the large dataset--over 3 fb{sup -1} of integrated luminosity recorded by each experiment--important new measurements have recently been made public and will be summarized in this paper.
Finite Temperature Qcd With Domain Wall Fermions
Fleming, G T
Domain wall fermions are a new lattice fermion formulation which preserves the full chiral symmetry of the continuum at finite lattice spacing, up to terms exponentially small in an extra parameter. We discuss the main features of the formulation and its application to study of QCD with two light fermions of equal mass. We also present numerical studies of the two flavor QCD thermodynamics with aT = 1/4.
Understanding Theoretical Uncertainties in Perturbative QCD Computations
DEFF Research Database (Denmark)
Jenniches, Laura Katharina
effective field theories and perturbative QCD to predict the effect of New Physics on measurements at the LHC and at other future colliders. We use heavy-quark, heavy-scalar and soft-collinear effective theory to calculate a three-body cascade decay at NLO QCD in the expansion-by-regions formalism...... discuss an extension of the Cacciari-Houdeau approach to observables with hadrons in the initial state....
QCD evolution of the gluon density in a nucleus
Energy Technology Data Exchange (ETDEWEB)
Ayala Filho, A.L. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica]|[Universidade Federal de Pelotas, RS (Brazil). Inst. de Fisica e Matematica; Ducati, M.B. Gay [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica; Levin, E.M. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]|[Petersburg Nuclear Physics Inst., St. Petersburg (Russian Federation). Theory Dept.
The Glauber approach to the gluon density in a nucleus, suggested by A. Mueller, is developed and studied in detail. Using the GRV parameterization for the gluon density in a nucleon, the value as well as energy and Q{sup 2} dependence of the gluon density in a nucleus is calculated. It is shown that the shadowing corrections are under theoretical control and are essential in the region of small x. The change crucially the value of the gluon density as well as the value of the anomalous dimension of the nuclear structure function, unlike of the nucleon one. The systematic theoretical way to treat the correction to the Glauber approach is developed and a new evolution equation is derived and solved. It is shown that the solution of the new evolution equation can provide a self consistent matching of `soft` high energy phenomenology with `hard` QCD physics. (author). 51 refs., 25 figs., 1 tab.
Drell-Yan diffraction: breakdown of QCD factorization
Energy Technology Data Exchange (ETDEWEB)
Pasechnik, R.S. [Lund University, Theoretical High Energy Physics, Department of Astronomy and Theoretical Physics, Lund (Sweden); Kopeliovich, B.Z. [Universidad Tecnica Federico Santa Maria, Departamento de Fisica, Valparaiso (Chile); Instituto de Estudios Avanzados en Ciencias e Ingenieria, Valparaiso (Chile); Centro Cientifico-Tecnologico de Valparaiso, Valparaiso (Chile)
We consider the diffractive Drell-Yan process in proton-(anti)proton collisions at high energies in the color dipole approach. The calculations are performed at forward rapidities of the leptonic pair. The effect of eikonalization of the universal ''bare'' dipole-target elastic amplitude in the saturation regime takes into account the principal part of the gap survival probability. We present predictions for the total and differential cross sections of the single-diffractive lepton-pair production at RHIC and LHC energies. We analyze implications of the QCD factorization breakdown in the diffractive Drell-Yan process, which is caused by a specific interplay of the soft and hard interactions, resulting in rather unusual properties of the corresponding observables. (orig.)
Jet formation and interference in a thin QCD medium
Casalderrey-Solana, Jorge; Tywoniuk, Konrad
In heavy-ion collisions, an abundant production of high-energy QCD jets allows to study how these multiparticle sprays are modified as they pass through the quark-gluon plasma. In order to shed new light on this process, we compute the inclusive two-gluon rate off a hard quark propagating through a color deconfined medium at first order in medium opacity. We explicitly impose an energy ordering of the two emitted gluons, such that the "hard" gluon can be thought of as belonging to the jet substructure while the other is a "soft" emission (which can be collinear or medium-induced). Our analysis focusses on two specific limits that clarify the modification of the additional angle- and formation time-ordering of splittings. In one limit, the formation time of the "hard" gluon is short compared to the "soft" gluon formation time, leading to a probabilistic formula for production of and subsequent radiation off a quark-gluon antenna. In the other limit, the ordering of formation is reverted, which automatically le...
NLO QCD and electroweak corrections to Wγ and Zγ production
Energy Technology Data Exchange (ETDEWEB)
Hecht, Markus
In this thesis we investigate the production of a massive weak vector boson W{sup ±} or Z in association with a photon, where the vector boson decays leptonically. This type of processes is particularly interesting, since it allows to test the non-Abelian couplings of the EW gauge bosons. Furthermore, the channel pp→Zγ→l{sup +}l{sup -}γ is the main background to the Higgs-decay channel pp→h→Zγ, and Vγ (V=W,Z) production is an important background for various new-physics searches. In this thesis we present the calculation of the full NLO QCD+EW corrections. Therefore, we first reproduce the well known NLO QCD corrections. The EW corrections are calculated including the decay of the massive vector boson and taking into account all off-shell effects. The finite widths of the W and the Z boson are implemented by using the complex-mass scheme. Contributions from photon-induced channels are also taken into account applying up-to-date photon PDFs. Considering the fact that electrons and muons have different signatures in the detectors we present results for dressed leptons and bare muons. Calculating NLO corrections infra red divergences appear during the numerical integration of the real corrections. These divergences cancel against their counterparts in the virtual corrections as dictated by the KLN theorem. In order to extract the infra red divergences from the real corrections, we apply a so-called dipole subtraction algorithm allowing for a proper numerical integration of the real corrections. Separating hard photons from collinear jets, a quark-to-photon fragmentation function in combination with so-called democratic clustering 'a la Glover and Morgan is employed. As an alternative we also apply Frixione's isolation scheme. Finally, anomalous ZγV (V=W,Z) and WWγ couplings are implemented at the level of NLO QCD. We present integrated cross sections for the LHC at 7 TeV, 8 TeV, and 14 TeV. Furthermore, we show differential distributions at 14
Domain wall QCD with physical quark masses
Blum, T.; Christ, N.H.; Frison, J.; Garron, N.; Hudspith, R.J.; Izubuchi, T.; Janowski, T.; Jung, C.; Jüttner, A.; Kelly, C.; Kenway, R.D.; Lehner, C.; Marinkovic, M.; Mawhinney, R.D.; McGlynn, G.; Murphy, D.J.; Ohta, S.; Portelli, A.; Sachrajda, C.T.; Soni, A.
We present results for several light hadronic quantities ($f_\\pi$, $f_K$, $B_K$, $m_{ud}$, $m_s$, $t_0^{1/2}$, $w_0$) obtained from simulations of 2+1 flavor domain wall lattice QCD with large physical volumes and nearly-physical pion masses at two lattice spacings. We perform a short, O(3)%, extrapolation in pion mass to the physical values by combining our new data in a simultaneous chiral/continuum `global fit' with a number of other ensembles with heavier pion masses. We use the physical values of $m_\\pi$, $m_K$ and $m_\\Omega$ to determine the two quark masses and the scale - all other quantities are outputs from our simulations. We obtain results with sub-percent statistical errors and negligible chiral and finite-volume systematics for these light hadronic quantities, including: $f_\\pi$ = 130.2(9) MeV; $f_K$ = 155.5(8) MeV; the average up/down quark mass and strange quark mass in the $\\bar {\\rm MS}$ scheme at 3 GeV, 2.997(49) and 81.64(1.17) MeV respectively; and the neutral kaon mixing parameter, $B_K$...
Hard exclusive pseudoscalar meson electroproduction and spin structure of the nucleon
Frankfurt, L. L.; Pobylitsa, P. V.; Polyakov, M. V.; Strikman, M.
The amplitude for hard exclusive pseudoscalar meson electroproduction off nucleon (nuclear) targets is computed in QCD within the leading αslnQ2/Λ2QCD approximation. We show that the distribution of recoil nucleons depends strongly on the angle between the momentum of the recoil nucleon and the polarization vector of the target (or outgoing nucleon). This dependence is especially sensitive to the spin flip skewed parton distribution (SPD) E~. We argue also that the scaling for this spin asymmetry sets in at lower Q2 than that for the absolute cross section. Based on the chiral quark-soliton model of the nucleon we estimate quantitatively the spin asymmetry. In the case of π+ production this asymmetry is dominated at small t by the contribution of the pion pole in the isovector SPD E~ as required by PCAC. In the case of K0 production off a proton we find a large enhancement of the cross section as compared to the case of π0 production. For the forward production of neutral pseudoscalar mesons off a deuteron target we find the cross section should be zero for the zero deuteron helicity (along the γ*D direction). We consider also cross sections of quasielastic processes off nuclei including the feasibility to implant K+,ρ mesons into nuclear volume.
Diluting the inflationary axion fluctuation by a stronger QCD in the early Universe
Directory of Open Access Journals (Sweden)
Kiwoon Choi
Full Text Available We propose a new mechanism to suppress the axion isocurvature perturbation, while producing the right amount of axion dark matter, within the framework of supersymmetric axion models with the axion scale induced by supersymmetry breaking. The mechanism involves an intermediate phase transition to generate the Higgs μ-parameter, before which the weak scale is comparable to the axion scale and the resulting stronger QCD yields an axion mass heavier than the Hubble scale over a certain period. Combined with that the Hubble-induced axion scale during the primordial inflation is well above the intermediate axion scale at present, the stronger QCD in the early Universe suppresses the axion fluctuation to be small enough even when the inflationary Hubble scale saturates the current upper bound, while generating an axion misalignment angle of order unity.
Critical slowing down and error analysis in lattice QCD simulations
Energy Technology Data Exchange (ETDEWEB)
Virotta, Francesco
In this work we investigate the critical slowing down of lattice QCD simulations. We perform a preliminary study in the quenched approximation where we find that our estimate of the exponential auto-correlation time scales as {tau}{sub exp}(a){proportional_to}a{sup -5}, where a is the lattice spacing. In unquenched simulations with O(a) improved Wilson fermions we do not obtain a scaling law but find results compatible with the behavior that we find in the pure gauge theory. The discussion is supported by a large set of ensembles both in pure gauge and in the theory with two degenerate sea quarks. We have moreover investigated the effect of slow algorithmic modes in the error analysis of the expectation value of typical lattice QCD observables (hadronic matrix elements and masses). In the context of simulations affected by slow modes we propose and test a method to obtain reliable estimates of statistical errors. The method is supposed to help in the typical algorithmic setup of lattice QCD, namely when the total statistics collected is of O(10){tau}{sub exp}. This is the typical case when simulating close to the continuum limit where the computational costs for producing two independent data points can be extremely large. We finally discuss the scale setting in N{sub f}=2 simulations using the Kaon decay constant f{sub K} as physical input. The method is explained together with a thorough discussion of the error analysis employed. A description of the publicly available code used for the error analysis is included.
Five-Loop Running of the QCD Coupling Constant.
Baikov, P A; Chetyrkin, K G; Kühn, J H
We analytically compute the five-loop term in the beta function which governs the running of α_{s}-the quark-gluon coupling constant in QCD. The new term leads to a reduction of the theory uncertainty in α_{s} taken at the Z-boson scale as extracted from the τ-lepton decays as well as to new, improved by one more order of perturbation theory, predictions for the effective coupling constants of the standard model Higgs boson to gluons and for its total decay rate to the quark-antiquark pairs.
Hadronic and nuclear interactions in QCD
Energy Technology Data Exchange (ETDEWEB)
Despite the evidence that QCD - or something close to it - gives a correct description of the structure of hadrons and their interactions, it seems paradoxical that the theory has thus far had very little impact in nuclear physics. One reason for this is that the application of QCD to distances larger than 1 fm involves coherent, non-perturbative dynamics which is beyond present calculational techniques. For example, in QCD the nuclear force can evidently be ascribed to quark interchange and gluon exchange processes. These, however, are as complicated to analyze from a fundamental point of view as is the analogous covalent bond in molecular physics. Since a detailed description of quark-quark interactions and the structure of hadronic wavefunctions is not yet well-understood in QCD, it is evident that a quantitative first-principle description of the nuclear force will require a great deal of theoretical effort. Another reason for the limited impact of QCD in nuclear physics has been the conventional assumption that nuclear interactions can for the most part be analyzed in terms of an effective meson-nucleon field theory or potential model in isolation from the details of short distance quark and gluon structure of hadrons. These lectures, argue that this view is untenable: in fact, there is no correspondence principle which yields traditional nuclear physics as a rigorous large-distance or non-relativistic limit of QCD dynamics. On the other hand, the distinctions between standard nuclear physics dynamics and QCD at nuclear dimensions are extremely interesting and illuminating for both particle and nuclear physics.
NLO QCD corrections to Higgs boson production plus three jets in gluon fusion
Energy Technology Data Exchange (ETDEWEB)
Cullen, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Deurzen, H. van; Greiner, N.; Luisoni, G.; Mirabella, E.; Peraro, T. [Max-Planck-Institut fuer Physik, Muenchen (Germany); Mastrolia, P. [Max-Planck-Institut fuer Physik, Muenchen (Germany); Padova Univ. (Italy). Dipt. di Fisica e Astronomia; INFN, Sezione di Padova (Italy); Ossola, G. [New York Univ., NY (United States). New York City College of Technology; New York Univ., NY (United States). The Graduate School and University Center; Tramontano, F. [Napoli Univ. (Italy). Dipt. di Fisica; INFN, Sezione di Napoli (Italy)
We report on the calculation of the cross section for Higgs boson production in association with three jets via gluon fusion, at next-to-leading-order (NLO) accuracy in QCD, in the infinite top-mass approximation. After including the complete NLO QCD corrections, we observe a strong reduction in the scale dependence of the result, and an increased steepness in the transverse momentum distributions of both the Higgs and the leading jets. The results are obtained with the combined use of GoSam, Sherpa, and the MadDipole/MadEvent framework.
Two-particle angular correlations in $e^+ e^-$ interactions compared with QCD predictions
Abreu, P; Adye, T; Adzic, P; Ajinenko, I; Alekseev, G D; Alemany, R; Allport, P P; Almehed, S; Amaldi, Ugo; Amato, S; Anassontzis, E G; Andersson, P; Andreazza, A; Andringa, S; Antilogus, P; Apel, W D; Arnoud, Y; Åsman, B; Augustin, J E; Augustinus, A; Baillon, Paul; Bambade, P; Barão, F; Barbiellini, Guido; Barbier, R; Bardin, Dimitri Yuri; Barker, G; Baroncelli, A; Battaglia, Marco; Baubillier, M; Becks, K H; Begalli, M; Beillière, P; Belokopytov, Yu A; Belous, K S; Benvenuti, Alberto C; Bérat, C; Berggren, M; Bertini, D; Bertrand, D; Besançon, M; Bianchi, F; Bigi, M; Bilenky, S M; Bizouard, M A; Bloch, D; Blom, H M; Bonesini, M; Bonivento, W; Boonekamp, M; Booth, P S L; Borgland, A W; Borisov, G; Bosio, C; Botner, O; Boudinov, E; Bouquet, B; Bourdarios, C; Bowcock, T J V; Boyko, I; Bozovic, I; Bozzo, M; Branchini, P; Brenke, T; Brenner, R A; Brückman, P; Brunet, J M; Bugge, L; Buran, T; Burgsmüller, T; Buschbeck, Brigitte; Buschmann, P; Cabrera, S; Caccia, M; Calvi, M; Camacho-Rozas, A J; Camporesi, T; Canale, V; Carena, F; Carroll, L; Caso, Carlo; Castillo-Gimenez, M V; Cattai, A; Cavallo, F R; Cerruti, C; Chabaud, V; Charpentier, P; Chaussard, L; Checchia, P; Chelkov, G A; Chierici, R; Chliapnikov, P V; Chochula, P; Chorowicz, V; Chudoba, J; Collins, P; Colomer, M; Contri, R; Cortina, E; Cosme, G; Cossutti, F; Cowell, J H; Crawley, H B; Crennell, D J; Crosetti, G; Cuevas-Maestro, J; Czellar, S; Damgaard, G; Davenport, Martyn; Da Silva, W; Deghorain, A; Della Ricca, G; Delpierre, P A; Demaria, N; De Angelis, A; de Boer, Wim; De Brabandere, S; De Clercq, C; De Lotto, B; De Min, A; De Paula, L S; Dijkstra, H; Di Ciaccio, Lucia; Di Diodato, A; Dolbeau, J; Doroba, K; Dracos, M; Drees, J; Dris, M; Duperrin, A; Durand, J D; Ehret, R; Eigen, G; Ekelöf, T J C; Ekspong, Gösta; Ellert, M; Elsing, M; Engel, J P; Erzen, B; Espirito-Santo, M C; Falk, E; Fanourakis, G K; Fassouliotis, D; Fayot, J; Feindt, Michael; Ferrari, P; Ferrer, A; Ferrer-Ribas, E; Fichet, S; Firestone, A; Fischer, P A; Flagmeyer, U; Föth, H; Fokitis, E; Fontanelli, F; Franek, B J; Frodesen, A G; Frühwirth, R; Fulda-Quenzer, F; Fuster, J A; Galloni, A; Gamba, D; Gamblin, S; Gandelman, M; García, C; García, J; Gaspar, C; Gaspar, M; Gasparini, U; Gavillet, P; Gazis, E N; Gelé, D; Gerber, J P; Gerdyukov, L N; Ghodbane, N; Gil, I; Glege, F; Gokieli, R; Golob, B; Gonçalves, P; González-Caballero, I; Gopal, Gian P; Gorn, L; Górski, M; Guz, Yu; Gracco, Valerio; Grahl, J; Graziani, E; Green, C; Gris, P; Grzelak, K; Günther, M; Guy, J; Hahn, F; Hahn, S; Haider, S; Hallgren, A; Hamacher, K; Harris, F J; Hedberg, V; Heising, S; Hernández, J J; Herquet, P; Herr, H; Hessing, T L; Heuser, J M; Higón, E; Holmgren, S O; Holt, P J; Holthuizen, D J; Hoorelbeke, S; Houlden, M A; Hrubec, Josef; Huet, K; Hultqvist, K; Jackson, J N; Jacobsson, R; Jalocha, P; Janik, R; Jarlskog, C; Jarlskog, G; Jarry, P; Jean-Marie, B; Johansson, E K; Jönsson, P E; Joram, C; Juillot, P; Kapusta, F; Karafasoulis, K; Katsanevas, S; Katsoufis, E C; Keränen, R; Khomenko, B A; Khovanskii, N N; Kiiskinen, A P; King, B J; Kjaer, N J; Klapp, O; Klein, H; Kluit, P M; Knoblauch, D; Kokkinias, P; Koratzinos, M; Kostyukhin, V; Kourkoumelis, C; Kuznetsov, O; Krammer, Manfred; Kreuter, C; Krstic, J; Krumshtein, Z; Kubinec, P; Kucewicz, W; Kurvinen, K L; Lamsa, J; Lane, D W; Langefeld, P; Lapin, V; Laugier, J P; Lauhakangas, R; Leder, Gerhard; Ledroit, F; Lefébure, V; Leinonen, L; Leisos, A; Leitner, R; Lenzen, Georg; Lepeltier, V; Lesiak, T; Lethuillier, M; Libby, J; Liko, D; Lipniacka, A; Lippi, I; Lörstad, B; Loken, J G; Lopes, J H; López, J M; López-Fernandez, R; Loukas, D; Lutz, P; Lyons, L; MacNaughton, J N; Mahon, J R; Maio, A; Malek, A; Malmgren, T G M; Malychev, V; Mandl, F; Marco, J; Marco, R P; Maréchal, B; Margoni, M; Marin, J C; Mariotti, C; Markou, A; Martínez-Rivero, C; Martínez-Vidal, F; Martí i García, S; Mastroyiannopoulos, N; Matorras, F; Matteuzzi, C; Matthiae, Giorgio; Masik, J; Mazzucato, F; Mazzucato, M; McCubbin, M L; McKay, R; McNulty, R; McPherson, G; Meroni, C; Meyer, W T; Myagkov, A; Migliore, E; Mirabito, L; Mitaroff, Winfried A; Mjörnmark, U; Moa, T; Møller, R; Mönig, K; Monge, M R; Moreau, X; Morettini, P; Morton, G A; Müller, U; Münich, K; Mulders, M; Mulet-Marquis, C; Muresan, R; Murray, W J; Muryn, B; Myatt, Gerald; Myklebust, T; Naraghi, F; Navarria, Francesco Luigi; Navas, S; Nawrocki, K; Negri, P; Neufeld, N; Neumeister, N; Nicolaidou, R; Nielsen, B S; Nikolaenko, V; Nikolenko, M; Nomokonov, V P; Normand, Ainsley; Nygren, A; Obraztsov, V F; Olshevskii, A G; Onofre, A; Orava, Risto; Orazi, G; Österberg, K; Ouraou, A; Paganoni, M; Paiano, S; Pain, R; Paiva, R; Palacios, J; Palka, H; Papadopoulou, T D; Papageorgiou, K; Pape, L; Parkes, C; Parodi, F; Parzefall, U; Passeri, A; Passon, O; Pegoraro, M; Peralta, L; Pernicka, Manfred; Perrotta, A; Petridou, C; Petrolini, A; Phillips, H T; Piana, G; Pierre, F; Pimenta, M; Piotto, E; Podobnik, T; Pol, M E; Polok, G; Poropat, P; Pozdnyakov, V; Privitera, P; Pukhaeva, N; Pullia, Antonio; Radojicic, D; Ragazzi, S; Rahmani, H; Rakoczy, D; Rames, J; Ratoff, P N; Read, A L; Rebecchi, P; Redaelli, N G; Reid, D; Reinhardt, R; Renton, P B; Resvanis, L K; Richard, F; Rídky, J; Rinaudo, G; Røhne, O M; Romero, A; Ronchese, P; Rosenberg, E I; Rosinsky, P; Roudeau, Patrick; Rovelli, T; Ruhlmann-Kleider, V; Ruiz, A; Saarikko, H; Sacquin, Yu; Sadovskii, A; Sajot, G; Salt, J; Sampsonidis, D; Sannino, M; Schneider, H; Schwemling, P; Schwickerath, U; Schyns, M A E; Scuri, F; Seager, P; Sedykh, Yu; Segar, A M; Sekulin, R L; Shellard, R C; Sheridan, A; Siebel, M; Silvestre, R; Simard, L C; Simonetto, F; Sissakian, A N; Skaali, T B; Smadja, G; Smirnova, O G; Smith, G R; Sopczak, André; Sosnowski, R; Spassoff, Tz; Spiriti, E; Sponholz, P; Squarcia, S; Stampfer, D; Stanescu, C; Stanic, S; Stapnes, Steinar; Stevenson, K; Stocchi, A; Strauss, J; Strub, R; Stugu, B; Szczekowski, M; Szeptycka, M; Tabarelli de Fatis, T; Chikilev, O G; Tegenfeldt, F; Terranova, F; Thomas, J; Tilquin, A; Timmermans, J; Tkatchev, L G; Todorov, T; Todorova, S; Toet, D Z; Tomaradze, A G; Tomé, B; Tonazzo, A; Tortora, L; Tranströmer, G; Treille, D; Tristram, G; Troncon, C; Tsirou, A L; Turluer, M L; Tyapkin, I A; Tzamarias, S; Überschär, B; Ullaland, O; Uvarov, V; Valenti, G; Vallazza, E; van Apeldoorn, G W; van Dam, P; Van Eldik, J; Van Lysebetten, A; Van Vulpen, I B; Vassilopoulos, N; Vegni, G; Ventura, L; Venus, W A; Verbeure, F; Verlato, M; Vertogradov, L S; Verzi, V; Vilanova, D; Vitale, L; Vlasov, E; Vodopyanov, A S; Voulgaris, G; Vrba, V; Wahlen, H; Walck, C; Weiser, C; Wicke, D; Wickens, J H; Wilkinson, G R; Winter, M; Witek, M; Wolf, G; Yi, J; Yushchenko, O P; Zalewska-Bak, A; Zalewski, Piotr; Zavrtanik, D; Zevgolatakos, E; Zimin, N I; Zucchelli, G C; Zumerle, G
Two--particle angular correlations in jet cones have been measured in $e^+e^-$ annihilation into hadrons at LEP energies ($\\sqrt{s}=$ 91 and 183~GeV) and are compared with QCD predictions using the LPHD hypothesis. Two different functions have been tested. While the differentially normalized correlation function shows substantial deviations from the predictions, a globally normalized correlation function agrees well. The size of $\\alpha_S^{\\rm eff}$ (and other QCD parameters) and its running with the relevant angular scale, the validity of LPHD, and problems due to non--perturbative effects are discussed critically.
Search for QCD-instanton induced events in deep inelastic ep scattering at HERA
Abramowicz, H; Adamus, M; Adler, V; Aghuzumtsyan, G; Antonioli, P; Antonov, A; Arneodo, M; Bailey, D S; Bamberger, A; Barakbaev, A N; Barbagli, G; Barbi, M; Bari, G; Barreiro, F; Bartsch, D; Basile, M; Behrens, U; Bell, M; Bellagamba, L; Benen, A; Bertolin, A; Bhadra, S; Bloch, I; Bodmann, B; Bold, T; Boos, E G; Borras, K; Boscherini, D; Brock, I; Brook, N H; Brugnera, R; Brümmer, N; Bruni, A; Bruni, G; Bussey, P J; Butterworth, J M; Bylsma, B; Caldwell, A; Capua, M; Cara Romeo, G; Carli, T; Carlin, R; Catterall, C D; Chekanov, S; Chiochia, V; Chwastowski, J; Ciborowski, J; Ciesielski, R; Cifarelli, Luisa; Cindolo, F; Cloth, P; Cole, J E; Collins-Tooth, C; Contin, A; Cooper-Sarkar, A M; Coppola, N; Cormack, C; Corradi, M; Corriveau, F; Cottrell, A; D'Agostini, G; Dal Corso, F; Danilov, P; Dannheim, D; De Pasquale, S; Dementiev, R K; Derrick, M; Deshpande, Abhay A; Devenish, R C E; Dhawan, S; Dobur, D; Dolgoshein, B A; Doyle, A T; Drews, G; Durkin, L S; Dusini, S; Eisenberg, Y; Ermolov, P F; Eskreys, Andrzej; Ferrando, J; Ferrero, M I; Figiel, J; Filges, D; Foster, B; Foudas, C; Fourletov, S; Fourletova, J; Fricke, U; Fusayasu, T; Gabareen, A; Galas, A; Gallo, E; Garfagnini, A; Geiser, A; Genta, C; Gialas, I; Giusti, P; Gladilin, L K; Gladkov, D; Glasman, C; Gliga, S; Goers, S; Golubkov, Yu A; Goncalo, R; González, O; Göttlicher, P; Grabowska-Bold, I; Grijpink, S; Grzelak, G; Gutsche, O; Gwenlan, C; Haas, T; Hain, W; Hall-Wilton, R; Hamatsu, R; Hamilton, J; Hanlon, S; Hart, J C; Hartmann, H; Hartner, G; Heaphy, E A; Heath, G P; Helbich, M; Heusch, C A; Hilger, E; Hillert, S; Hirose, T; Hochman, D; Holm, U; Iacobucci, G; Iga, Y; Inuzuka, M; Irrgang, P; Jakob, P; Jones, T W; Kagawa, S; Kahle, B; Kaji, H; Kananov, S; Karstens, F; Kataoka, M; Katkov, I I; Kcira, D; Khein, L A; Kim, J Y; Kim, Y K; Kind, O; Kisielewska, D; Kitamura, S; Klimek, K; Koffeman, E; Kohno, T; Kooijman, P; Koop, T; Korzhav, I A; Kotanski, A; Kötz, U; Kowal, A M; Kowal, M; Kowalski, H; Kowalski, T; Krakauer, D; Kramberger, G; Kreisel, A; Krumnack, N; Kuze, M; Kuzmin, V A; Labarga, L; Labes, H; Lainesse, J; Lammers, S; Lee, J H; Lelas, D; Levchenko, B B; Levman, G M; Levy, A; Li, L; Lightwood, M S; Lim, H; Lim, I T; Limentani, S; Ling, T Y; Liu, X; Löhr, B; Lohrmann, E; Loizides, J H; Long, K R; Longhin, A; Lukina, O Yu; Luzniak, P; Maddox, E; Magill, S; Mankel, R; Margotti, A; Marini, G; Martin, J F; Mastroberardino, A; Matsuzawa, K; Mattingly, M C K; McCubbin, N A; Mellado, B; Melzer-Pellmann, I A; Menary, S R; Metlica, F; Meyer, U; Miglioranzi, S; Milite, M; Mirea, A; Monaco, V; Montanari, A; Mus, B; Nagano, K; Namsoo, T; Nania, R; Nguyen, C N; Nigro, A; Ning, Y; Notz, D; Nowak, R J; Nuncio-Quiroz, A E; Oh, B Y; Olkiewicz, K; Pac, M Y; Padhi, S; Paganis, S; Palmonari, F; Parenti, A; Park, I H; Patel, S; Paul, E; Pavel, N; Pawlak, J M; Pelfer, P G; Pellegrino, A; Pesci, A; Piotrzkowski, K; Plucinsky, P P; Pokrovskiy, N S; Polini, A; Posocco, M; Proskuryakov, A S; Przybycien, M B; Rautenberg, J; Raval, A; Reeder, D D; Ren, Z; Renner, R; Repond, J; Riveline, U; Karshon, M; Robins, S; Rosin, M; Rurua, L; Ruspa, M; Sacchi, R; Salehi, H; Sartorelli, G; Savin, A A; Saxon, D H; Schagen, S; Schioppa, M; Schlenstedt, S; Schleper, P; Schmidke, W B; Schneekloth, U; Sciulli, F; Shcheglova, L M; Skillicorn, I O; Slominski, W; Smith, W H; Soares, M; Solano, A; Son, D; Sosnovtsev, V V; Stairs, D G; Stanco, L; Standage, J; Stifutkin, A; Stoesslein, U; Stonjek, S; Stopa, P; Straub, P B; Suchkov, S; Susinno, G; Suszycki, L; Sutton, M R; Sztuk, J; Szuba, D; Szuba, J; Tandler, J; Tapper, A D; Targett-Adams, C; Tassi, E; Tawara, T; Terron, J; Tiecke, H G; Tokushuku, K; Tsurugai, T; Turcato, M; Tymieniecka, T; Ukleja, A; Ukleja, J; Vázquez, M; Velthuis, J J; Vlasov, N N; Voss, K C; Walczak, R; Walsh, R; Wang, M; Weber, A; Whitmore, J J; Wick, K; Wiggers, L; Wills, H H; Wing, M; Wolf, G; Yamada, S; Yamashita, T; Yamazaki, Y; Yoshida, R; Youngman, C; Zambrana, M; Zawiejski, L; Zeuner, W; Zhautykov, B O; Zichichi, A; Ziegler, A; Zotkin, S A; De Wolf, E; Del Peso, J
A search for QCD-instanton-induced events in deep inelastic ep scattering has been performed with the ZEUS detector at the HERA collider, using data corresponding to an integrated luminosity of 38 pb^{-1}. A kinematic range defined by cuts on the photon virtuality, Q^2 > 120 GeV^2, and on the Bjorken scaling variable, x > 10^{-3}, has been investigated. The QCD-instanton induced events were modelled by the Monte Carlo generator QCDINS. A background-independent, conservative 95% confidence level upper limit for the instanton cross section of 26 pb is obtained, to be compared with the theoretically expected value of 8.9 pb.
Energy Technology Data Exchange (ETDEWEB)
Schaefer, Stefan [DESY (Germany). Neumann Inst. for Computing
These configurations are currently in use in many on-going projects carried out by researchers throughout Europe. In particular this data will serve as an essential input into the computation of the coupling constant of QCD, where some of the simulations are still on-going. But also projects computing the masses of hadrons and investigating their structure are underway as well as activities in the physics of heavy quarks. As this initial project of gauge field generation has been successful, it is worthwhile to extend the currently available ensembles with further points in parameter space. These will allow to further study and control systematic effects like the ones introduced by the finite volume, the non-physical quark masses and the finite lattice spacing. In particular certain compromises have still been made in the region where pion masses and lattice spacing are both small. This is because physical pion masses require larger lattices to keep the effects of the finite volume under control. At light pion masses, a precise control of the continuum extrapolation is therefore difficult, but certainly a main goal of future simulations. To reach this goal, algorithmic developments as well as faster hardware will be needed.
Nuclear reactions from lattice QCD
Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.
One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, quantum chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three-nucleon (and higher) interactions in a consistent manner. Currently, lattice quantum chromodynamics (LQCD) provides the only reliable option for performing calculations of some of the low-energy hadronic observables. With the aim of bridging the gap between LQCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from LQCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.
Energy Technology Data Exchange (ETDEWEB)
Loan Mushtaq [International School, Jinan University, Huangpu Road West, Guangzhou 510632 (China)], E-mail: email@example.com; Luo Zhihuan [Department of Applied Physics, South China Agricultural University, Wushan Road, Guangzhou 510642 (China); Lam Yuyiu [Department of Physics, Jinan University, Huangpu Road West, Guangzhou 510632 (China)
We present a search for the possible I(J{sup P})=0(2{sup +}) tetraquark state with sss-bar s-bar quark content in quenched improved anisotropic lattice QCD. Using various local and non-local interpolating fields we determine the energies of ground-state and second ground state using variational method. The state is found to be consistent with two-particle scattering state, which is checked to exhibit the expected volume dependence of the spectral weights. In the physical limit, we obtain for the ground state, a mass of 2123(33)(58) MeV which is higher than the mass of experimentally observed f(2010). The lattice resonance signal obtained in the physical region does not support a localized J{sup P}=2{sup +} tetraquark state in the pion mass region of 300-800 MeV. We conclude that the 4q system in question appears as a two-particle scattering state in the quark mass region explored here.
Loan, Mushtaq; Lam, Yu Yiu
We present a search for the possible $I(J^{P})=0(2^{+})$ tetraquark state with $ss{\\bar s}{\\bar s}$ quark content in quenched improved anisotropic lattice QCD. Using various local and non-local interpolating fields we determine the energies of ground-state and second ground state using variational method. The state is found to be consistent with two-particle scattering state, which is checked to exhibit the expected volume dependence of the spectral weights. In the physical limit, we obtain for the ground state, a mass of $2123(33)(58)$ MeV which is higher than the mass of experimentally observed $f(2010)$. The lattice resonance signal obtained in the physical region does not support a localized $J^{P} =2^{+}$ tetraquark state in the pion mass region of $300 - 800$ MeV. We conclude that the $4q$ system in question appears as a two-particle scattering state in the quark mass region explored here.
Nuclear Physics from Lattice QCD: The Spectrum, Structure and Interactions of Hadrons
Energy Technology Data Exchange (ETDEWEB)
David Richards; Colin Morningstar; John Negele; Konstantinos Orginos; Martin Savage
The importance of lattice QCD to our understanding of the structure, spectroscopy, and interaction of hadrons is decribed. Recent accomplishments in each of these areas is outlined, and the opportunities emerging with increasing computational power are identified. Milestones at the 10 Tflops-years, 100 Tflops-years and Petaflops-years scales are presented.
Local coherence and deflation of the low quark modes in lattice QCD
Lüscher, Martin
The spontaneous breaking of chiral symmetry in QCD is known to be linked to a non-zero density of eigenvalues of the massless Dirac operator near the origin. Numerical studies of two-flavour QCD now suggest that the low quark modes are locally coherent to a certain extent. As a consequence, the modes can be simultaneously deflated, using local projectors, with a total computational effort proportional to the lattice volume (rather than its square). Deflation has potentially many uses in lattice QCD. The technique is here worked out for the case of quark propagator calculations, where large speed-up factors and a flat scaling behaviour with respect to the quark mass are achieved.
Applications of AdS/QCD and Light-Front Holography to Baryon Physics
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC; de Teramond, Guy F.; /Costa Rica U.
The correspondence between theories in anti-de Sitter space and field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD which has scale invariance at short distances and color confinement at large distances. These equations, for both mesons and baryons, give a very good representation of the observed hadronic spectrum, including a zero mass pion. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. The meson and baryon wavefunctions derived from light-front holography and AdS/QCD also have remarkable phenomenological features, including predictions for the electromagnetic form factors and decay constants. The approach can be systematically improved using light-front Hamiltonian methods. Some novel features of QCD for baryon physics are also discussed.
Basics of QCD for the LHC: pp → H + X as a case study
Maltoni, F
Quantum Chromo Dynamics (QCD) provides the theoretical framework for any study of TeV scale physics at LHC. Being familiar with the basic concepts and techniques of QCD is therefore a must for any high-energy physicist. In these notes we consider Higgs production via gluon fusion as an example on how accurate and flexible predictions can be obtained in perturbative QCD. We start by illustrating how to calculate the total cross section at the leading order (yet one loop) in the strong coupling $\\alpha$S and go through the details of the next-to-leading order calculation eventually highlighting the limitations of fixed-order predictions at the parton level. Finally, we briefly discuss how more exclusive (and practical) predictions can be obtained through matching/merging fixed-order results with parton showers.
Transport Processes in High Temperature QCD Plasmas
Hong, Juhee
The transport properties of high temperature QCD plasmas can be described by kinetic theory based on the Boltzmann equation. At a leading-log approximation, the Boltzmann equation is reformulated as a Fokker-Planck equation. First, we compute the spectral densities of Tµν and Jµ by perturbing the system with weak gravitational and electromagnetic fields. The spectral densities exhibit a smooth transition from free-streaming quasi-particles to hydrodynamics. This transition is analyzed with hydrodynamics and diffusion equation up to second order. We determine all of the first and second order transport coefficients which characterize the linear response in the hydrodynamic regime. Second, we simulate the wake of a heavy quark moving through the plasmas. At long distances, the energy density and flux distributions show sound waves and a diffusion wake. The kinetic theory calculations based on the Boltzmann equation at weak coupling are compared to the strong coupling results given by the AdS/CFT correspondence. By using the hard-thermal-loop effective theory, we determine the photon emission rate at next-to-leading order (NLO), i.e., at order g2mD /T. There are three mechanisms which contribute to the leading-order photon emission: (2 ↔ 2) elastic scatterings, (1 ↔ 2) collinear bremsstrahlung, and (1 ↔ 1) quark-photon conversion due to soft fermion exchange. At NLO, these three mechanisms are not completely independent. When the transverse momentum between quark and photon becomes soft, the Compton scattering with a soft gluon reduces to wide-angle bremsstrahlung. Similarly, bremsstrahlung reduces to the quark-photon conversion process when the photon carries most of the incoming momentum. Therefore, the rates should be matched to determine the wide-angle NLO correction. Collinear bremsstrahlung can be accounted for by solving an integral equation which corresponds to summing ladder diagrams. With O(g) corrections in the collision kernel and the asymptotic
Thriving reefs in the Baltic? Diversity and small-scale variability of hard-bottom assemblages along natural and anthropogenic gradients in the German Baltic Sea
Beisiegel, K.; Zettler, M. L.; Darr, A.; Schiele, K.; Schwarzer, K.; Richter, P.
Since the vast majority of global seafloor habitats are characterized by soft sediments, hard substrata represent rarities hosting species and functional groups not found elsewhere. The same holds true for the enclosed and brackish Baltic Sea, where hard substrata occur patchy and infrequent. Subtidal low-relief terrains with homogenous mud and sand flats form the predominant benthic substrate and the associated infaunal communities are well described. In contrast, the diverse, primarily epibenthic assemblages on subtidal hard bottoms received far less attention. Since 2011 a team of geologists and biologists aims to map the subtidal habitats and biotopes. On joint cruises, geologists use side scan sonar to map the seafloor sediments while ground truthing is performed in collaboration with biologists. Biogenic concretions like mussel beds and hard structures of geogenic origin like stones and glacial boulders form the predominant hard substrata in the German Baltic Sea. These habitats are subsequently investigated using frame sampling by SCUBA diving, dredges or towed photo/video platforms. The type of hard substratum, salinity and light availability seem to be the most important natural factors that determine the epibenthic community composition. Identified geological substrata and biological communities are matched with biotopes of the HELCOM Underwater biotope and habitat classification system. Predictive modeling approaches are used to generate biotope specific distribution patterns, based on biological point samples, area-wide sediment distribution maps and measured/modeled environmental parameters. The resulting hard-bottom biotope maps, combining geological and biological information, complement the existing area-wide biotope map of soft sediment communities. The maps are important tools both for the scientific community to understand the functioning of marine ecosystems as well as for nature conservation, e.g. for the implementation of MPA management plans
Theoretical considerations on multiparton interactions in QCD
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Schaefer, Andreas [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik
We investigate several ingredients for a theory of multiple hard scattering in hadronhadron collisions. Issues discussed include the space-time structure of multiple interactions, their power behavior, spin and color correlations, interference terms, scale evolution and Sudakov logarithms. We discuss possibilities to constrain multiparton distributions by lattice calculations and by connecting them with generalized parton distributions. We show that the behavior of two-parton distributions at small interparton distances leads to problems with ultraviolet divergences and with double counting, which requires modification of the presently available theoretical framework. (orig.)
Illustration of Uncertainties in Assessments of Flow and Transport in a Block Scale Fracture Network an Example from the Äspö Hard Rock Laboratory, Sweden.
Poteri, A.; Cvetkovic, V.; Dershowitz, W.; Billaux, D.; Winberg, A.
Tracer experiments have been performed since 1995 at the underground SKB Äspö Hard Rock Laboratory, southeastern Sweden. Non-sorbing and sorbing radioactive tracer experiments of the TRUE Block Scale Project were conducted in single fractures and a network of fractures with support from a comprehensive program of laboratory experiments, geological, hydrogeological and hydrogeochemical characterisation and associated modelling. The collected information have resulted in the definition of two generalised fracture types, one fault type with fault gouge (Type 1) and one non-fault type (Type 2) without fault gouge, the latter corresponding to background fractures. These two generic fracture types were characterized by a multiple immobile zone porosity model, referred to as the "microstructural model". Understanding gained from the TRUE Block Scale Project was used to investigate and model a previously non- tested part of the investigated rock volume. These "predictive" experiments were carried out to test and improve our conceptual understanding of solute transport in fractured rocks, and to demonstrate the current state of our predictive capabilities. The modelling included assessment of effects of geometry, macro- structure, and micro-structure, with a particular focus on the role of lower conductivity background fractures within transport pathways. Following a basic characterisation including tracer dilution and non-reactive tracer pre-tests, sorbing tracer tests were conducted in a) a single Type 1 fracture flow path and b) a flow path involving injection in a single background fracture of Type 2 connected to a major Type 1 structure. The structural model characterization of the rock indicated that the Type 1 pathway has a path length comparable to the Euclidian distance of about 20 m, but the background fracture pathways including both Type 1 and Type 2 fractures, although with an Euclidian similar to the single structure Type 1 pathway, in fact has an evaluated
QCD sum rule studies at finite density and temperature
Energy Technology Data Exchange (ETDEWEB)
Kwon, Youngshin
In-medium modifications of hadronic properties have a strong connection to the restoration of chiral symmetry in hot and/or dense medium. The in-medium spectral functions for vector and axial-vector mesons are of particular interest in this context, considering the experimental dilepton production data which signal the in-medium meson properties. In this thesis, finite energy sum rules are employed to set constraints for the in-medium spectral functions of vector and axial-vector mesons. Finite energy sum rules for the first two moments of the spectral functions are investigated with emphasis on the role of a scale parameter related to the spontaneous chiral symmetry breaking in QCD. It is demonstrated that these lowest moments of vector current spectral functions do permit an accurate sum rule analysis with controlled inputs, such as the QCD condensates of lowest dimensions. In contrast, the higher moments contain uncertainties from the higher dimensional condensates. It turns out that the factorization approximation for the four-quark condensate is not applicable in any of the cases studied in this work. The accurate sum rules for the lowest two moments of the spectral functions are used to clarify and classify the properties of vector meson spectral functions in a nuclear medium. Possible connections with the Brown-Rho scaling hypothesis are also discussed. (orig.)
The accuracy of QCD perturbation theory at high energies
Dalla Brida, Mattia; Korzec, Tomasz; Ramos, Alberto; Sint, Stefan; Sommer, Rainer
We discuss the determination of the strong coupling $\\alpha_\\mathrm{\\overline{MS}}^{}(m_\\mathrm{Z})$ or equivalently the QCD $\\Lambda$-parameter. Its determination requires the use of perturbation theory in $\\alpha_s(\\mu)$ in some scheme, $s$, and at some energy scale $\\mu$. The higher the scale $\\mu$ the more accurate perturbation theory becomes, owing to asymptotic freedom. As one step in our computation of the $\\Lambda$-parameter in three-flavor QCD, we perform lattice computations in a scheme which allows us to non-perturbatively reach very high energies, corresponding to $\\alpha_s = 0.1$ and below. We find that perturbation theory is very accurate there, yielding a three percent error in the $\\Lambda$-parameter, while data around $\\alpha_s \\approx 0.2$ is clearly insufficient to quote such a precision. It is important to realize that these findings are expected to be generic, as our scheme has advantageous properties regarding the applicability of perturbation theory.
Meissner, Marco
The LHCb detector at the LHC has a unique peudorapidity coverage (2 < $\\eta$ < 5) which allows to perform soft QCD measurements in the kinematic forward region where QCD models have large uncertainties. Selected analyses on soft QCD measurements in $pp$ collisions are summarised in these proceedings. The energy flow has been measured separately for different event classes allowing to probe multi-parton interactions at large $\\eta$. The measured prompt hadron ratios are important for hadronisation models, while the $\\bar{p}/p$ is a good observable to test models of baryon number transport. Charm production has been studied to determine cross-sections and production ratios. All measurements are compared to Monte Carlo simulation or theory predictions.
Exploring hyperons and hypernuclei with lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Beane, S.R.; Bedaque, P.F.; Parreno, A.; Savage, M.J.
In this work we outline a program for lattice QCD that wouldprovide a first step toward understanding the strong and weakinteractions of strange baryons. The study of hypernuclear physics hasprovided a significant amount of information regarding the structure andweak decays of light nuclei containing one or two Lambda's, and Sigma's.From a theoretical standpoint, little is known about the hyperon-nucleoninteraction, which is required input for systematic calculations ofhypernuclear structure. Furthermore, the long-standing discrepancies inthe P-wave amplitudes for nonleptonic hyperon decays remain to beunderstood, and their resolution is central to a better understanding ofthe weak decays of hypernuclei. We present a framework that utilizesLuscher's finite-volume techniques in lattice QCD to extract thescattering length and effective range for Lambda-N scattering in both QCDand partially-quenched QCD. The effective theory describing thenonleptonic decays of hyperons using isospin symmetry alone, appropriatefor lattice calculations, is constructed.
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; de Teramond, Guy F.; /SLAC /Southern Denmark U., CP3-Origins /Costa Rica U.
AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its {beta}-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.
New Methods in Non-Perturbative QCD
Energy Technology Data Exchange (ETDEWEB)
Unsal, Mithat [North Carolina State Univ., Raleigh, NC (United States)
In this work, we investigate the properties of quantum chromodynamics (QCD), by using newly developing mathematics and physics formalisms. Almost all of the mass in the visible universe emerges from a quantum chromodynamics (QCD), which has a completely negligible microscopic mass content. An intimately related issue in QCD is the quark confinement problem. Answers to non-perturbative questions in QCD remained largely elusive despite much effort over the years. It is also believed that the usual perturbation theory is inadequate to address these kinds of problems. Perturbation theory gives a divergent asymptotic series (even when the theory is properly renormalized), and there are non-perturbative phenomena which never appear at any order in perturbation theory. Recently, a fascinating bridge between perturbation theory and non-perturbative effects has been found: a formalism called resurgence theory in mathematics tells us that perturbative data and non-perturbative data are intimately related. Translating this to the language of quantum field theory, it turns out that non-perturbative information is present in a coded form in perturbation theory and it can be decoded. We take advantage of this feature, which is particularly useful to understand some unresolved mysteries of QCD from first principles. In particular, we use: a) Circle compactifications which provide a semi-classical window to study confinement and mass gap problems, and calculable prototypes of the deconfinement phase transition; b) Resurgence theory and transseries which provide a unified framework for perturbative and non-perturbative expansion; c) Analytic continuation of path integrals and Lefschetz thimbles which may be useful to address sign problem in QCD at finite density.
Threshold resummation in SCET vs. perturbative QCD. An analytic comparison
Energy Technology Data Exchange (ETDEWEB)
Bonvini, Marco [Genoa Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Genoa (Italy); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Forte, Stefano [Milano Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Milan (Italy); Ghezzi, Margherita [Milano Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Milan (Italy); Rome Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Rome (Italy); Ridolfi, Giovanni [Genoa Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Genoa (Italy)
We compare threshold resummation in QCD, as performed using soft-collinear effective theory (SCET), to the standard perturbative QCD formalism based on factorization and resummation of Mellin moments of partonic cross-sections. We consider various forms of the SCET result, which correspond to different choices of the soft scale {mu}{sub s} that characterizes this approach. We derive a master formula that relates the SCET resummation to the QCD result for any choice of {mu}{sub s}. We then use it first, to show that if SCET resummation is performed in N-Mellin moment space by suitable choice of {mu}{sub s} it is equivalent to the standard perturbative approach. Next, we show that if SCET resummation is performed by choosing for {mu}{sub s} a partonic momentum variable, the perturbative result for partonic resummed cross-sections is again reproduced, but like its standard perturbative counterpart it is beset by divergent behaviour at the endpoint. Finally, using the master formula we show that when {mu}{sub s} is chosen as a hadronic momentum variable the SCET and standard approach are related through a multiplicative (convolutive) factor, which contains the dependence on the Landau pole and associated divergence. This factor depends on the luminosity in a non-universal way; it lowers by one power of log the accuracy of the resummed result, but it is otherwise subleading if one assumes the luminosity not to contain logarithmically enhanced terms. Therefore, the SCET approach can be turned into a prescription to remove the Landau pole from the perturbative result, but the price to pay for this is the reduction by one logarithmic power of the accuracy at each order and the need to make assumptions on the parton luminosity. (orig.)
Higher order QCD corrections in small x physics
Energy Technology Data Exchange (ETDEWEB)
Chachamis, G.
We study higher order QCD corrections in small x Physics. The numerical implementation of the full NLO photon impact factor is the remaining necessary piece for the testing of the NLO BFKL resummation against data from physical processes, such as {gamma}{sup *}{gamma}{sup *} collisions. We perform the numerical integration over phase space for the virtual corrections to the NLO photon impact factor. This, along with the previously calculated real corrections, makes feasible in the near future first estimates for the {gamma}*{gamma}* total cross section, since the convolution of the full impact factor with the NLO BFKL gluon Green's function is now straightforward. The NLO corrections for the photon impact factor are sizeable and negative. In the second part of this thesis, we estimate higher order correction to the BK equation. We are mainly interested in whether partonic saturation delays or not in rapidity when going beyond the leading order. In our investigation, we use the so called 'rapidity veto' which forbid two emissions to be very close in rapidity, to 'switch on' higher order corrections to the BK equation. From analytic and numerical analysis, we conclude that indeed saturation does delay in rapidity when higher order corrections are taken into account. In the last part, we investigate higher order QCD corrections as additional corrections to the Electroweak (EW) sector. The question of whether BFKL corrections are of any importance in the Regge limit for the EW sector seems natural; although they arise in higher loop level, the accumulation of logarithms in energy s at high energies, cannot be dismissed without an investigation. We focus on the process {gamma}{gamma}{yields}ZZ. We calculate the pQCD corrections in the forward region at leading logarithmic (LL) BFKL accuracy, which are of the order of few percent at the TeV energy scale. (orig.)
A Framework for Lattice QCD Calculations on GPUs
Energy Technology Data Exchange (ETDEWEB)
Winter, Frank; Clark, M A; Edwards, Robert G; Joo, Balint
Computing platforms equipped with accelerators like GPUs have proven to provide great computational power. However, exploiting such platforms for existing scientific applications is not a trivial task. Current GPU programming frameworks such as CUDA C/C++ require low-level programming from the developer in order to achieve high performance code. As a result porting of applications to GPUs is typically limited to time-dominant algorithms and routines, leaving the remainder not accelerated which can open a serious Amdahl's law issue. The lattice QCD application Chroma allows to explore a different porting strategy. The layered structure of the software architecture logically separates the data-parallel from the application layer. The QCD Data-Parallel software layer provides data types and expressions with stencil-like operations suitable for lattice field theory and Chroma implements algorithms in terms of this high-level interface. Thus by porting the low-level layer one can effectively move the whole application in one swing to a different platform. The QDP-JIT/PTX library, the reimplementation of the low-level layer, provides a framework for lattice QCD calculations for the CUDA architecture. The complete software interface is supported and thus applications can be run unaltered on GPU-based parallel computers. This reimplementation was possible due to the availability of a JIT compiler (part of the NVIDIA Linux kernel driver) which translates an assembly-like language (PTX) to GPU code. The expression template technique is used to build PTX code generators and a software cache manages the GPU memory. This reimplementation allows us to deploy an efficient implementation of the full gauge-generation program with dynamical fermions on large-scale GPU-based machines such as Titan and Blue Waters which accelerates the algorithm by more than an order of magnitude.
Playing with QCD I: effective field theories
Energy Technology Data Exchange (ETDEWEB)
Fraga, Eduardo S. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Inst. de Fisica
The building blocks of hadrons are quarks and gluons, although color is confined into singlet states. QCD is believed to be the fundamental theory of strong interactions. Its asymptotically free nature puts the vacuum out of reach for perturbation theory. The Lagrangian of QCD and the Feynman rules associated were built by using the Gauge Principle, starting from the quark matter fields and obtaining gluons as connections. A simpler, and sometimes necessary or complementary, approach is provided by effective field theories or effective models, especially when one has to deal with the nonperturbative sector of the theory. (author)
QCD unitarity constraints on Reggeon Field Theory
Energy Technology Data Exchange (ETDEWEB)
Kovner, Alex [Physics Department, University of Connecticut,2152 Hillside Road, Storrs, CT 06269 (United States); Levin, Eugene [Departemento de Física, Universidad Técnica Federico Santa María,and Centro Científico-Tecnológico de Valparaíso,Avda. Espana 1680, Casilla 110-V, Valparaíso (Chile); Department of Particle Physics, Tel Aviv University,Tel Aviv 69978 (Israel); Lublinsky, Michael [Physics Department, Ben-Gurion University of the Negev,Beer Sheva 84105 (Israel); Physics Department, University of Connecticut,2152 Hillside Road, Storrs, CT 06269 (United States)
We point out that the s-channel unitarity of QCD imposes meaningful constraints on a possible form of the QCD Reggeon Field Theory. We show that neither the BFKL nor JIMWLK nor Braun's Hamiltonian satisfy the said constraints. In a toy, zero transverse dimensional case we construct a model that satisfies the analogous constraint and show that at infinite energy it indeed tends to a "black disk limit' as opposed to the model with triple Pomeron vertex only, routinely used as a toy model in the literature.
Recent QCD results from the Tevatron
Wobisch, M
Recent QCD related results from the CDF and the D0 experiments are presented based on proton anti-proton collision data at sqrt(s)=1.96 TeV, taken in Run II of the Fermilab Tevatron Collider. Measured observables include inclusive photon and diphoton production, vector boson plus jets production, event shape variables, and inclusive multijet production. The measurement results are compared to QCD theory calculations in different approximations. A determination of the strong coupling constant from jet data is presented.
QCD measurements with the CMS detector
CERN. Geneva
In the first year of LHC data taking, CMS pursued a rich program of QCD physics. In the low-pt front, results on momentum-, pseudorapidity- and multiplicity distributions of charged and strange hadrons, underlying event observables, two particle rapidity correlations and Bose-Einstein correlations are presented. In the high-pt front, jet and photon cross-section measurements are reported on inclusive and di-object production, as well as ratios of 3/2 jet cross sections. Finally, the QCD multi-jet dynamics is explored with event-shapes variables, dijet azimuthal decorrelations and dijet angular distributions
Automation of one-loop QCD corrections
Hirschi, Valentin; Frixione, Stefano; Garzelli, Maria Vittoria; Maltoni, Fabio; Pittau, Roberto
We present the complete automation of the computation of one-loop QCD corrections, including UV renormalization, to an arbitrary scattering process in the Standard Model. This is achieved by embedding the OPP integrand reduction technique, as implemented in CutTools, into the MadGraph framework. By interfacing the tool so constructed, which we dub MadLoop, with MadFKS, the fully automatic computation of any infrared-safe observable at the next-to-leading order in QCD is attained. We demonstrate the flexibility and the reach of our method by calculating the production rates for a variety of processes at the 7 TeV LHC.
Hadron scattering and resonances in QCD
Energy Technology Data Exchange (ETDEWEB)
Dudek, Jozef J. [Old Dominion Univ., Norfolk, VA (United States)
I describe how hadron-hadron scattering amplitudes are related to the eigenstates of QCD in a finite cubic volume. The discrete spectrum of such eigenstates can be determined from correlation functions computed using lattice QCD, and the corresponding scattering amplitudes extracted. I review results from the Hadron Spectrum Collaboration who have used these finite volume methods to study pi pi elastic scattering, including the rho resonance, as well as coupled-channel pi K, eta K scattering. Ongoing calculations are advertised and the outlook for finite volume approaches is presented.
Hadron mass spectrum from lattice QCD.
Majumder, Abhijit; Müller, Berndt
Finite temperature lattice simulations of quantum chromodynamics (QCD) are sensitive to the hadronic mass spectrum for temperatures below the "critical" temperature T(c) ≈ 160 MeV. We show that a recent precision determination of the QCD trace anomaly shows evidence for the existence of a large number of hadron states beyond those known from experiment. The lattice results are well represented by an exponentially growing mass spectrum up to a temperature T=155 MeV. Using simple parametrizations of the hadron mass spectrum we show how one may estimate the total spectral weight in these yet undermined states.
Progress in the theory of hard exclusive processes
Energy Technology Data Exchange (ETDEWEB)
Gousset, T. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l`Instrumentation Associee; Pire, B. [Ecole Polytechnique, 91 - Palaiseau (France). Centre de Physique Theorique
Recent progresses in the theory of hard exclusive processes are reviewed. The hard scattering mechanism and the factorization of perturbative QCD amplitudes from wave-function-like quantities is now well understood. The effects of soft gluon radiation are controlled through Sudakov form factors which protect observables from dangerous end-point contributions. The phenomenology of this mature framework is eagerly waiting for precise experimental data in a domain where transfers are O(10 GeV{sup 2}). (author). 11 refs., 2 figs.
Supporting the search for the CEP location with nonlocal PNJL models constrained by lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Contrera, Gustavo A. [IFLP, UNLP, CONICET, Facultad de Ciencias Exactas, La Plata (Argentina); Gravitation, Astrophysics and Cosmology Group, FCAyG, UNLP, La Plata (Argentina); CONICET, Buenos Aires (Argentina); Grunfeld, A.G. [CONICET, Buenos Aires (Argentina); Comision Nacional de Energia Atomica, Departamento de Fisica, Buenos Aires (Argentina); Blaschke, David [University of Wroclaw, Institute of Theoretical Physics, Wroclaw (Poland); Joint Institute for Nuclear Research, Moscow Region (Russian Federation); National Research Nuclear University (MEPhI), Moscow (Russian Federation)
We investigate the possible location of the critical endpoint in the QCD phase diagram based on nonlocal covariant PNJL models including a vector interaction channel. The form factors of the covariant interaction are constrained by lattice QCD data for the quark propagator. The comparison of our results for the pressure including the pion contribution and the scaled pressure shift Δ P/T {sup 4} vs. T/T{sub c} with lattice QCD results shows a better agreement when Lorentzian form factors for the nonlocal interactions and the wave function renormalization are considered. The strength of the vector coupling is used as a free parameter which influences results at finite baryochemical potential. It is used to adjust the slope of the pseudocritical temperature of the chiral phase transition at low baryochemical potential and the scaled pressure shift accessible in lattice QCD simulations. Our study, albeit presently performed at the mean-field level, supports the very existence of a critical point and favors its location within a region that is accessible in experiments at the NICA accelerator complex. (orig.)
Determination of {{\\rm{\\Lambda }}}_{\\overline{{\\rm{MS}}}} at five loops from holographic QCD
Deur, Alexandre; Brodsky, Stanley J.; de Téramond, Guy F.
The recent determination of the β-function of the quantum chromodynamics (QCD) running coupling {α }\\overline{{{MS}}}({Q}2) to five-loops, provides a verification of the convergence of a novel method for determining the fundamental QCD parameter {{{Λ }}}s based on the light-front holographic approach to nonperturbative QCD. The new five-loop analysis, together with improvements in determining the holographic QCD nonperturbative scale parameter κ from hadronic spectroscopy, leads to an improved precision of the value of {{{Λ }}}s in the \\overline{{{MS}}} scheme close to a factor of two; we find {{{Λ }}}\\overline{{{MS}}}(3)=0.339+/- 0.019 {GeV} for {n}f=3, in excellent agreement with the world average, {{{Λ }}}\\overline{{{MS}}}(3)=0.332 +/- 0.017 {GeV}. We also discuss the constraints imposed on the scale dependence of the strong coupling in the nonperturbative domain by superconformal quantum mechanics and its holographic embedding in anti-de Sitter space.
Nonlinear dynamics of soft fermion excitations in hot QCD plasma I: soft-quark - soft-gluon scattering
Markov, Yu. A.; Markova, M. A.
Within the framework of the hard thermal loop effective theory we derive a system of Boltzmann-like kinetic equations taking into account the simplest processes of nonlinear interaction of soft fermionic and bosonic QCD plasma excitations: elastic scattering of soft-(anti)quark excitations off soft-gluon and soft-quark excitations, pair production of soft quark-antiquark excitations, annihilation into two soft-gluon excitations. The matrix elements of these processes to leading order in the c...
The strange quark mass and Lambda parameter of two flavor QCD
Energy Technology Data Exchange (ETDEWEB)
Fritzsch, Patrick; Marinkovic, Marina [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Knechtli, Francesco; Leder, Bjoern [Wuppertal Univ. (Germany). Fachbereich C - Mathematik und Naturwissenschaften; Schaefer, Stefan [CERN, Geneva (Switzerland). Physics Dept.; Sommer, Rainer; Virotta, Francesco [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
We complete the non-perturbative calculations of the strange quark mass and the {lambda} parameter in two flavor QCD by the ALPHA collaboration. The missing lattice scale is determined via the kaon decay constant, for whose chiral extrapolation complementary strategies are compared. We also give a value for the scale r{sub 0} in physical units as well as an improved determination of the renormalization constant Z{sub A}.
Lattice QCD with strong external electric fields
Yamamoto, Arata
We study particle generation by a strong electric field in lattice QCD. To avoid the sign problem of the Minkowskian electric field, we adopt the "isospin" electric charge. When a strong electric field is applied, the insulating vacuum is broken down and pairs of charged particles are produced by the Schwinger mechanism. The competition against the color confining force is also discussed.
QCDNUM: fast QCD evolution and convolution
Botje, M.A.J.|info:eu-repo/dai/nl/070139032
The QCDNUM program numerically solves the evolution equations for parton densities and fragmentation functions in perturbative QCD. Un-polarised parton densities can be evolved up to next-to-next-to-leading order in powers of the strong coupling constant, while polarised densities or fragmentation
Lattice investigations of the QCD phase diagram
Energy Technology Data Exchange (ETDEWEB)
Guenther, Jana
To understand the physics in the early universe as well as in heavy ion collisions a throughout understanding of the theory of strong interaction, quantum chromodynamics (QCD), is important. Lattice QCD provides a tool to study it from first principles. However due to the sign problem direct simulations with physical conditions are at the moment limited to zero chemical potential. In this thesis I present a circumvention of this problem. We can gain information on the QCD phase diagram and the equation of state from analytical continuation of results extracted from simulations at imaginary chemical potential. The topological susceptibility is very expensive to compute in Lattice QCD. However it provides an important ingredient for the estimation of the axion mass. The axion is a possible candidate for a dark matter, which plays in important role in the understanding of our universe. In this thesis I discuss two techniques that make it possible to determine the topological susceptibility and allow for an estimation of the axion mass. I then use this mass restrain to analyze the idea of an experiment to detect axions with a dielectric mirror.
Dual of QCD with One Adjoint Fermion
DEFF Research Database (Denmark)
Mojaza, Matin; Nardecchia, Marco; Pica, Claudio
We construct the magnetic dual of QCD with one adjoint Weyl fermion. The dual is a consistent solution of the 't Hooft anomaly matching conditions, allows for flavor decoupling and remarkably constitutes the first nonsupersymmetric dual valid for any number of colors. The dual allows to bound the...
Energy Technology Data Exchange (ETDEWEB)
The role of the top quark in completing the Standard Model quark sector is reviewed, along with a discussion of production, decay, and theoretical restrictions on the top quark properties. Particular attention is paid to the top quark as a laboratory for perturbative QCD. As examples of the relevance of QCD corrections in the top quark sector, the calculation of e{sup +}e{sup -} + t{bar t} at next-to-leading-order QCD using the phase space slicing algorithm and the implications of a precision measurement of the top quark mass are discussed in detail. The associated production of a t{bar t} pair and a Higgs boson in either e{sup +}e{sup -} or hadronic collisions is presented at next-to-leading-order QCD and its importance for a measurement of the top quark Yulrawa coupling emphasized. Implications of the heavy top quark mass for model builders are briefly examined, with the minimal supersymmetric Standard Model and topcolor discussed as specific examples.
Nonperturbative QCD corrections to electroweak observables
Energy Technology Data Exchange (ETDEWEB)
Renner, Dru B. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Feng, Xu [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki (Japan); Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Petschlies, Marcus [The Cyprus Institute, Nicosia (Cyprus)
Nonperturbative QCD corrections are important to many low-energy electroweak observables, for example the muon magnetic moment. However, hadronic corrections also play a significant role at much higher energies due to their impact on the running of standard model parameters, such as the electromagnetic coupling. Currently, these hadronic contributions are accounted for by a combination of experimental measurements, effective field theory techniques and phenomenological modeling but ideally should be calculated from first principles. Recent developments indicate that many of the most important hadronic corrections may be feasibly calculated using lattice QCD methods. To illustrate this, we examine the lattice computation of the leading-order QCD corrections to the muon magnetic moment, paying particular attention to a recently developed method but also reviewing the results from other calculations. We then continue with several examples that demonstrate the potential impact of the new approach: the leading-order corrections to the electron and tau magnetic moments, the running of the electromagnetic coupling, and a class of the next-to-leading-order corrections for the muon magnetic moment. Along the way, we mention applications to the Adler function, which can be used to determine the strong coupling constant, and QCD corrections to muonic-hydrogen.
Probing hadron wave functions in Lattice QCD
Alexandrou, C; Tsapalis, A; Forcrand, Ph. de
Gauge-invariant equal-time correlation functions are calculated in lattice QCD within the quenched approximation and with two dynamical quark species. These correlators provide information on the shape and multipole moments of the pion, the rho, the nucleon and the $\\Delta$.
Feynman integrals in QCD made simple
CERN. Geneva
A key insight is that important properties of these functions can be predicted by inspecting the singularity structure of the Feynman integrand. Combined with the differential equations technique, this gives a powerful method for computing the necessary Feynman integrals. I will review these ideas, based on Phys.Rev.Lett. 110 (2013) 25, and present recent new results relevant for QCD scattering amplitudes.
Exploring Hyperons and Hypernuclei with Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
S.R. Beane; P.F. Bedaque; A. Parreno; M.J. Savage
In this work we outline a program for lattice QCD that would provide a first step toward understanding the strong and weak interactions of strange baryons. The study of hypernuclear physics has provided a significant amount of information regarding the structure and weak decays of light nuclei containing one or two Lambda's, and Sigma's. From a theoretical standpoint, little is known about the hyperon-nucleon interaction, which is required input for systematic calculations of hypernuclear structure. Furthermore, the long-standing discrepancies in the P-wave amplitudes for nonleptonic hyperon decays remain to be understood, and their resolution is central to a better understanding of the weak decays of hypernuclei. We present a framework that utilizes Luscher's finite-volume techniques in lattice QCD to extract the scattering length and effective range for Lambda-N scattering in both QCD and partially-quenched QCD. The effective theory describing the nonleptonic decays of hyperons using isospin symmetry alone, appropriate for lattice calculations, is constructed.
Two flavor QCD and confinement - II
DEFF Research Database (Denmark)
Cossu, G.; D'Elia, M.; Di Giacomo, A.
This paper is part of a program of investigation of the chiral transition in Nf=2 QCD, started in Phys.Rev.D72:114510,2005. Progress is reported on theunderstanding of some possible systematic errors. A direct test of first orderscaling is presented....
QCD string model for hybrid adiabatic potentials
Kalashnikova, Yu. S.; Kuzmenko, D. S.
Hybrid adiabatic potentials are considered in the framework of the QCD string model. The einbein field formalism is applied to obtain the large-distance behaviour of adiabatic potentials. The calculated excitation curves are shown to be the result of interplay between potential-type longitudinal and string-type transverse vibrations. The results are compared with recent lattice data.
Frontiers of finite temperature lattice QCD
Directory of Open Access Journals (Sweden)
Borsányi Szabolcs
Full Text Available I review a selection of recent finite temperature lattice results of the past years. First I discuss the extension of the equation of state towards high temperatures and finite densities, then I show recent results on the QCD topological susceptibility at high temperatures and highlight its relevance for dark matter search.
A QCD analysis of ZEUS diffractive data
Energy Technology Data Exchange (ETDEWEB)
Chekanov, S.; Derrick, M.; Magill, S. [Argonne National Laboratory, Argonne, IL (US)] (and others)
ZEUS inclusive diffractive cross-section measurements have been used in a DGLAP next-to-leading-order QCD analysis to extract the diffractive parton distribution functions. Data on diffractive dijet production in deep inelastic scattering have also been included to constrain the gluon density. Predictions based on the extracted parton densities are compared to diffractive charm and dijet photoproduction data. (orig.)
Energy Technology Data Exchange (ETDEWEB)
The title of the workshop, ''The QCD Phase Transitions'', in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discussion of the underlying non-perturbative mechanisms which manifest themselves as all those phases. Before we go to specifics, let us emphasize one important aspect of the present status of non-perturbative Quantum Field Theory in general. It remains true that its studies do not get attention proportional to the intellectual challenge they deserve, and that the theorists working on it remain very fragmented. The efforts to create Theory of Everything including Quantum Gravity have attracted the lion share of attention and young talent. Nevertheless, in the last few years there was also a tremendous progress and even some shift of attention toward emphasis on the unity of non-perturbative phenomena. For example, we have seen some. efforts to connect the lessons from recent progress in Supersymmetric theories with that in QCD, as derived from phenomenology and lattice. Another example is Maldacena conjecture and related development, which connect three things together, string theory, super-gravity and the (N=4) supersymmetric gauge theory. Although the progress mentioned is remarkable by itself, if we would listen to each other more we may have chance to strengthen the field and reach better understanding of the spectacular non-perturbative physics.
The Top Quark, QCD, And New Physics.
Dawson, S.
The role of the top quark in completing the Standard Model quark sector is reviewed, along with a discussion of production, decay, and theoretical restrictions on the top quark properties. Particular attention is paid to the top quark as a laboratory for perturbative QCD. As examples of the relevance of QCD corrections in the top quark sector, the calculation of e{sup+}e{sup -}+ t{bar t} at next-to-leading-order QCD using the phase space slicing algorithm and the implications of a precision measurement of the top quark mass are discussed in detail. The associated production of a t{bar t} pair and a Higgs boson in either e{sup+}e{sup -} or hadronic collisions is presented at next-to-leading-order QCD and its importance for a measurement of the top quark Yulrawa coupling emphasized. Implications of the heavy top quark mass for model builders are briefly examined, with the minimal supersymmetric Standard Model and topcolor discussed as specific examples.
Nonperturbative QCD corrections to electroweak observables
Energy Technology Data Exchange (ETDEWEB)
Dru B Renner, Xu Feng, Karl Jansen, Marcus Petschlies
Nonperturbative QCD corrections are important to many low-energy electroweak observables, for example the muon magnetic moment. However, hadronic corrections also play a significant role at much higher energies due to their impact on the running of standard model parameters, such as the electromagnetic coupling. Currently, these hadronic contributions are accounted for by a combination of experimental measurements and phenomenological modeling but ideally should be calculated from first principles. Recent developments indicate that many of the most important hadronic corrections may be feasibly calculated using lattice QCD methods. To illustrate this, we will examine the lattice computation of the leading-order QCD corrections to the muon magnetic moment, paying particular attention to a recently developed method but also reviewing the results from other calculations. We will then continue with several examples that demonstrate the potential impact of the new approach: the leading-order corrections to the electron and tau magnetic moments, the running of the electromagnetic coupling, and a class of the next-to-leading-order corrections for the muon magnetic moment. Along the way, we will mention applications to the Adler function, the determination of the strong coupling constant and QCD corrections to muonic-hydrogen.
Visualization Tools for Lattice QCD - Final Report
Energy Technology Data Exchange (ETDEWEB)
Massimo Di Pierro
Our research project is about the development of visualization tools for Lattice QCD. We developed various tools by extending existing libraries, adding new algorithms, exposing new APIs, and creating web interfaces (including the new NERSC gauge connection web site). Our tools cover the full stack of operations from automating download of data, to generating VTK files (topological charge, plaquette, Polyakov lines, quark and meson propagators, currents), to turning the VTK files into images, movies, and web pages. Some of the tools have their own web interfaces. Some Lattice QCD visualization have been created in the past but, to our knowledge, our tools are the only ones of their kind since they are general purpose, customizable, and relatively easy to use. We believe they will be valuable to physicists working in the field. They can be used to better teach Lattice QCD concepts to new graduate students; they can be used to observe the changes in topological charge density and detect possible sources of bias in computations; they can be used to observe the convergence of the algorithms at a local level and determine possible problems; they can be used to probe heavy-light mesons with currents and determine their spatial distribution; they can be used to detect corrupted gauge configurations. There are some indirect results of this grant that will benefit a broader audience than Lattice QCD physicists.
Testing QCD in Photon-Photon Interactions
Soldner-Rembold, Stefan
At high energies photon-photon interactions are dominated by quantum fluctuations of the photons into fermion-antifermion pairs and into vector mesons. This is called photon structure. Electron-positron collisions at LEP are an ideal laboratory for studying photon structure and for testing QCD.
Introduction to chiral symmetry in QCD
Directory of Open Access Journals (Sweden)
Sazdjian H.
Full Text Available The main aspects of chiral symmetry in QCD are presented. The necessity of its spontaneous breakdown is explained. Some low-energy theorems are reviewed. The role of chiral effective Lagrangians in the formulation and realization of chiral perturbation theory is emphasized. The consequences of the presence of anomalies are sketched.
Dimensionally regularized Polyakov loop correlators in hot QCD
Burnier, Y.; Laine, M.; Vepsäläinen, M.
A popular observable in finite-temperature lattice QCD is the so-called singlet quark-antiquark free energy, conventionally defined in Coulomb gauge. In an effort to interpret the existing numerical data on this observable, we compute it at order mathcal{O}left( {α_s^2} right) in continuum, and analyze the result at various distance scales. At short distances ( r ≪ 1/ πT) the behaviour matches that of the gauge-independent zero-temperature potential; on the other hand at large distances ( r ≫ 1/ πT) the singlet free energy appears to have a gauge-fixing related power-law tail. At infinite distance the result again becomes physical in the sense that it goes over to a gauge-independent disconnected contribution, the square of the expectation value of the trace of the Polyakov loop; we recompute this quantity at mathcal{O}left( {α_s^2} right) , finding for pure SU( N c ) a different non-logarithmic term than in previous literature, and adding for full QCD the quark contribution. We also discuss the value of the singlet free energy in a general covariant gauge, as well as the behaviour of the cyclic Wilson loop that is obtained if the singlet free energy is made gauge-independent by inserting straight spacelike Wilson lines into the observable. Comparisons with lattice data are carried out where possible.
Exploring QCD dynamics in medium energy γA semiexclusive collisions
Directory of Open Access Journals (Sweden)
A.B. Larionov
Full Text Available We demonstrate that studies of the semiexclusive large angle photon–nucleus reactions: γ+A→h1+h2+(A−1⁎ with tagged photon beams of energies 6÷10 GeV which can be performed in Hall D at Thomas Jefferson National Acceleration Facility (TJNAF would allow to probe several aspects of the QCD dynamics: establish the t-range in which transition from soft to hard dynamics occurs, compare the strength of the interaction of various mesons and baryons with nucleons at the energies of few GeV, as well as look for the color transparency effects.
The QCD pomeron at TESLA motivation and exclusive $J/\\psi$ production
Kwiecinski, J.; De Roeck, A.
We briefly present the motivation for studying the processes mediated by the QCD pomeron at high energy e+e- colliders. We describe the behaviour of the cross-section for the reaction gamma gamma to J/psi J/psi obtained from the BFKL equation with dominant non-leading corrections. We give the predictions for the rates of anti-tagged e+e- to e+e- J/psi J/psi events in TESLA and conclude that such reactions may be excellent probes of the hard pomeron.
Higgs boson gluon-fusion production beyond threshold in N$^3$LO QCD
Anastasiou, Charalampos; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Mistlberger, Bernhard
In this article, we compute the gluon fusion Higgs boson cross-section at N3LO through the second term in the threshold expansion. This calculation constitutes a major milestone towards the full N3LO cross section. Our result has the best formal accuracy in the threshold expansion currently available, and includes contributions from collinear regions besides subleading corrections from soft and hard regions, as well as certain logarithmically enhanced contributions for general kinematics. We use our results to perform a critical appraisal of the validity of the threshold approximation at N3LO in perturbative QCD.
GPDs at non-zero skewness in ADS/QCD model
Directory of Open Access Journals (Sweden)
Matteo Rinaldi
Full Text Available We study Generalized Parton Distribution functions (GPDs usually measured in hard exclusive processes and encoding information on the three dimensional partonic structure of hadrons and their spin decomposition, for non-zero skewness within the AdS/QCD formalism. To this aim the canonical scheme to calculate GPDs at zero skewness has been properly generalized. Furthermore, we show that the latter quantities, in this non-forward regime, are sensitive to non-trivial details of the hadronic light front wave function, such as a kind of parton correlations usually not accessible in studies of form factors and GPDs at zero skewness.
GPDs at non-zero skewness in ADS/QCD model
Rinaldi, Matteo
We study Generalized Parton Distribution functions (GPDs) usually measured in hard exclusive processes and encoding information on the three dimensional partonic structure of hadrons and their spin decomposition, for non-zero skewness within the AdS/QCD formalism. To this aim the canonical scheme to calculate GPDs at zero skewness has been properly generalized. Furthermore, we show that the latter quantities, in this non-forward regime, are sensitive to non-trivial details of the hadronic light front wave function, such as a kind of parton correlations usually not accessible in studies of form factors and GPDs at zero skewness.
Determination of neutron fracture functions from a global QCD analysis of the leading neutron production at HERA
Shoeibi, Samira; Khanpour, Hamzeh; Taghavi-Shahri, F.; Javidan, Kurosh
In this article, we present our global QCD analysis of leading neutron production in deep inelastic scattering at H1 and ZEUS collaborations. The analysis is performed in the framework of a perturbative QCD description for semi-inclusive processes, which is based on the fracture functions approach. Modeling the nonperturbative part of the fragmentation process at the input scale Q02, we analyze the Q2 dependence of the leading neutron structure functions and obtain the neutron fracture functions (neutron FFs) from next-to-leading order global QCD fit to data. We have also performed a careful estimation of the uncertainties using the "Hessian method" for the neutron FFs and corresponding observables originating from experimental errors. The predictions based on the obtained neutron FFs are in good agreement with all data analyzed, at small and large longitudinal momentum fraction xL as well as the scaled fractional momentum variable β .
Exploring Nf=2 +1 QCD thermodynamics from the gradient flow
Taniguchi, Yusuke; Ejiri, Shinji; Iwami, Ryo; Kanaya, Kazuyuki; Kitazawa, Masakiyo; Suzuki, Hiroshi; Umeda, Takashi; Wakabayashi, Naoki; WHOT-QCD Collaboration
The energy-momentum tensor plays an important role in QCD thermodynamics. Its expectation value contains information of the pressure and the energy density as its diagonal part. Further properties like viscosity and specific heat can be extracted from its correlation function. A nonperturbative evaluation of it on the lattice is called. Recently, a new method based on the gradient flow was introduced to calculate the energy-momentum tensor on the lattice and has been successfully applied to quenched QCD. In this paper, we apply the gradient flow method to calculate the energy-momentum tensor in (2 +1 )-flavor QCD adopting a nonperturbatively O (a )-improved Wilson quark action and the renormalization group-improved Iwasaki gauge action. As the first application of the method with dynamical quarks, we study at a single but fine lattice spacing a ≃0.07 fm with heavy u and d quarks (mπ/mρ≃0.63 ) and approximately physical s quark (mηss/mϕ≃0.74 ). With the fixed-scale approach, temperature is varied by the temporal lattice size Nt at a fixed lattice spacing. Performing simulations on lattices with Nt=16 to 4, the temperature range of T ≃174 - 697 MeV is covered. We find that the results of the pressure and the energy density by the gradient flow method are consistent with the previous results using the T -integration method at T ≲280 MeV (Nt≳10 ), while the results show disagreement at T ≳350 MeV (Nt≲8 ), presumably due to the small-Nt lattice artifact of O ((a T )2) =O (1 /Nt2) . We also apply the gradient flow method to evaluate the chiral condensate taking advantage of the gradient flow method that renormalized quantities can be directly computed avoiding the difficulty of explicit chiral violation with lattice quarks. We compute the renormalized chiral condensate in the MS ¯ scheme at renormalization scale μ =2 GeV with a high precision to study the temperature dependence of the chiral condensate and its disconnected susceptibility. Even with
Nuclear physics from strong coupling QCD
Fromm, Michael
The strong coupling limit (beta_gauge = 0) of QCD offers a number of remarkable research possibilities, of course at the price of large lattice artifacts. Here, we determine the complete phase diagram as a function of temperature T and baryon chemical potential mu_B, for one flavor of staggered fermions in the chiral limit, with emphasis on the determination of a tricritical point and on the T ~ 0 transition to nuclear matter. The latter is known to happen for mu_B substantially below the baryon mass, indicating strong nuclear interactions in QCD at infinite gauge coupling. This leads us to studying the properties of nuclear matter from first principles. We determine the nucleon-nucleon potential in the strong coupling limit, as well as masses m_A of nuclei as a function of their atomic number A. Finally, we clarify the origin of nuclear interactions at strong coupling, which turns out to be a steric effect.
Probing QCD and new physics with dijets
CERN. Geneva
Dijets are the most abundant final state in hadron collisions. During the last 30 years dijets have been used to probe QCD and also search for new phenomena beyond the Standard Model. Recent results from Tevatron and LHC are discussed that reveal the full physics potential of dijets. Precise measurements of cross sections and angular observables, made possible thanks to the excellent understanding of the jet objects, confront the perturbative QCD predictions at the multi-TeV regime and constrain the PDFs. At the same time, the dijet invariant mass spectrum is used as a means of searching for resonances and for contact interactions between the quarks. Following the success of the LHC Run I physics program, dijets will once again play a central role in the quest for exciting discoveries at Run II, and we are prepared to exploit this powerful final state.
A Boltzmann Equation for the QCD Plasma
Blaizot, Jean-Paul; Blaizot, Jean-Paul; Iancu, Edmond
We present a derivation of a Boltzmann equation for the QCD plasma, starting from the quantum field equations. The derivation is based on a gauge covariant gradient expansion which takes consistently into account all possible dependences on the gauge coupling assumed to be small. We point out a limitation of the gradient expansion arising when the range of the interactions becomes comparable with that of the space-time inhomogeneities of the system. The method is first applied to the case of scalar electrodynamics, and then to the description of long wavelength colour fluctuations in the QCD plasma, where our equation coincides with that recently proposed by Arnold, Son and Yaffe. We discuss interesting cancellations among various collision terms, which occur in the calculation of most transport coefficients, but not in that of the quasiparticle lifetime, or in that of the relaxation time of colour excitations.
Disentangling running coupling and conformal effects in QCD
Brodsky, S J; Grunberg, G; Rathsman, J
We investigate the relation between a postulated skeleton expansion and the conformal limit of QCD. We begin by developing some consequences of an Abelian-like skeleton expansion, which allows one to disentangle running-coupling effects from the remaining skeleton coefficients. The latter are by construction renormalon free, and hence hopefully better behaved. We consider a simple ansatz for the expansion, where an observable is written as a sum of integrals over the running coupling. We show that in this framework one can set a unique Brodsky-Lepage-Mackenzie (BLM) scale-setting procedure as an approximation to the running-coupling integrals, where the BLM coefficients coincide with the skeleton ones. Alternatively, the running-coupling integrals can be approximated using the effective charge method. We discuss the limitations in disentangling running coupling effects in the absence of a diagrammatic construction of the skeleton expansion. Independently of the assumed skeleton structure we show that BLM coef...
Moments of nucleon generalized parton distributions from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Alexandrou, C. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center; Carbonell, J.; Harraud, P.A.; Papinutto, M. [UJF/CNRS/IN2P3, Grenoble (France). Lab. de Physique Subatomique et Cosmologie; Constantinou, M.; Kallidonis, C. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Guichon, P. [CEA-Saclay, Gif-sur-Yvette (France). IRFU-Service de Physique Nucleaire; Jansen, K. [DESY, Zeuthen (Germany). NIC; Korzec, T. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Humboldt Univ. Berlin (Germany). Inst. fuer Physik
We present results on the lower moments of the nucleon generalized parton distributions within lattice QCD using two dynamical flavors of degenerate twisted mass fermions. Our simulations are performed on lattices with three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm, allowing the investigation of cut-off effects. The volume dependence is examined using simulations on two lattices of spatial length L=2.1 fm and L=2.8 fm. The simulations span pion masses in the range of 260-470 MeV. Our results are renormalized nonperturbatively and the values are given in the MS scheme at a scale {mu}=2 GeV. They are chirally extrapolated to the physical point in order to compare with experiment. The consequences of these results on the spin carried by the quarks in the nucleon are investigated. (orig.)
Asymmetric dark matter and the hadronic spectra of hidden QCD
Lonsdale, Stephen J.; Schroor, Martine; Volkas, Raymond R.
The idea that dark matter may be a composite state of a hidden non-Abelian gauge sector has received great attention in recent years. Frameworks such as asymmetric dark matter motivate the idea that dark matter may have similar mass to the proton, while mirror matter and G ×G grand unified theories provide rationales for additional gauge sectors which may have minimal interactions with standard model particles. In this work we explore the hadronic spectra that these dark QCD models can allow. The effects of the number of light colored particles and the value of the confinement scale on the lightest stable state, the dark matter candidate, are examined in the hyperspherical constituent quark model for baryonic and mesonic states.
Perturbative QCD versus pion exchange and hadronic FSI effects in the γγ→ π+π- reaction
Szczurek, A.; Speth, J.
The interplay of pQCD, pion exchange and FSI effects is studied for the γγ→ π+π- reaction in the region of 2 GeV < Wγγ< 6 GeV. We find strong interference effects between pQCD and soft pion-exchange amplitudes up to Wγγ˜ 4 GeV. We discuss to which extend the conventional hadronic FSI effects could cloud the pQCD effects. We study multiple soft and hard scattering effects as well as the coupling between final state hadronic channels. We show how the perturbative effects in γγ→ ρρ may mix with perturbative effects in γγ→ π+π-. The effects discussed in this paper improve the agreement with the new data of the DELPHI and ALEPH Collaborations. We give estimates of the onset of the pQCD regime. Predictions for γγ→ π0π0 are presented.
Applications Of Chiral Perturbation Theory To Lattice Qcd
Van de Water, R S
Quantum chromodynamics (QCD) is the fundamental theory that describes the interaction of quarks and gluons. Thus, in principle, one should be able to calculate all properties of hadrons from the QCD Lagrangian. It turns out, however, that such calculations can only be performed numerically on a computer using the nonperturbative method of lattice QCD, in which QCD is simulated on a discrete spacetime grid. Because lattice simulations use unphysically heavy quark masses (for computational reasons), lattice results must be connected to the real world using expressions calculated in chiral perturbation theory (χPT), the low-energy effective theory of QCD. Moreover, because real spacetime is continuous, they must be extrapolated to the continuum using an extension of χPT that includes lattice discretization effects, such as staggered χPT. This thesis is organized as follows. We motivate the need for lattice QCD and present the basic methodology in Chapter 1. We describe a common approximat...
Calculation of weak transitions in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Brower, R.C.; Maturana, G.; Gavela, M.B.; Gupta, R.
We propose the use of Monte Carlo simulations of QCD to evaluate hadronic matrix elements of local operators encountered in electroweak and grand-unified-theory transitions. Preliminary Monte Carlo estimates are made of the ..delta..S = 2 matrix elements responsible for the K/sub l/-K/sub S/ mass difference and the ..delta..S = 1 operators believed to explain the ..delta..I = (1/2) enhancement.
Energy Technology Data Exchange (ETDEWEB)
S.R. Beane; U. van Kolck
We show that existing data suggest a simple scenario in which the nucleon and the Delta and Roper resonances act as chiral partners in a reducible representation of the full QCD chiral symmetry group. We discuss the peculiar interpretation of this scenario using spin-flavour symmetries of the naive constituent quark model, as well as the consistency of the scenario with large-Nc expectations.
Ab initio Hadron structure from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
J.D. Bratt; R.G. Edwards; M. Engelhardt; G.T. Fleming; Ph. Hägler; B. Musch; J.W. Negele; K. Orginos; A.V. Pochinsky; D.B. Renner; D.G. Richards; W. Schroers
Early scattering experiments revealed that the proton was not a point particle but a bound state of many quarks and gluons. Deep inelastic scattering (DIS) experiments have accurately determined the probability of struck quarks carrying a fraction of the proton's momentum. The current generation of experiments and Lattice QCD calculations will provide detailed multi-dimensional pictures of the distributions of quarks and gluons inside the proton.
Nucleon and delta masses in QCD
Rafecas López, María Magdalena; Vento Torres, Vicente
Using the positivity of the path integral measure of $QCD$ and defining a structure for the quark propagator in a background field according to the fluxon scenario for confinement, we calculate and compare the correlators for nucleon and delta. From their shape we elucidate about the origin of their mass difference, which in our simplified scenario is due to the tensor structure in the propagator. This term arises due to a dynamical mechanism which is responsible simultaneously for confinemen...
Parton energy loss in QCD matter
Tywoniuk, Konrad
QCD jets, produced copiously in heavy-ion collisions at LHC and also at RHIC, serve as probes of the dynamics of the quark-gluon plasma (QGP). Jet fragmentation in the medium is interesting in its own right and, in order to extract pertinent information about the QGP, it has to be well understood. We present a brief overview of the physics involved and argue that jet substructure observables provide new opportunities for understanding the nature of the modifications.
Meson Correlators in Finite Temperature Lattice QCD
De Forcrand, Philippe; Hashimoto, T; Hioki, S; Matsufuru, H; Miyamura, O; Nakamura, A; Takaishi, T; Umeda, T; Stamatescu, I O; CERN. Geneva; Forcrand, Ph. de
We analyze temporal and spatial meson correlators in quenched lattice QCD at T>0. Below T_c we observe little change in the meson properties as compared with T=0. Above T_c we observe new features: chiral symmetry restoration and signals of plasma formation, but also indication of persisting mesonic (metastable) states and different temporal and spatial masses in the mesonic channels. This suggests a complex picture of QGP in the region 1 - 1.5 T_c.
Energy- and cost-efficient lattice-QCD computations using graphics processing units
Energy Technology Data Exchange (ETDEWEB)
Bach, Matthias
Quarks and gluons are the building blocks of all hadronic matter, like protons and neutrons. Their interaction is described by Quantum Chromodynamics (QCD), a theory under test by large scale experiments like the Large Hadron Collider (LHC) at CERN and in the future at the Facility for Antiproton and Ion Research (FAIR) at GSI. However, perturbative methods can only be applied to QCD for high energies. Studies from first principles are possible via a discretization onto an Euclidean space-time grid. This discretization of QCD is called Lattice QCD (LQCD) and is the only ab-initio option outside of the high-energy regime. LQCD is extremely compute and memory intensive. In particular, it is by definition always bandwidth limited. Thus - despite the complexity of LQCD applications - it led to the development of several specialized compute platforms and influenced the development of others. However, in recent years General-Purpose computation on Graphics Processing Units (GPGPU) came up as a new means for parallel computing. Contrary to machines traditionally used for LQCD, graphics processing units (GPUs) are a massmarket product. This promises advantages in both the pace at which higher-performing hardware becomes available and its price. CL2QCD is an OpenCL based implementation of LQCD using Wilson fermions that was developed within this thesis. It operates on GPUs by all major vendors as well as on central processing units (CPUs). On the AMD Radeon HD 7970 it provides the fastest double-precision D kernel for a single GPU, achieving 120GFLOPS. D - the most compute intensive kernel in LQCD simulations - is commonly used to compare LQCD platforms. This performance is enabled by an in-depth analysis of optimization techniques for bandwidth-limited codes on GPUs. Further, analysis of the communication between GPU and CPU, as well as between multiple GPUs, enables high-performance Krylov space solvers and linear scaling to multiple GPUs within a single system. LQCD
Energy Technology Data Exchange (ETDEWEB)
Karami, K.; Abdolmaleki, A.; Asadzadeh, S. [University of Kurdistan, Department of Physics, Sanandaj (Iran, Islamic Republic of); Safari, Z. [Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of)
Within the framework of modified teleparallel gravity, we reconstruct a f(T) model corresponding to the QCD ghost dark energy scenario. For a spatially flat FRW universe containing only the pressureless matter, we obtain the time evolution of the torsion scalar T (or the Hubble parameter). Then, we calculate the effective torsion equation of state parameter of the QCD ghost f(T)-gravity model as well as the deceleration parameter of the universe. Furthermore, we fit the model parameters by using the latest observational data including SNeIa, CMB and BAO data. We also check the viability of our model using a cosmographic analysis approach. Moreover, we investigate the validity of the generalized second law (GSL) of gravitational thermodynamics for our model. Finally, we point out the growth rate of matter density perturbation. We conclude that in QCD ghost f(T)-gravity model, the universe begins a matter dominated phase and approaches a de Sitter regime at late times, as expected. Also this model is consistent with current data, passes the cosmographic test, satisfies the GSL and fits the data of the growth factor well as the {Lambda}CDM model. (orig.)
QCD, Tevatron results and LHC prospects
Energy Technology Data Exchange (ETDEWEB)
Elvira, V.Daniel; /Fermilab
We present a summary of the most recent measurements relevant to Quantum Chromodynamics (QCD) delivered by the D0 and CDF Tevatron experiments by May 2008. CDF and D0 are moving toward precision measurements of QCD based on data samples in excess of 1 fb-1. The inclusive jet cross sections have been extended to forward rapidity regions and measured with unprecedented precision following improvements in the jet energy calibration. Results on dijet mass distributions, bbbar dijet production using tracker based triggers, underlying event in dijet and Drell-Yan samples, inclusive photon and diphoton cross sections complete the list of measurements included in this paper. Good agreement with pQCD within errors is observed for jet production measurements. An improved and consistent theoretical description is needed for photon+jets processes. Collisions at the LHC are scheduled for early fall 2008, opening an era of discoveries at the new energy frontier, 5-7 times higher than that of the Tevatron.
Chiral symmetry breakings in supersymmetric QCD
Energy Technology Data Exchange (ETDEWEB)
Shinmura, Mamoru; Yamawaki, Koichi (Nagoya Univ. (Japan). Dept. of Physics)
It is argued that spontaneous chiral symmetry breaking in supersymmetric QCD is due to the boson pair condensation
ALEPH Tau Spectral Functions and QCD
Davier, M; Zhang, Z; Davier, Michel; Hoecker, Andreas; Zhang, Zhiqing
Hadronic $\\tau$ decays provide a clean laboratory for the precise study of quantum chromodynamics (QCD). Observables based on the spectral functions of hadronic $\\tau$ decays can be related to QCD quark-level calculations to determine fundamental quantities like the strong coupling constant, quark and gluon condensates. Using the ALEPH spectral functions and branching ratios, complemented by some other available measurements, and a revisited analysis of the theoretical framework, the value $\\asm = 0.345 \\pm 0.004_{\\rm exp} \\pm 0.009_{\\rm th}$ is obtained. Taken together with the determination of \\asZ from the global electroweak fit, this result leads to the most accurate test of asymptotic freedom: the value of the logarithmic slope of $\\alpha_s^{-1}(s)$ is found to agree with QCD at a precision of 4%. The value of \\asZ obtained from $\\tau$ decays is $\\asZ = 0.1215 \\pm 0.0004_{\\rm exp} \\pm 0.0010_{\\rm th} \\pm 0.0005_{\\rm evol} = 0.1215 \\pm 0.0012$.
Aguilar-Saavedra, J. A.; Collins, Jack; Mishra, Rashmish K.
New particles beyond the Standard Model might be produced with a very high boost, for instance if they result from the decay of a heavier particle. If the former decay hadronically, then their signature is a single massive fat jet which is difficult to separate from QCD backgrounds. Jet substructure and machine learning techniques allow for the discrimination of many specific boosted objects from QCD, but the scope of possibilities is very large, and a suite of dedicated taggers may not be able to cover every possibility — in addition to making experimental searches cumbersome. In this paper we describe a generic model-independent tagger that is able to discriminate a wide variety of hadronic boosted objects from QCD jets using N -subjettiness variables, with a significance improvement varying between 2 and 8. This is in addition to any improvement that might come from a cut on jet mass. Such a tagger can be used in model-independent searches for new physics yielding fat jets. We also show how such a tagger can be applied to signatures over a wide range of jet masses without sculpting the background distributions, allowing to search for new physics as bumps on jet mass distributions.
QCD in heavy quark production and decay
Energy Technology Data Exchange (ETDEWEB)
Wiss, J. [Univ. of Illinois, Urbana, IL (United States)
The author discusses how QCD is used to understand the physics of heavy quark production and decay dynamics. His discussion of production dynamics primarily concentrates on charm photoproduction data which are compared to perturbative QCD calculations which incorporate fragmentation effects. He begins his discussion of heavy quark decay by reviewing data on charm and beauty lifetimes. Present data on fully leptonic and semileptonic charm decay are then reviewed. Measurements of the hadronic weak current form factors are compared to the nonperturbative QCD-based predictions of Lattice Gauge Theories. He next discusses polarization phenomena present in charmed baryon decay. Heavy Quark Effective Theory predicts that the daughter baryon will recoil from the charmed parent with nearly 100% left-handed polarization, which is in excellent agreement with present data. He concludes by discussing nonleptonic charm decay which is traditionally analyzed in a factorization framework applicable to two-body and quasi-two-body nonleptonic decays. This discussion emphasizes the important role of final state interactions in influencing both the observed decay width of various two-body final states as well as modifying the interference between interfering resonance channels which contribute to specific multibody decays. 50 refs., 77 figs.
Qcd Sum Rule Analysis Of Baryon Masses
Liu, X
The masses of low-lying baryon states are calculated using the QCD sum rule method. Both octet and decuplet baryon states are studied via the conventional sum rule method and the new parity-projected sum rule method. Firstly, the low-lying N* channels of octets are studied via the conventional sum rule method. Using generalized interpolating fields, three independent sets of QCD sum rules are derived which allow the extraction of the spin 12± , and 32± states in both the non-strange and strange channels. Thereafter, we explored a new technique which exactly projects out the parities that are mixed in the conventional sum rules. One advantage of the new parity- project sum rules is to be able to study the origin of mass splittings between positive and negative-parity baryon pairs in a direct manner in relation to the chiral-symmetry breaking of QCD as manifested via the vacuum condensates. At last, we re-visited the spin 32± decuplet states in both the conventional and t...
Higgs boson gluon-fusion production in N3LO QCD
Anastasiou, Charalampos; Dulat, Falko; Herzog, Franz; Mistlberger, Bernhard
We present the cross-section for the production of a Higgs boson at hadron-colliders at next-to- next-to-next-to-leading order (N3LO) in perturbative QCD. The calculation is based on a method to perform a series expansion of the partonic cross-section around the threshold limit to an arbitrary order. We perform this expansion to sufficiently high order to obtain the value of the hadronic cross at N3LO in the large top-mass limit. For renormalisation and factorisation scales equal to half the Higgs mass, the N3LO corrections are of the order of +2.2%. The total scale variation at N3LO is 3%, reducing the uncertainty due to missing higher order QCD corrections by a factor of three.
Theoretical overview: Hot and dense QCD in equilibrium
Energy Technology Data Exchange (ETDEWEB)
Hatsuda, Tetsuo
Static and dynamical properties of QCD at finite temperature and density are reviewed. Non-perturbative aspects of the QCD plasma and modification of the hadron properties associated with the chiral transition are discussed on the basis of lattice data, effective theories and QCD sum rules. Special emphasis is laid on the importance of the finite baryon density to see the effects of the restoration of chiral symmetry in experiment.
Transition to perturbative QCD in two-photon collisions
Hsieh, Ron-Chou; Li, Hsiang-nan
We propose that the different angular distributions in two-photon collisions observed at low and high center-of-mass energies $W_{\\gamma\\gamma}$ indicate the transition from nonperturbative to perturbative QCD. We calculate the differential cross sections of $\\gamma \\gamma\\to\\pi \\pi$, $KK$ in the angle $\\theta$ of one of the final-state mesons using QCD sum rules and the perturbative QCD approach based on $k_T$ factorization theorem. Our predictions from sum rules (perturbative QCD) decrease ...
QCD and Light-Front Holography
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Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; de Teramond, Guy F.; /Costa Rica U.
The soft-wall AdS/QCD model, modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics. The model predicts a zero-mass pion for zero-mass quarks and a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number N. Light-Front Holography maps the amplitudes which are functions of the fifth dimension variable z of anti-de Sitter space to a corresponding hadron theory quantized on the light front. The resulting Lorentz-invariant relativistic light-front wave equations are functions of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. The result is to a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryon light-quark bound states, which in turn predict the behavior of the pion and nucleon form factors. The theory implements chiral symmetry in a novel way: the effects of chiral symmetry breaking increase as one goes toward large interquark separation, consistent with spectroscopic data, and the the hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. The soft-wall model also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q) and its {beta}-function which agrees with the effective coupling {alpha}{sub g1} extracted from the Bjorken sum rule. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms. A new perspective on quark and gluon condensates is also reviewed.
Hard probes in heavy ion collisions at the LHC: PDFs, shadowing and $pA$ collisions
Accardi, Alberto; Botje, M.; Brodsky, S.J.; Cole, B.; Eskola, K.J.; Fai, George I.; Frankfurt, L.; Fries, R.J.; Geist, Walter M.; Guzey, V.; Honkanen, H.; Kolhinen, V.J.; Kovchegov, Yu.V.; McDermott, M.; Morsch, A.; Qiu, Jian-wei; Salgado, C.A.; Strikman, M.; Takai, H.; Tapprogge, S.; Vogt, R.; Zhang, X.f.
This manuscript is the outcome of the subgroup ``PDFs, shadowing and $pA$ collisions'' from the CERN workshop ``Hard Probes in Heavy Ion Collisions at the LHC''. In addition to the experimental parameters for $pA$ collisions at the LHC, the issues discussed are factorization in nuclear collisions, nuclear parton distributions (nPDFs), hard probes as the benchmark tests of factorization in $pA$ collisions at the LHC, and semi-hard probes as observables with potentially large nuclear effects. Also, novel QCD phenomena in $pA$ collisions at the LHC are considered. The importance of the $pA$ program at the LHC is emphasized.
Physics of the 1 Teraflop RIKEN-BNL-Columbia QCD project. Proceedings of RIKEN BNL Research Center workshop: Volume 13
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A workshop was held at the RIKEN-BNL Research Center on October 16, 1998, as part of the first anniversary celebration for the center. This meeting brought together the physicists from RIKEN-BNL, BNL and Columbia who are using the QCDSP (Quantum Chromodynamics on Digital Signal Processors) computer at the RIKEN-BNL Research Center for studies of QCD. Many of the talks in the workshop were devoted to domain wall fermions, a discretization of the continuum description of fermions which preserves the global symmetries of the continuum, even at finite lattice spacing. This formulation has been the subject of analytic investigation for some time and has reached the stage where large-scale simulations in QCD seem very promising. With the computational power available from the QCDSP computers, scientists are looking forward to an exciting time for numerical simulations of QCD.
Thermodynamic hardness and the maximum hardness principle
Franco-Pérez, Marco; Gázquez, José L.; Ayers, Paul W.; Vela, Alberto
An alternative definition of hardness (called the thermodynamic hardness) within the grand canonical ensemble formalism is proposed in terms of the partial derivative of the electronic chemical potential with respect to the thermodynamic chemical potential of the reservoir, keeping the temperature and the external potential constant. This temperature dependent definition may be interpreted as a measure of the propensity of a system to go through a charge transfer process when it interacts with other species, and thus it keeps the philosophy of the original definition. When the derivative is expressed in terms of the three-state ensemble model, in the regime of low temperatures and up to temperatures of chemical interest, one finds that for zero fractional charge, the thermodynamic hardness is proportional to T-1(I -A ) , where I is the first ionization potential, A is the electron affinity, and T is the temperature. However, the thermodynamic hardness is nearly zero when the fractional charge is different from zero. Thus, through the present definition, one avoids the presence of the Dirac delta function. We show that the chemical hardness defined in this way provides meaningful and discernible information about the hardness properties of a chemical species exhibiting integer or a fractional average number of electrons, and this analysis allowed us to establish a link between the maximum possible value of the hardness here defined, with the minimum softness principle, showing that both principles are related to minimum fractional charge and maximum stability conditions.
Strong coupling constant from Adler function in lattice QCD
Hudspith, Renwick J.; Lewis, Randy; Maltman, Kim; Shintani, Eigo
We compute the QCD coupling constant, αs, from the Adler function with vector hadronic vacuum polarization (HVP) function. On the lattice, Adler function can be measured by the differential of HVP at two different momentum scales. HVP is measured from the conserved-local vector current correlator using nf = 2 + 1 flavor Domain Wall lattice data with three different lattice cutoffs, up to a-1 ≈ 3.14 GeV. To avoid the lattice artifact due to O(4) symmetry breaking, we set the cylinder cut on the lattice momentum with reflection projection onto vector current correlator, and it then provides smooth function of momentum scale for extracted HVP. We present a global fit of the lattice data at a justified momentum scale with three lattice cutoffs using continuum perturbation theory at 𝒪(αs4) to obtain the coupling in the continuum limit at arbitrary scale. We take the running to Z boson mass through the appropriate thresholds, and obtain αs(5)(MZ) = 0.1191(24)(37) where the first is statistical error and the second is systematic one.
Hocker, Andreas
We present new results for the r hadronic spectral functions analysis using data accumulated by the ALEPH detector at LEP during the years 1991-94. The vector and the axial-vector spectral functions are determined from their respective unfolded, i.e., physical invariant mass spectra. The r vector and axial-vector hadronic widths and certain spectral moments are exploited to measure a, and nonperturbative contributions at the r mass scale. The best, and experimentally and theoretically most robust, determination of a,(Mr) is obtained from the inclusive (V + A) fit that yields a,(Mr) = 0.349 ± 0.018 giving a,(Mz) = 0.1 212 ± 0.0022 after the evolution to the mass of the Z boson. The approach of the Operator Product Expansion (OPE) is tested experimentally by means of an evolution of the r hadronic width to masses smaller than the r mass.
Weak transitions in lattice QCD
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Maturana, G.
Some techniques to calculate the effects of the strong interactions on the matrix elements of weak processes are described. The lattice formulation of Quantum Chromodynamics is used to account for the low energy gluons, and the corresponding numerical methods are explained. The high energy contributions are included in effective lagrangians and the problem of matching the different scales related to the renormalization of the operators and wavefunctions is also discussed. The ..delta..l = 1/2 enhancement rule and the K/sup 0/-anti-K/sup 0/ are used to illustrate these techniques and the results of a numerical calculation is reported. The values obtained are very encouraging and they certainly show good qualitative agreement with the experimental values. The emphasis is on general techniques, and in particular, several improvements to this particular calculation are proposed.
NLO QCD corrections to off-shell top-antitop production with leptonic decays in association with a Higgs boson at the LHC
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Denner, Ansgar; Feger, Robert [Universität Würzburg, Institut für Theoretische Physik und Astrophysik, Emil-Hilb-Weg 22, 97074 Würzburg (Germany)
We compute the hadronic production of top-antitop pairs in association with a Higgs boson at next-to-leading-order QCD, including the decay of the top and antitop quark into bottom quarks and leptons. Our computation is based on full leading and next-to-leading-order matrix elements for e{sup +}ν{sub e}μ{sup −}ν̄{sub μ}bb̄H(j) and includes all non-resonant contributions, off-shell effects and interferences. Numerical results for the integrated cross section and several differential distributions are given for the LHC operating at 13 TeV using a fixed and a dynamical factorization and renormalization scale. The use of the dynamical instead of the fixed scale improves the perturbative stability in high-energy tails of most distributions, while the integrated cross section is hardly affected differing by only about one per cent and leading to almost the same K factor of about 1.17.
Chiral symmetry breaking in QCD with two light flavors.
Engel, Georg P; Giusti, Leonardo; Lottini, Stefano; Sommer, Rainer
A distinctive feature of the presence of spontaneous chiral symmetry breaking in QCD is the condensation of low modes of the Dirac operator near the origin. The rate of condensation must be equal to the slope of M(π)(2)F(π)(2)/2 with respect to the quark mass m in the chiral limit, where M(π) and F(π) are the mass and the decay constant of the Nambu-Goldstone bosons. We compute the spectral density of the (Hermitian) Dirac operator, the quark mass, the pseudoscalar meson mass, and decay constant by numerical simulations of lattice QCD with two light degenerate Wilson quarks. We use lattices generated by the Coordinated Lattice Simulation (CLS) group at three values of the lattice spacing in the range 0.05-0.08 fm, and for several quark masses corresponding to pseudoscalar mesons masses down to 190 MeV. Thanks to this coverage of parameters space, we can extrapolate all quantities to the chiral and continuum limits with confidence. The results show that the low quark modes do condense in the continuum as expected by the Banks-Casher mechanism, and the rate of condensation agrees with the Gell-Mann-Oakes-Renner relation. For the renormalization-group-invariant ratios we obtain [Σ(RGI)](1/3)/F=2.77(2)(4) and Λ(M̅S)/F=3.6(2), which correspond to [Σ(M̅S)(2 GeV)](1/3)=263(3)(4) MeV and F=85.8(7)(20) MeV if F(K) is used to set the scale by supplementing the theory with a quenched strange quark.
AdS/CFT and Exclusive Processes in QCD
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; de Teramond, Guy F.
The AdS/CFT correspondence between string theory in AdS space and conformal field theories in physical space-time leads to an analytic, semi-classical model for strongly-coupled QCD which has scale invariance and dimensional counting at short distances and color confinement at large distances. One can use holography to map the amplitude describing the hadronic state in the fifth dimension of Anti-de Sitter space AdS5 to the light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons in QCD at the amplitude level. In particular, we show that there is an exact correspondence between the fifth-dimensional coordinate of AdS space z and a specific impact variable {var_sigma} which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time. New relativistic light-front equations in ordinary space-time can then be derived which reproduce the results obtained using the 5-dimensional theory. The effective light-front equations possess elegant algebraic structures and integrability properties. This connection between the AdS and the light-front representations allows one to compute the analytic form of the frame-independent light-front wavefunctions, the fundamental entities which encode hadron properties and allow the computation of decay constants, form factors, deeply virtual Compton scattering, exclusive heavy hadron decays and other exclusive scattering amplitudes. As specific examples we compute the pion coupling constant f{sub {pi}} and study the behavior of the pion form factor F{sub {pi}}(q{sup 2}) in the space and time-like regions. We also determine the Dirac nucleon form factors F{sup p}{sub 1}(q{sup 2}) and F{sup n}{sub 1} (q{sup 2}) in the space-like region.
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; de Teramond, Guy F.
The AdS/CFT correspondence between string theory in AdS space and conformal field theories in physical space-time leads to an analytic, semi-classical model for strongly-coupled QCD which has scale invariance and dimensional counting at short distances and color confinement at large distances. The AdS/CFT correspondence also provides insights into the inherently nonperturbative aspects of QCD such as the orbital and radial spectra of hadrons and the form of hadronic wavefunctions. In particular, we show that there is an exact correspondence between the fifth-dimensional coordinate of AdS space z and a specific impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time. This connection leads to AdS/CFT predictions for the analytic form of the frame-independent light-front wavefunctions (LFWFs) of mesons and baryons, the fundamental entities which encode hadron properties. The LFWFs in turn predict decay constants and spin correlations, as well as dynamical quantities such as form factors, structure functions, generalized parton distributions, and exclusive scattering amplitudes. Relativistic light-front equations in ordinary space-time are found which reproduce the results obtained using the fifth-dimensional theory and have remarkable algebraic structures and integrability properties. As specific examples we describe the behavior of the pion form factor in the space and time-like regions and determine the Dirac nucleon form factors in the space-like region. An extension to nonzero quark mass is used to determine hadronic distribution amplitudes of all mesons, heavy and light. We compare our results with the moments of the distribution amplitudes which have recently been computed from lattice gauge theory.
Industrial-scale application of Lactobacillus reuteri coupled with glycerol as a biopreservation system for inhibiting Clostridium tyrobutyricum in semi-hard ewe milk cheese.
Ávila, Marta; Gómez-Torres, Natalia; Delgado, David; Gaya, Pilar; Garde, Sonia
The suitability of the biopreservation system formed by reuterin-producing L. reuteri INIA P572 and glycerol (required for reuterin production) to prevent late blowing defect (LBD) was evaluated in industrial sized semi-hard ewe milk cheese contaminated with Clostridium tyrobutyricum INIA 68, a wild strain isolated from a LBD cheese. For this purpose, six batches of cheese were made (three with and three without clostridial spores): control cheeses with lactococci starter, cheeses with L. reuteri as adjunct, and cheeses with L. reuteri and 30 mM glycerol. Spores of C. tyrobutyricum INIA 68 germinated during pressing of cheese curd, causing butyric acid fermentation in cheese after 30 d of ripening. The addition of L. reuteri, without glycerol, enhanced the symptoms and the formation of volatile compounds associated with LBD. When glycerol was added to cheese milk contaminated with C. tyrobutyricum, L. reuteri was able to produce reuterin in cheese resulting in cheeses with a uniform cheese matrix and a volatile profile similar to cheese made with L. reuteri and glycerol (without spores). Accordingly, L. reuteri INIA P572 coupled with glycerol seems a novel biopreservation system to inhibit Clostridium growth and prevent LBD by means of in situ reuterin production. Copyright © 2017 Elsevier Ltd. All rights reserved.
Baryon interactions in lattice QCD: the direct method vs. the HAL QCD potential method
Iritani, Takumi
We make a detailed comparison between the direct method and the HAL QCD potential method for the baryon-baryon interactions, taking the $\\Xi\\Xi$ system at $m_\\pi= 0.51$ GeV in 2+1 flavor QCD and using both smeared and wall quark sources. The energy shift $\\Delta E_\\mathrm{eff}(t)$ in the direct method shows the strong dependence on the choice of quark source operators, which means that the results with either (or both) source are false. The time-dependent HAL QCD method, on the other hand, gives the quark source independent $\\Xi\\Xi$ potential, thanks to the derivative expansion of the potential, which absorbs the source dependence to the next leading order correction. The HAL QCD potential predicts the absence of the bound state in the $\\Xi\\Xi$($^1$S$_0$) channel at $m_\\pi= 0.51$ GeV, which is also confirmed by the volume dependence of finite volume energy from the potential. We also demonstrate that the origin of the fake plateau in the effective energy shift $\\Delta E_\\mathrm{eff}(t)$ at $t \\sim 1$ fm can b...
Communication: Generalizing Rosenfeld's excess-entropy scaling to predict long-time diffusivity in dense fluids of Brownian particles: from hard to ultrasoft interactions.
Pond, Mark J; Errington, Jeffrey R; Truskett, Thomas M
Computer simulations are used to test whether a recently introduced generalization of Rosenfeld's excess-entropy scaling method for estimating transport coefficients in systems obeying molecular dynamics can be extended to predict long-time diffusivities in fluids of particles undergoing Brownian dynamics in the absence of interparticle hydrodynamic forces. Model fluids with inverse-power-law, Gaussian-core, and Hertzian pair interactions are considered. Within the generalized Rosenfeld scaling method, long-time diffusivities of ultrasoft Gaussian-core and Hertzian particle fluids, which display anomalous trends with increasing density, are predicted (to within 20%) based on knowledge of interparticle interactions, excess entropy, and scaling behavior of simpler inverse-power-law fluids.
The impacts of low-cost treatment options upon scale formation potential in remote communities reliant on hard groundwaters. A case study: Northern Territory, Australia.
Kinsela, Andrew S; Jones, Adele M; Collins, Richard N; Waite, T David
The majority of small, remote communities within the Northern Territory (NT) in Central Australia are reliant on groundwater as their primary supply of domestic, potable water. Saturation indices for a variety of relevant minerals were calculated using available thermodynamic speciation codes on collected groundwater data across the NT. These saturation indices were used to assess the theoretical formation of problematic mineral-scale, which manifests itself by forming stubborn coatings on domestic appliances and fixtures. The results of this research show that 63% of the measured sites within the NT have the potential to form calcium carbonate (CaCO(3)) scale, increasing to 91% in arid, central regions. The data also suggests that all groundwaters are over-saturated with respect to amorphous calcium-bridged ferric-silica polymers, based on the crystalline mineral index (Ca(3)Fe(2)Si(3)O(12)), although the quantitative impact of this scale is limited by low iron concentrations. An assessment of possible low-cost/low-technology management options was made, including; lowering the temperature of hot-water systems, diluting groundwater with rainwater and modifying the pH of the source water. Source water pH modification (generally a reduction to pH 7.0) was shown to clearly alleviate potential carbonate-based scale formation, over and above the other two options, albeit at a greater technical and capital expense. Although low-cost/low-technology treatment options are unlikely to remove severe scale-related issues, their place in small, remote communities with minor scale problems should be investigated further, owing to the social, technical and capital barriers involved with installing advanced treatment plants (e.g. reverse osmosis) in such locations. Copyright © 2011 Elsevier B.V. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
With the operation of the RHIC heavy ion program, the theoretical understanding of QCD at finite temperature and density has become increasingly important. Though QCD at finite temperature has been extensively studied using lattice Monte-Carlo simulations over the past twenty years, most physical questions relevant for RHIC (and future) heavy ion experiments remain open. In lattice QCD at finite temperature and density there have been at least two major advances in recent years. First, for the first time calculations of real time quantities, like meson spectral functions have become available. Second, the lattice study of the QCD phase diagram and equation of state have been extended to finite baryon density by several groups. Both issues were extensively discussed in the course of the workshop. A real highlight was the study of the QCD phase diagram in (T, {mu})-plane by Z. Fodor and S. Katz and the determination of the critical end-point for the physical value of the pion mass. This was the first time such lattice calculations at, the physical pion mass have been performed. Results by Z Fodor and S. Katz were obtained using a multi-parameter re-weighting method. Other determinations of the critical end point were also presented, in particular using a Taylor expansion around {mu} = 0 (Bielefeld group, Ejiri et al.) and using analytic continuation from imaginary chemical potential (Ph. de Forcrand and O. Philipsen). The result based on Taylor expansion agrees within errors with the new prediction of Z. Fodor and S. Katz, while methods based on analytic continuation still predict a higher value for the critical baryon density. Most of the thermodynamics studies in full QCD (including those presented at this workshop) have been performed using quite coarse lattices, a = 0.2-0.3 fm. Therefore one may worry about cutoff effects in different thermodynamic quantities, like the transition temperature T{sub tr}. At the workshop U. Heller presented a study of the transition
Conjecture on the physical implications of the scale anomaly
Energy Technology Data Exchange (ETDEWEB)
Hill, Christopher T.; /Fermilab
Murray Gell-Mann, after co-inventing QCD, recognized the interplay of the scale anomaly, the renormalization group, and the origin of the strong scale, {Lambda}{sub QCD}. I tell a story, then elaborate this concept, and for the sake of discussion, propose a conjecture that the physical world is scale invariant in the classical, {h_bar}, limit. This principle has implications for the dimensionality of space-time, the cosmological constant, the weak scale, and Planck scale.
QCD with jets and photons at ATLAS and CMS
Barnovska-Blenessy, Zuzana; The ATLAS collaboration
A selection of recent QCD measurements by the ATLAS and CMS collaborations in final states with photons and jets is presented. New results with improved precision provide a probe of perturbative QCD, allowing to perform PDF fits and extracting the strong coupling constant $\\alpha_{S}$.
The QCD form factor of massive quarks and applications
Energy Technology Data Exchange (ETDEWEB)
Moch, S. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
We review the electromagnetic form factor of heavy quarks with emphasis on the QCD radiative corrections at two-loop order in the perturbative expansion. We discuss important properties of the heavy-quark form factor such as its exponentiation in the high-energy limit and its role in QCD factorization theorems for massive n-parton amplitudes. (orig.)
Volume independence in large Nc QCD-like gauge theories
Kovtun, Pavel; Ünsal, Mithat; Yaffe, Laurence G.
Volume independence in large Nc gauge theories may be viewed as a generalized orbifold equivalence. The reduction to zero volume (or Eguchi-Kawai reduction) is a special case of this equivalence. So is temperature independence in confining phases. A natural generalization concerns volume independence in ``theory space'' of quiver gauge theories. In pure Yang-Mills theory, the failure of volume independence for sufficiently small volumes (at weak coupling) due to spontaneous breaking of center symmetry, together with its validity above a critical size, nicely illustrate the symmetry realization conditions which are both necessary and sufficient for large Nc orbifold equivalence. The existence of a minimal size below which volume independence fails also applies to Yang-Mills theory with antisymmetric representation fermions [QCD(AS)]. However, in Yang-Mills theory with adjoint representation fermions [QCD(Adj)], endowed with periodic boundary conditions, volume independence remains valid down to arbitrarily small size. In sufficiently large volumes, QCD(Adj) and QCD(AS) have a large Nc ``orientifold'' equivalence, provided charge conjugation symmetry is unbroken in the latter theory. Therefore, via a combined orbifold-orientifold mapping, a well-defined large Nc equivalence exists between QCD(AS) in large, or infinite, volume and QCD(Adj) in arbitrarily small volume. Since asymptotically free gauge theories, such as QCD(Adj), are much easier to study (analytically or numerically) in small volume, this equivalence should allow greater understanding of large Nc QCD in infinite volume.
Massive pions, anomalies and baryons in holographic QCD
Energy Technology Data Exchange (ETDEWEB)
Domenech, O. [Departament de Fisica and IFAE, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain); Panico, G., E-mail: email@example.com [Institute for Theoretical Physics, ETH Zurich, 8093 Zurich (Switzerland); Wulzer, A. [Institut de Theorie des Phenomenes Physiques, EPFL, CH-1015 Lausanne (Switzerland)
We consider a holographic model of QCD, obtained by a very simple modification of the original construction, which describes at the same time the pion mass, the QCD anomalies and the baryons as topological solitons. We study in detail its phenomenological implications in both the mesonic and baryonic sectors and compare with the observations.
QCD on the BlueGene/L Supercomputer
Bhanot, G.; Chen, D.; Gara, A.; Sexton, J.; Vranas, P.
In June 2004 QCD was simulated for the first time at sustained speed exceeding 1 TeraFlops in the BlueGene/L supercomputer at the IBM T.J. Watson Research Lab. The implementation and performance of QCD in the BlueGene/L is presented.
Nonperturbative determination of the QCD potential at O(1/m)
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Koma, Y. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Koma, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Osaka Univ. (JP). Research Center for Nuclear Physics (RCNP); Wittig, H. [Mainz Univ. (Germany). Inst. fuer Physik
The relativistic correction to the QCD static inter-quark potential at O(1/m) is investigated nonperturbatively for the first time by using lattice Monte Carlo QCD simulations. The correction is found to be comparable with the Coulombic term of the static potential when applied to charmonium, and amounts to 26% of the Coulombic term for bottomonium. (Orig.)
Confinining properties of QCD in strong magnetic backgrounds
Directory of Open Access Journals (Sweden)
Bonati Claudio
Full Text Available Strong magnetic backgrounds are known to modify QCD properties at a nonperturbative level. We discuss recent lattice results, obtained for Nf = 2 + 1 QCD with physical quark masses, concerning in particular the modifications and the anisotropies induced at the level of the static quark-antiquark potential, both at zero and finite temperature.
Model for chiral symmetry breaking in QCD
Energy Technology Data Exchange (ETDEWEB)
Govaerts, J.; Weyers, J.; Mandula, J.E.
A recently proposed model for dynamical breaking of chiral symmetry in QCD is extended and developed for the calculation of pion and chiral symmetry breaking parameters. The pion is explicitly realized as a massless Goldstone boson and as a bound state of the constituent quarks. We compute, in the limit of exact chiral symmetry, Msub(Q), the constituent quark mass, fsub(..pi..), the pion decay coupling,
QCD simulations with staggered fermions on GPUs
Bonati, C.; Cossu, G.; D'Elia, M.; Incardona, P.
We report on our implementation of the RHMC algorithm for the simulation of lattice QCD with two staggered flavors on Graphics Processing Units, using the NVIDIA CUDA programming language. The main feature of our code is that the GPU is not used just as an accelerator, but instead the whole Molecular Dynamics trajectory is performed on it. After pointing out the main bottlenecks and how to circumvent them, we discuss the obtained performances. We present some preliminary results regarding OpenCL and multiGPU extensions of our code and discuss future perspectives.
The Feynman-Schwinger representation in QCD
Energy Technology Data Exchange (ETDEWEB)
Yu. A. Simonov; J.A. Tjon
The proper time path integral representation is derived explicitly for Green's functions in QCD. After an introductory analysis of perturbative properties, the total gluonic field is separated in a rigorous way into a nonperturbative background and valence gluon part. For nonperturbative contributions the background perturbation theory is used systematically, yielding two types of expansions,illustrated by direct physical applications. As an application, we discuss the collinear singularities in the Feynman-Schwinger representation formalism. Moreover, the generalization to nonzero temperature is made and expressions for partition functions in perturbation theory and nonperturbative background are explicitly written down.
Charmed Meson Scattering from Lattice QCD
Moir, Graham
State-of-the-art lattice QCD calculations of scattering amplitudes in coupled-channel $D\\pi$, $D\\eta$ and $D_{s}\\bar{K}$ scattering, as well elastic $DK$ scattering are discussed. The methodology employed allows a determination of the relevant poles in the scattering matrix, while also providing a measure of the coupling of each channel to a given pole. By investigating $S$, $P$ and $D$ wave interactions, the nature of states with $J^{P} = 0^{+}$, relevant for the $D^{*}_{0}(2400)$ and $D^{*}_{s0}(2317)$, as well as states with $J^{P} = 1^{-}, 2^{+}$ are discussed.
Dynamical gluon mass in QCD processes
Energy Technology Data Exchange (ETDEWEB)
Ducati, M.B. Gay; Sauter, W. [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Inst. de Fisica. Grupo de Fenomenologia de Particulas de Altas Energias (GFPAE)
We perform phenomenological applications of modified gluon propagators and running coupling constants in scattering processes in Quantum Chromodynamics (QCD). The modified forms of propagators and running coupling constant are obtained by non-perturbative methods. The processes investigated includes the diffractive ones - proton-proton elastic scattering, light vector meson photo-production and double vector meson production in gamma-gamma scattering - as well as the pion and kaon meson form factors. The results are compared with experimental data (if available), showing a good agreement with a gluon with dynamical mass but do not indicate the correct gluon propagator functional form. (author)
Solving QCD using multi-regge theory.
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White, A. R.
This talk outlines the derivation of a high-energy, transverse momentum cut-off, solution of QCD in which the Regge pole and ''single gluon'' properties of the pomeron are directly related to the confinement and chiral symmetry breaking properties of the hadron spectrum. In first approximation, the pomeron is a single reggeized gluon plus a ''wee parton'' component that compensates for the color and particle properties of the gluon. This solution corresponds to a supercritical phase of Reggeon Field Theory.
Algorithms for Disconnected Diagrams in Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Gambhir, Arjun Singh [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Stathopoulos, Andreas [College of William and Mary, Williamsburg, VA (United States); Orginos, Konstantinos [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Yoon, Boram [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gupta, Rajan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Syritsyn, Sergey [Stony Brook Univ., NY (United States)
Computing disconnected diagrams in Lattice QCD (operator insertion in a quark loop) entails the computationally demanding problem of taking the trace of the all to all quark propagator. We first outline the basic algorithm used to compute a quark loop as well as improvements to this method. Then, we motivate and introduce an algorithm based on the synergy between hierarchical probing and singular value deflation. We present results for the chiral condensate using a 2+1-flavor clover ensemble and compare estimates of the nucleon charges with the basic algorithm.
Nonlocal Condensate Model for QCD Sum Rules
Hsieh, Ron-Chou; Li, Hsiang-nan
We include effects of nonlocal quark condensates into QCD sum rules (QSR) via the K$\\ddot{\\mathrm{a}}$ll$\\acute{\\mathrm{e}}$n-Lehmann representation for a dressed fermion propagator, in which a negative spectral density function manifests their nonperturbative nature. Applying our formalism to the pion form factor as an example, QSR results are in good agreement with data for momentum transfer squared up to $Q^2 \\approx 10 $ GeV$^2$. It is observed that the nonlocal quark condensate contribut...
Effective Meson Field Theory from QCD
Hsieh, Ron-Chou
We give a simple and straightforward procedure of how to construct an effective meson Lagrangian from QCD Lagrangian. We integrate the methods of Gasser, Leutwyler, Alkofer and Reinhardt and use the derivative expansion scheme to derive the low energy effective Lagrangian for meson fields to $O(p^4)$. In this paper, why the meson particle can be treated as the goldstone mode is very clear. In our calculation the result in $O(p^2)$ is the same as in the chiral perturbation theory, but the resu...
Extracting Electric Polarizabilities from Lattice QCD
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Will Detmold, William Detmold, Brian Tiburzi, Andre Walker-Loud
Charged and neutral, pion and kaon electric polarizabilities are extracted from lattice QCD using an ensemble of anisotropic gauge configurations with dynamical clover fermions. We utilize classical background fields to access the polarizabilities from two-point correlation functions. Uniform background fields are achieved by quantizing the electric field strength with the proper treatment of boundary flux. These external fields, however, are implemented only in the valence quark sector. A novel method to extract charge particle polarizabilities is successfully demonstrated for the first time.
Nucleon wave function from lattice QCD
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Warkentin, Nikolaus
In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)
Perturbative and nonperturbative renormalization in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Institut fuer Theoretische Physik; Horsley, R. [University of Edinburgh (United Kingdom). School of Physics and Astronomy; Perlt, H. [Leipzig Univ. (DE). Institut fuer Theoretische Physik] (and others)
We investigate the perturbative and nonperturbative renormalization of composite operators in lattice QCD restricting ourselves to operators that are bilinear in the quark fields (quark-antiquark operators). These include operators which are relevant to the calculation of moments of hadronic structure functions. The nonperturbative computations are based on Monte Carlo simulations with two flavors of clover fermions and utilize the Rome-Southampton method also known as the RI-MOM scheme. We compare the results of this approach with various estimates from lattice perturbation theory, in particular with recent two-loop calculations. (orig.)
QCD fits to neutrino-iron structure functions at NuTeV
Energy Technology Data Exchange (ETDEWEB)
Radescu, Voica A. [Univ. of Pittsburgh, PA (United States)
This thesis presents a new determination of ΓQCD from Next-to-Leading Order QCD fits to the Q2 dependence of neutrino-iron structure functions. This is the first measurement of ΓQCD which uses a theoretical model that fully accounts for heavy quark production. Compared with previous neutrino measurements, the result has improved understanding of the largest systematic uncertainties on the muon and hadron energy scales. These improvements lead to one of the most precise determination of αS at moderate Q2. NuTeV is a neutrino-iron deep inelastic scattering (DIS) experiment that collected data during 1996-97 at Fermilab. The key features of NuTeV include its sign-selected beam which produced separate high purity neutrino and antineutrino beams, and its continuous calibration beam which enabled NuTeV to considerably improve the knowledge of energy scales which have dominated uncertainties in the previous measurements.
Distribution amplitudes of the {lambda}{sub b} baryon in QCD
Energy Technology Data Exchange (ETDEWEB)
Ball, Patricia [IPPP, Department of Physics, University of Durham, Durham DH1 3LE (United Kingdom); Physik-Department, Technische Universitaet Muenchen, D-85748 Garching (Germany)], E-mail: email@example.com; Braun, Vladimir M. [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg (Germany)], E-mail: firstname.lastname@example.com; Gardi, Einan [School of Physics, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom)], E-mail: email@example.com
The QCD description of exclusive decays of the {lambda}{sub b} baryon involves hadronic matrix elements of non-local light ray operators, the light-cone distribution amplitudes. We introduce the complete set of three-quark distribution amplitudes and calculate the renormalization scale dependence for the leading twist. At leading order in the strong coupling the evolution is driven by pairwise two-quark interactions: heavy-light involving Sudakov logarithms as in the B-meson case, and light-light as in light mesons. We solve the evolution equation and show that its main effect is to generate a radiative tail extending to high energies. Finally, we present simple models for the distribution amplitudes based on QCD sum rules, and study the effect of the evolution on these models.
Strong-Coupling Lattice QCD on Anisotropic Lattices arXiv
de Forcrand, Philippe; Vairinhos, Helvio
Anisotropic lattice spacings are mandatory to reach the high temperatures where chiral symmetry is restored in the strong coupling limit of lattice QCD. Here, we propose a simple criterion for the nonperturbative renormalisation of the anisotropy coupling $\\gamma$ in strongly-coupled SU($N$) or U($N$) lattice QCD with massless staggered fermions. We then compute the renormalised anisotropy $\\xi(\\gamma)$, and the strong-coupling analogue of Karsch's coefficients (the running anisotropy), for $N=3$. We achieve high precision by combining diagrammatic Monte Carlo and multi-histogram reweighting techniques. We observe that the mean field prediction in the continuous time limit captures the nonperturbative scaling, but receives a large, previously neglected correction on the unit prefactor. Using our nonperturbative prescription in place of the mean field result, we observe large corrections of the same magnitude to the continuous time limit of the static baryon mass, and of the location of the phase boundary asso...
Search for the QCD critical point in nuclear collisions at the CERN SPS
Anticic, T.; Barna, D.; Bartke, J.; Betev, L.; Bialkowska, H.; Blume, C.; Boimska, B.; Botje, M.; Bracinik, J.; Buncic, P.; Cerny, V.; Christakoglou, P.; Chung, P.; Chvala, O.; Cramer, J.G.; Dinkelaker, P.; Eckardt, V.; Fodor, Z.; Foka, P.; Friese, V.; Gazdzicki, M.; Genchev, V.; Grebieszkow, K.; Hohne, C.; Kadija, K.; Karev, A.; Kolesnikov, V.I.; Kowalski, M.; Kreps, M.; Laszlo, A.; Lacey, R.; van Leeuwen, M.; Lungwitz, B.; Makariev, M.; Malakhov, A.I.; Mateev, M.; Melkumov, G.L.; Mitrovski, M.; Mrowczynski, St.; Nicolic, V.; Palla, G.; Panagiotou, A.D.; Petridis, A.; Peryt, W.; Pikna, M.; Pluta, J.; Prindle, D.; Puhlhofer, F.; Renfordt, R.; Roland, C.; Roland, G.; Rybczynski, M.; Rybicki, A.; Sandoval, A.; Schmitz, N.; Schuster, T.; Seyboth, P.; Sikler, F.; Sitar, B.; Skrzypczak, E.; Slodkowski, M.; Stefanek, G.; Stock, R.; Strobele, H.; Susa, T.; Szuba, M.; Varga, D.; Vassiliou, M.; Veres, G.I.; Vesztergombi, G.; Vranic, D.; Wlodarczyk, Z.; Antoniou, N.G.; Diakonos, F.K.; Mavromanolakis, G.
Pion production in nuclear collisions at the SPS is investigated with the aim to search, in a restricted domain of the phase diagram, for power-laws in the behaviour of correlations which are compatible with critical QCD. We have analysed interactions of nuclei of different size (p+p, C+C, Si+Si, Pb+Pb) at 158A GeV adopting, as appropriate observables, scaled factorial moments in a search for intermittent fluctuations in transverse dimensions. The analysis is performed for $\\pi^+\\pi^-$ pairs with invariant mass very close to the two-pion threshold. In this sector one may capture critical fluctuations of the sigma component in a hadronic medium, even if the $\\sigma$-meson has no well defined vacuum state. Our results indicate the presence of power-law fluctuations in the freeze-out state of the Si+Si system approaching in size the prediction of critical QCD.
Search for QCD Instanton-Induced Processes at HERA in the High-$Q^2$ Domain
Andreev, Vladimir; Begzsuren, Khurelbaatar; Belousov, Anatoli; Bolz, Arthur; Boudry, Vincent; Brandt, Gerhard; Brisson, Violette; Britzger, Daniel; Buniatyan, Armen; Bylinkin, Alexander; Bystritskaya, Lena; Campbell, Alan; Cantun Avila, Karla~Beatriz; Cerny, Karel; Chekelian, Vladimir; Contreras, Guillermo; Cvach, Jaroslav; Dainton, John; Daum, Karin; Diaconu, Cristinel; Dobre, Monica; Dodonov, Vitaliy; Eckerlin, Guenter; Egli, Stephan; Elsen, Eckhard; Favart, Laurent; Fedotov, Alexandre; Feltesse, Joel; Ferencei, Jozef; Fleischer, Manfred; Fomenko, Alexander; Gabathuler, Erwin; Gayler, Joerg; Ghazaryan, Samvel; Goerlich, Lidia; Gogitidze, Nelly; Gouzevitch, Maxime; Grab, Christoph; Grebenyuk, Anastasia; Greenshaw, Timothy; Grindhammer, Guenter; Haidt, Dieter; Henderson, Rob~CW; Hladky, Jan; Hoffmann, Dirk; Horisberger, Roland; Hreus, Tomas; Huber, Florian; Jacquet, Marie; Janssen, Xavier; Jung, Hannes; Kapichine, Mikhail; Katzy, Judith; Kiesling, Christian; Klein, Max; Kleinwort, Claus; Kogler, Roman; Kostka, Peter; Kretzschmar, Jan; Krücker, Dirk; Krüger, K.; Landon, Murrough; Lange, Wolfgang; Laycock, Paul; Lebedev, Andrei; Levonian, Sergey; Lipka, Katerina; List, Benno; List, Jenny; Lobodzinski, Bogdan; Malinovski, Evgenij; Martyn, Hans-Ulrich; Maxfield, Steve~J; Mehta, Andrew; Meyer, Andreas; Meyer, Hinrich; Meyer, Joachim; Mikocki, Stanislav; Morozov, Anatoly; Müller, Katharina; Naumann, Thomas; Newman, Paul~R; Niebuhr, Carsten; Nowak, Grazyna; Olsson, Jan~Erik; Ozerov, Dmitri; Pascaud, Christian; Patel, Girish; Perez, Emmanuelle; Petrukhin, Alexey; Picuric, Ivana; Pirumov, Hayk; Pitzl, Daniel; Placakyte, Ringaile; Pokorny, Boris; Polifka, Richard; Radescu, Voica; Raicevic, Natasa; Ravdandorj, Togoo; Reimer, Petr; Rizvi, Eram; Robmann, Peter; Roosen, Robert; Rostovtsev, Andrei; Rotaru, Marina; Rusakov, Serguei; Salek, David; Sankey, Dave~PC; Sauter, Michel; Sauvan, Emmanuel; Schmitt, Stefan; Schoeffel, Laurent; Schöning, Andre; Sefkow, Felix; Shushkevich, Stanislav; Soloviev, Yuri; Sopicki, Pawel; South, David; Spaskov, Vladimir; Specka, Arnd; Steder, Michael; Stella, Bruno; Straumann, Ulrich; Sykora, Tomas; Thompson, Paul; Traynor, Daniel; Truöl, Peter; Tsakov, Ivan; Tseepeldorj, Baatar; Turnau, Jacek; Valkarova, Alice; Vallee, Claude; Van Mechelen, Pierre; Vazdik, Iakov; Wegener, Dietrich; Wünsch, Eberhard; Zacek, Jozef; Zhang, Zhiqing; Zlebcik, Radek; Zohrabyan, Hamlet; Zomer, Fabian
Signals of QCD instanton-induced processes are searched for in neutral current deep-inelastic scattering at the electron-proton collider HERA in the kinematic region defined by the Bjorken-scaling variable $x > 10^{-3}$, the inelasticity $0.2< y < 0.7$ and the photon virtuality $150 < Q^2 < 15000$ GeV$^2$. The search is performed using H1 data corresponding to an integrated luminosity of ~$351$ pb$^{-1}$. No evidence for the production of QCD instanton-induced events is observed. Upper limits on the cross section for instanton-induced processes between $1.5$~pb and $6$~pb, at $95\\%$~ confidence level, are obtained depending on the kinematic domain in which instantons could be produced. Compared to earlier publications, the limits are improved by an order of magnitude and for the first time are challenging theory predictions.
NNLO QCD corrections to the transverse momentum distribution of weak gauge bosons arXiv
Gehrmann-De Ridder, A.; Glover, E.W.N.; Huss, A.; Walker, D.M.
The transverse momentum spectra of weak gauge bosons and their ratios probe the underlying dynamics and are crucial in testing our understanding of the Standard Model. They are an essential ingredient in precision measurements, such as the $\\mathrm{W}$-boson mass extraction. To fully exploit the potential of the LHC data, we compute the second-order (NNLO) QCD corrections to the inclusive-$p_\\mathrm{T}^\\mathrm{W}$ spectrum as well as to the ratios of spectra for $\\mathrm{W}^-/\\mathrm{W}^+$ and $\\mathrm{Z}/\\mathrm{W}$. We find that the inclusion of NNLO QCD corrections considerably improves the theoretical description of the experimental CMS data and results in a substantial reduction of the residual scale uncertainties.
KMI Lattice Project on 8-Flavor QCD -- Exploration of the Walking Technicolor
Aoki, Yasumichi; Aoyama, Tatsumi; Kurachi, Masafumi; Maskawa, Toshihide; Nagai, Kei-Ichi; Ohki, Hiroshi; Shibata, Akihiro; Yamawaki, Koichi; Yamazaki, Takeshi
We present the report of the LatKMI collaboration on the lattice QCD simulation performed at the KMI computer, "φ", for the cases of 8 flavors, which is expected to be a candidate for the walking technicolor having an approximate scale invariance near the infrared fixed point. The simulation was carried out based on the highly improved staggered quark (HISQ) action. In this proceedings, we report preliminary results on the spectrum, analyzed through the chiral perturbation theory and the finite-size hyperscaling. We observe qualitatively different behavior of the 8-flavor case in contrast to the 4-flavor case which shows clear indication of the hadronic phase as in the usual QCD.
Next-to-leading order QCD corrections to paired Bc production in e+e− annihilation
Directory of Open Access Journals (Sweden)
A.V. Berezhnoy
Full Text Available We present theoretical analysis of paired Bc mesons production in e+e− annihilation at different energy scales taking into account full next-to-leading order QCD corrections. Both possible electroweak channels are considered: production via virtual photon and via virtual Z-boson. We study in detail the role of radiative QCD corrections, which were found to be significant especially at low energies. It is shown that the contribution from Z-boson is significant at high energies (s>MZ/2 especially in the case of paired production of pseudo-scalar and vector (Bc+Bc⁎ mesons. Azimuthal asymmetry induced by a P-violating weak interaction with Z-boson is also analyzed.
Bjorken sum rule in QCD with analytic coupling
Ayala, C.; Cvetič, G.; Kotikov, A. V.; Shaikhatdenov, B. G.
We present details of study of the Bjorken polarized sum rule carried out recently in [1] within the range of energies where the data were collected by JLAB collaboration, 0.05 GeV2 Theory (APT), Two-delta analytic QCD (2δanQCD), and Three-delta lattice-motivated analytic QCD in the three-loop and four-loop MiniMOM schemes (3l3δanQCD, 4l3δanQCD). The new frameworks (2δ and 3δ) with respective couplings give results which agree well with the experimental data for 0.5 GeV2 < Q 2 < 3 GeV2 already when only one higher-twist term is taken into account.
Getting more flavour out of one-flavour QCD
Melia, Tom
We argue that no notion of flavour is necessary when performing amplitude calculations in perturbative QCD with massless quarks. We show this explicitly at tree-level, using a flavour recursion relation to obtain multi-flavoured QCD from one-flavour QCD. The method relies on performing a colour decomposition, under which the one-flavour primitive amplitudes have a structure which is restricted by planarity and cyclic ordering. An understanding of SU(3)_c group theory relations between QCD primitive amplitudes and their organisation around the concept of a Dyck tree is also necessary. The one-flavour primitive amplitudes are effectively N=1 supersymmetric, and a simple consequence is that all of tree-level massless QCD can be obtained from Drummond and Henn's closed form solution to tree-level N=4 super Yang-Mills theory.
Energy Technology Data Exchange (ETDEWEB)
Jian-Ping Chen
Transverse Spin and Transverse Momemtum Dependent (TMD) distribution study has been one of the main focuses of hadron physics in recent years. The initial exploratory Semi-Incluisve Deep-Inelastic-Scattering (SIDIS) experiments with transversely polarized proton and deuteron from HERMES and COMPASS attracted great attention and lead to very active efforts in both experiments and theory. QCD factorization has been carefully studied. A SIDIS experiment on the neutron with a polarized 3He target was performed at JLab. Recently published results will be shown. Precision TMD experiments are planned at JLab after the 12 GeV energy upgrade. The approved experiments with a new SoLID spectrometer on both the proton and neutron will be presented. Proper QCD evolution treatments beyond collinear cases become crucial for the precision study of the TMDs. Experimentally, Q2 evolution and higher-twist effects are often closely related. The experience of study higher-twist effects in the cases of moments of the spin structure functions will be discussed.
QCD Evolution and Tmd/spin Experiments
Chen, Jian-Ping
Transverse Spin and Transverse Momemtum Dependent (TMD) distribution study has been one of the main focuses of hadron physics in recent years. The initial exploratory Semi-Incluisve Deep-Inelastic-Scattering (SIDIS) experiments with transversely polarized proton and deuteron from HERMES and COMPASS attracted great attention and lead to very active efforts in both experiments and theory. QCD factorization has been carefully studied. A SIDIS experiment on the neutron with a polarized 3He target was performed at JLab. Recently published results will be shown. Precision TMD experiments are planned at JLab after the 12 GeV energy upgrade. The approved experiments with a new SoLID spectrometer on both the proton and neutron will be presented. Proper QCD evolution treatments beyond collinear cases become crucial for the precision study of the TMDs. Experimentally, Q2 evolution and higher-twist effects are often closely related. The experience of study higher-twist effects in the cases of moments of the spin structure functions will be discussed.
Constituent quark masses from modified perturbative QCD
Energy Technology Data Exchange (ETDEWEB)
Cabo Montes de Oca, A. [Instituto de Cibernetica, Matematica y Fisica, La Habana (Cuba); International Institute for Theoretical and Applied Physics (IITAP), UNESCO and Iowa State University, Ames, IA (United States); Rigol Madrazo, M. [Centro de Estudios Aplicados al Desarrollo Nuclear, La Habana (Cuba)
A recently proposed modified perturbative expansion for QCD incorporating gluon condensation is employed to evaluate the quark and gluon self-energy corrections in first approximation. The results predict mass values of 1/3 of the nucleon mass for the light quarks u, d, and s and a monotonously growing variation with the current mass. The only phenomenological input is that left angle G{sup 2} right angle is evaluated up to order g{sup 2} as a function of the unique parameter C defining the modified propagator, and then C is fixed to give a current estimate of left angle g{sup 2}G{sup 2} right angle. The light quarks u and d as a result are found to be confined and the s, c, b and t ones show damped propagation modes, suggesting a model for the large differences in stability between the nucleons and the higher resonances. The above properties of quark modes diverge from the fully confinement result following from the similar gluon propagator previously considered by Munczek and Nemirovski. On the other hand, the condensate effects on the gluon self-energy furnish a tachyonic mass shell as predicted by the Fukuda analysis of gluon condensation in QCD. (orig.)
Radiative Transitions in Charmonium from Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Jozef Dudek; Robert Edwards; David Richards
Radiative transitions between charmonium states offer an insight into the internal structure of heavy-quark bound states within QCD. We compute, for the first time within lattice QCD, the transition form-factors of various multipolarities between the lightest few charmonium states. In addition, we compute the experimentally unobservable, but physically interesting vector form-factors of the {eta}{sub c}, J/{psi} and {chi}{sub c0}. To this end we apply an ambitious combination of lattice techniques, computing three-point functions with heavy domain wall fermions on an anisotropic lattice within the quenched approximation. With an anisotropy {xi} = 3 at a{sub s} {approx} 0.1 fm we find a reasonable gross spectrum and a hyperfine splitting {approx}90 MeV, which compares favorably with other improved actions. In general, after extrapolation of lattice data at non-zero Q{sup 2} to the photopoint, our results agree within errors with all well measured experimental values. Furthermore, results are compared with the expectations of simple quark models where we find that many features are in agreement; beyond this we propose the possibility of constraining such models using our extracted values of physically unobservable quantities such as the J/{psi} quadrupole moment. We conclude that our methods are successful and propose to apply them to the problem of radiative transitions involving hybrid mesons, with the eventual goal of predicting hybrid meson photoproduction rates at the GlueX experiment.
The Addendum 1 to Volume 2 of the CMS Physics TDR has been published The Heavy-Ion analysis group completed the writing of a TDR summarizing the CMS plans in using heavy ion collisions to study high density QCD. The document was submitted to the LHCC in March and presented in the Open Session of the LHCC on May 9th. The study of heavy-ion physics at the LHC is promising to be very exciting. LHC will open a new energy frontier in ultra-relativistic heavy-ion physics. The collision energy of heavy nuclei at sNN = 5.5 TeV will be thirty times larger than what is presently available at RHIC. We will certainly probe quark and gluon matter at unprecedented values of energy density. The prime goal of this research programme is to study the fundamental theory of the strong interaction - Quantum Chromodynamics (QCD) - in extreme conditions of temperature, density and parton momentum fraction (low-x). Such studies, with impressive experimental and theoretical advances in recent years thanks to the wealth of high-qua...
Lattice QCD spectroscopy for hadronic CP violation
de Vries, Jordy; Mereghetti, Emanuele; Seng, Chien-Yeah; Walker-Loud, André
The interpretation of nuclear electric dipole moment (EDM) experiments is clouded by large theoretical uncertainties associated with nonperturbative matrix elements. In various beyond-the-Standard Model scenarios nuclear and diamagnetic atomic EDMs are expected to be dominated by CP-violating pion-nucleon interactions that arise from quark chromo-electric dipole moments. The corresponding CP-violating pion-nucleon coupling strengths are, however, poorly known. In this work we propose a strategy to calculate these couplings by using spectroscopic lattice QCD techniques. Instead of directly calculating the pion-nucleon coupling constants, a challenging task, we use chiral symmetry relations that link the pion-nucleon couplings to nucleon sigma terms and mass splittings that are significantly easier to calculate. In this work, we show that these relations are reliable up to next-to-next-to-leading order in the chiral expansion in both SU (2) and SU (3) chiral perturbation theory. We conclude with a brief discussion about practical details regarding the required lattice QCD calculations and the phenomenological impact of an improved understanding of CP-violating matrix elements.
Lattice-motivated holomorphic nearly perturbative QCD
Ayala, César; Cvetič, Gorazd; Kögerler, Reinhart
Newer lattice results indicate that, in the Landau gauge at low spacelike momenta, the gluon propagator and the ghost dressing function are finite nonzero. This leads to a definition of the QCD running coupling, in a specific scheme, that goes to zero at low spacelike momenta. We construct a running coupling which fulfills these conditions, and at the same time reproduces to a high precision the perturbative behavior at high momenta. The coupling is constructed in such a way that it reflects qualitatively correctly the holomorphic (analytic) behavior of spacelike observables in the complex plane of the squared momenta, as dictated by the general principles of quantum field theories. Further, we require the coupling to reproduce correctly the nonstrange semihadronic decay rate of tau lepton which is the best measured low-momentum QCD observable with small higher-twist effects. Subsequent application of the Borel sum rules to the V + A spectral functions of tau lepton decays, as measured by OPAL Collaboration, determines the values of the gluon condensate and of the V + A six-dimensional condensate, and reproduces the data to a significantly higher precision than the usual \\overline{{MS}} running coupling.
Perturbative QCD contributions to inclusive processes
Energy Technology Data Exchange (ETDEWEB)
Ritbergen, T. van
This thesis treats the calculation of quantum corrections to a number of high energy processes that are measured in current and future accelerator experiments. The main objective of these experiments is to accurately verify the generally accepted theory of electro-weak and strong interactions, known as the Standard model, and to look for possible deviations. Most of the processes that are treated in this thesis are of a type for which the final state of of a highly energetic scattering or decay process is measured inclusively. The higher order quantum corrections discussed in this thesis are due to strong interactions. To the inclusive decay rate of Z{sup 0} bosons into all possible final states consisting of hadrons third order QCD contributions have been obtained. Also in the third order QCD an expansion for the inclusive hadronic decay rate of a {tau}-lepton was obtained. Then the top-quark-mass effects on the decay channels of a Higgs boson: Higgs{yields}b-quarks and Higgs{yields}gluons, were investigated. Thereafter the calculation of 3-loop contributions to the deep-inelastic lepton-nucleon scattering process is discussed. Finally the 3-loop contributions to the q{sup 2}-dependence of the lower moments {integral}{sub 0}{sup 1}x{sup N-1}F(x,q{sup 2})dx, N=2,4,6,8 of the structure functions F{sub 2} and F{sub L} were obtained. (orig./HSI).
Composite inflation from super Yang-Mills theory, orientifold, and one-flavor QCD
DEFF Research Database (Denmark)
Channuie, P.; Jorgensen, J. J.; Sannino, F.
Recent investigations have shown that inflation can be driven by four-dimensional strongly interacting theories nonminimally coupled to gravity. We explore this paradigm further by considering composite inflation driven by orientifold field theories. The advantage of using these theories resides ...... nonminimally coupled QCD theory of inflation. The scale of composite inflation, for all the models presented here, is of the order of 10(16) GeV. Unitarity studies of the inflaton scattering suggest that the cutoff of the model is at the Planck scale. DOI: 10.1103/PhysRevD.86.125035...
Net baryons in heavy-ion collisions and the QCD critical point
Antoniou, Nikos G
The net-baryon density at midrapidity is proposed as an order parameter in the search for the QCD critical point in heavy ion collisions. As a function of the initial energy and the total number of participants, this quantity obeys a scaling law, dictated by the critical exponents of the appropriate universality class. The corresponding scaling variable specifies the proximity of a given experiment to the critical point. Within this framework, measurements at the SPS are discussed and predictions for RHIC and LHC are extracted. (12 refs).
QCD-improved limits from neutrinoless double beta decay
Arbeláez, C.; González, M.; Kovalenko, S. G.; Hirsch, M.
We analyze the impact of QCD corrections on limits derived from neutrinoless double beta decay (0 ν β β ). As demonstrated previously, the effect of the color mismatch arising from loops with gluons linking the quarks from different color-singlet currents participating in the effective operators has a dramatic impact on the predictions for some particular Wilson coefficients. Here, we consider all possible contributions from heavy particle exchange, i.e. the so-called short-range mechanism of 0 ν β β decay. All high-scale models (HSM) in this class match at some scale around a ˜ few TeV with the corresponding effective theory, containing a certain set of effective dimension-9 operators. Many of these HSM receive contributions from more than one of the basic operators and we calculate limits on these models using the latest experimental data. We also show with one nontrivial example, how to derive limits on more complicated models, in which many different Feynman diagrams contribute to 0 ν β β decay, using our general method.
Nonperturbative QCD and elastic processes at CEBAF energies
Energy Technology Data Exchange (ETDEWEB)
Radyushkin, A.V. [Old Dominion Univ., Norfolk, VA (United States)]|[Continuous Electron Beam Accelerator Facility, Newport News, VA (United States)
The author outlines how one can approach nonperturbative aspects of the QCD dynamics studying elastic processes at energies accessible at upgraded CEBAF. The author`s point is that, in the absence of a complete theory of the nonperturbative effects, a possible way out is based on a systematic use of the QCD factorization procedure which separates theoretically understood ({open_quotes}known{close_quotes}) short-distance effects and nonperturbative ({open_quotes}unknown{close_quotes}) long-distance ones. The latter include hadronic distribution amplitudes, soft components of hadronic form factors etc. Incorporating the QCD sum rule version of the QCD factorization approach, one can relate these nonperturbative functions to more fundamental objects, vacuum condensates, which accumulate information about the nonperturbative structure of the QCD vacuum. The emerging QCD sum rule picture of hadronic form factors is characterized by a dominant role of essentially nonperturbative effects in the few GeV region, with perturbative mechanisms starting to show up for momentum transfers Q{sup 2} closer to 10 GeV{sup 2} and higher. Thus, increasing CEBAF energy provides a unique opportunity for a precision study of interplay between the perturbative and nonperturbative phenomena in the QCD description of elastic processes.
Perturbative corrections to Λ{sub b}→Λ form factors from QCD light-cone sum rules
Energy Technology Data Exchange (ETDEWEB)
Wang, Yu-Ming [Fakultät für Physik, Universität Wien,Boltzmanngasse 5, 1090 Vienna (Austria); Physik Department T31, Technische Universität München,James-Franck-Straße 1, D-85748 Garching (Germany); Shen, Yue-Long [College of Information Science and Engineering, Ocean University of China,Songling Road 238, Qingdao, Shandong 266100 (China)
We compute radiative corrections to Λ{sub b}→Λ from factors, at next-to-leading logarithmic accuracy, from QCD light-cone sum rules with Λ{sub b}-baryon distribution amplitudes. Employing the diagrammatic approach factorization of the vacuum-to-Λ{sub b}-baryon correlation function is justified at leading power in Λ/m{sub b}, with the aid of the method of regions. Hard functions entering the factorization formulae are identical to the corresponding matching coefficients of heavy-to-light currents from QCD onto soft-collinear effective theory. The universal jet function from integrating out the hard-collinear fluctuations exhibits richer structures compared with the one involved in the factorization expressions of the vacuum-to-B-meson correlation function. Based upon the QCD resummation improved sum rules we observe that the perturbative corrections at O(α{sub s}) shift the Λ{sub b}→Λ from factors at large recoil significantly and the dominant contribution originates from the next-to-leading order jet function instead of the hard coefficient functions. Having at hand the sum rule predictions for the Λ{sub b}→Λ from factors we further investigate several decay observables in the electro-weak penguin Λ{sub b}→Λ ℓ{sup +}ℓ{sup −} transitions in the factorization limit (i.e., ignoring the "non-factorizable' hadronic effects which cannot be expressed in terms of the Λ{sub b}→Λ from factors), including the invariant mass distribution of the lepton pair, the forward-backward asymmetry in the dilepton system and the longitudinal polarization fraction of the leptonic sector.
QCD effective action with dressing functions: Consistency checks in the perturbative regime
Cvetič, Gorazd; Kondrashuk, Igor; Schmidt, Iván
In a previous paper, we presented a solution to the Slavnov-Taylor identity for the QCD effective action, and argued that the action terms containing (anti)ghost fields are unique. These terms have the same form as those in the classical action, but the gluon and (anti)ghost effective fields are convoluted with gluon and ghost dressing functions GA and Gc, the latter containing perturbative and nonperturbative effects (but not including the solitonlike vacuum effects). In the present work we show how perturbative QCD (PQCD) can be incorporated into the framework of this action, and we present explicit one-loop PQCD expressions for GA and Gc. We then go on to check the consistency of the results obtained by considering an antighost Dyson-Schwinger equation (DSE). By solving the relations that result from the Legendre transformation leading to the effective action, we obtain the effective fields as power expansions of sources. We check explicitly that the aforementioned one-loop functions GA and Gc satisfy the antighost DSE at the linear source level. We further explicitly check that these one-loop GA and Gc have a regularization scale and momentum dependence consistent with the antighost DSE at the quadratic source level. These checks suggest that the effective action with dressing functions represents a consistent framework for treating QCD, at least at the one-loop level.
Differential distributions for t-channel single top-quark production and decay at next-to-next-to-leading order in QCD
Energy Technology Data Exchange (ETDEWEB)
Berger, Edmond L.; Gao, Jun; Zhu, Hua Xing
We present a detailed phenomenological study of the next-to-next-to-leading order (NNLO) QCD corrections for t-channel single top (anti-)quark production and its semi-leptonic decay at the CERN Large Hadron Collider (LHC). We find the NNLO corrections for the total inclusive rates at the LHC with different center of mass energies are generally smaller than the NLO corrections, indicative of improved convergence. However, they can be large for differential distributions, reaching a level of 10% or more in certain regions of the transverse momentum distributions of the top (anti-)quark and the pseudo-rapidity distributions of the leading jet in the event. In all cases the perturbative hard-scale uncertainties are greatly reduced after the NNLO corrections are included. We also show a comparison of the normalized parton-level distributions to recent data from the 8 TeV measurement of the ATLAS collaboration. The NNLO corrections tend to shift the theoretical predictions closer to the measured transverse momentum distribution of the top (anti)-quark. Importantly, for the LHC at 13 TeV, we present NNLO cross sections in a fiducial volume with decays of the top quark included.
Precision Light Flavor Physics from Lattice QCD
Murphy, David
In this thesis we present three distinct contributions to the study of light flavor physics using the techniques of lattice QCD. These results are arranged into four self-contained papers. The first two papers concern global fits of the quark mass, lattice spacing, and finite volume dependence of the pseudoscalar meson masses and decay constants, computed in a series of lattice QCD simulations, to partially quenched SU(2) and SU(3) chiral perturbation theory (chiPT). These fits determine a subset of the low energy constants of chiral perturbation theory -- in some cases with increased precision, and in other cases for the first time -- which, once determined, can be used to compute other observables and amplitudes in chiPT. We also use our formalism to self-consistently probe the behavior of the (asymptotic) chiral expansion as a function of the quark masses by repeating the fits with different subsets of the data. The third paper concerns the first lattice QCD calculation of the semileptonic K0 → pi-l +nul ( Kl3) form factor at vanishing momentum transfer, f+Kpi(0), with physical mass domain wall quarks. The value of this form factor can be combined with a Standard Model analysis of the experimentally measured K0 → pi -l+nu l decay rate to extract a precise value of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element Vus, and to test unitarity of the CKM matrix. We also discuss lattice calculations of the pion and kaon decay constants, which can be used to extract Vud through an analogous Standard Model analysis of experimental constraints on leptonic pion and kaon decays. The final paper explores the recently proposed exact one flavor algorithm (EOFA). This algorithm has been shown to drastically reduce the memory footprint required to simulate single quark flavors on the lattice relative to the widely used rational hybrid Monte Carlo (RHMC) algorithm, while also offering modest O(20%) speed-ups. We independently derive the exact one flavor action, explore its
Large scale patterns of antimicrofouling defenses in the hard coral Pocillopora verrucosa in an environmental gradient along the Saudi Arabian coast of the Red Sea.
Directory of Open Access Journals (Sweden)
Martin Wahl
Full Text Available Large scale patterns of ecologically relevant traits may help identify drivers of their variability and conditions beneficial or adverse to the expression of these traits. Antimicrofouling defenses in scleractinian corals regulate the establishment of the associated biofilm as well as the risks of infection. The Saudi Arabian Red Sea coast features a pronounced thermal and nutritional gradient including regions and seasons with potentially stressful conditions to corals. Assessing the patterns of antimicrofouling defenses across the Red Sea may hint at the susceptibility of corals to global change. We investigated microfouling pressure as well as the relative strength of 2 alternative antimicrofouling defenses (chemical antisettlement activity, mucus release along the pronounced environmental gradient along the Saudi Arabian Red Sea coast in 2 successive years. Microfouling pressure was exceptionally low along most of the coast but sharply increased at the southernmost sites. Mucus release correlated with temperature. Chemical defense tended to anti-correlate with mucus release. As a result, the combined action of mucus release and chemical antimicrofouling defense seemed to warrant sufficient defense against microbes along the entire coast. In the future, however, we expect enhanced energetic strain on corals when warming and/or eutrophication lead to higher bacterial fouling pressure and a shift towards putatively more costly defense by mucus release.
The transverse structure of the pion in momentum space inspired by the AdS/QCD correspondence
Bacchetta, Alessandro; Cotogno, Sabrina; Pasquini, Barbara
We study the internal structure of the pion using a model inspired by the AdS/QCD correspondence. The holographic approach provides the light-front wave function (LFWF) for the leading Fock-state component of the pion. We adopt two different forms for the LFWF derived from the AdS/QCD soft-wall model, with free parameters fitted to the available experimental information on the pion electromagnetic form factor and the leading-twist parton distribution function. The intrinsic scale of the model is taken as an additional fit parameter. Within this framework, we provide predictions for the unpolarized transverse momentum dependent parton distribution (TMD), and discuss its property both at the scale of the model and after TMD evolution to higher scales that are relevant for upcoming experimental measurements.
Wilson Dslash Kernel From Lattice QCD Optimization
Energy Technology Data Exchange (ETDEWEB)
Joo, Balint [Jefferson Lab, Newport News, VA; Smelyanskiy, Mikhail [Parallel Computing Lab, Intel Corporation, California, USA; Kalamkar, Dhiraj D. [Parallel Computing Lab, Intel Corporation, India; Vaidyanathan, Karthikeyan [Parallel Computing Lab, Intel Corporation, India
Lattice Quantum Chromodynamics (LQCD) is a numerical technique used for calculations in Theoretical Nuclear and High Energy Physics. LQCD is traditionally one of the first applications ported to many new high performance computing architectures and indeed LQCD practitioners have been known to design and build custom LQCD computers. Lattice QCD kernels are frequently used as benchmarks (e.g. 168.wupwise in the SPEC suite) and are generally well understood, and as such are ideal to illustrate several optimization techniques. In this chapter we will detail our work in optimizing the Wilson-Dslash kernels for Intel Xeon Phi, however, as we will show the technique gives excellent performance on regular Xeon Architecture as well.
The lightest hybrid meson supermultiplet in QCD
Energy Technology Data Exchange (ETDEWEB)
Dudek, Jozef J
We interpret the spectrum of meson states recently obtained in non-perturbative lattice QCD calculations in terms of constituent quark-antiquark bound states and states, called 'hybrids', in which the q{bar q} pair is supplemented by an excitation of the gluonic field. We identify a lightest supermultiplet of hybrid mesons with J{sup PC} = (0,1,2){sup {-+}}, 1{sup -} built from a gluonic excitation of chromomagnetic character coupled to q{bar q} in an S-wave. The next lightest hybrids are suggested to be quark orbital excitations with the same gluonic excitation, while the next distinct gluonic excitation is significantly heavier. Existing models of gluonic excitations are compared to these findings and possible phenomenological consequences explored.
Directory of Open Access Journals (Sweden)
Rizvi Eram
Full Text Available The HERA ep collider experiments have measured the proton structure functions over a wide kinematic range. New data from the H1 experiment now extend the range to higher 4-momentum transfer (√Q2 over which a precision of ~ 2% is achieved in the neutral current channel. A factor of two reduction in the systematic uncertainties over previous measurement is attained. The charged current structure function measurements are also significantly improved in precision. These data, when used in QCD analyses of the parton density functions (PDFs reduce the PDF uncertainties particularly at high momentum fractions x which is relevant to predictions for the LHC experiments as well as low energy neutrino scattering cross sections.
Neutrinoless double beta decay from lattice QCD
Nicholson, Amy; Cheng, Chia; Berkowitz, Evan; Rinaldi, Enrico; Walker-Loud, Andre; Vranas, Pavlos; Kurth, Thorsten; Clark, M. A.; Garron, Nicolas; Tiburzi, Brian; Monge-Camacho, Henry; Brantley, David; Joo, Balint; Callat Collaboration
Lepton number-violating neutrinoless double beta decay is a natural consequence of Majorana neutrinos and many BSM theories, and, if observed, could potentially explain the observed matter/anti-matter asymmetry in the universe. Several experimental searches for these processes using nuclear sources are planned and/or underway worldwide, and understanding quantitatively how neutrinoless double beta decay would manifest in nuclear environments is key for interpreting any observed signals. While long-range, light neutrino exchange is the most common mechanism studied, short-range interactions involving heavy mediator exchange may also contribute. In this talk I will give an overview of the microscopic observables relevant for experimental searches for neutrinoless double beta decay which may be calculated directly from QCD using lattice methods, and present results for short-range matrix elements contributing to pion exchange diagrams between nucleons.
Spectroscopy of charmed baryons from lattice QCD
Padmanath, M; Mathur, Nilmani; Peardon, Michael
We present the ground and excited state spectra of singly, doubly and triply charmed baryons by using dynamical lattice QCD. A large set of baryonic operators that respect the symmetries of the lattice and are obtained after subduction from their continuum analogues are utilized. Using novel computational techniques correlation functions of these operators are generated and the variational method is exploited to extract excited states. The lattice spectra that we obtain have baryonic states with well-defined total spins up to 7/2 and the low lying states remarkably resemble the expectations of quantum numbers from SU(6) $\\otimes$ O(3) symmetry. Various energy splittings between the extracted states, including splittings due to hyperfine as well as spin-orbit coupling, are considered and those are also compared against similar energy splittings at other quark masses.
Sonification of Monopoles and Chaos in QCD
de Campo, Alberto; Hörmann, Natascha; Markum, Harald; Plessas, Willibald; Vogt, Katharina
Sonification is defined as the use of non-speech audio to extract information from data and it represents the sound analogue to graphical visualization. The method is applied in several disciplines from economy to medicine to physics. Sonification might also help in analyzing data of lattice QCD. It could assist, together with graphical display, to examine the behavior of lattice observables as a function of parameters like gauge coupling, quark mass, etc. Sonification might further be used to identify unique characteristics of single gauge-field configurations out of many such as, for example, the topological content. In order to demonstrate the methodology for quantum chromodynamics we analyze the monopole order parameter from the confinement to the deconfinement phase. We further produce a sound file for the Lyapunov exponents of classical U(1) and SU(2) gauge theory. The studies are also part of the development of program packages for audio browsing within the interdisciplinary research project SonEnvir ().
Asymmetric dense matter in holographic QCD
Directory of Open Access Journals (Sweden)
Shin Ik Jae
Full Text Available We study asymmetric dense matter in holographic QCD.We construct asymmetric dense matter by considering two quark flavor branes with dierent quark masses in a D4/D6/D6 model. To calculate the symmetry energy in nuclear matter, we consider two quarks with equal masses and observe that the symmetry energy increases with the total charge showing the stiff dependence. This behavior is universal in the sense that the result is independent of parameters in the model. We also study strange (or hyperon matter with one light and one intermediate mass quarks. In addition to the vacuum properties of asymmetric matter, we calculate meson masses in asymmetric dense matter and discuss our results in the light of in-medium kaon masses.
Spectroscopy of charmed baryons from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Padmanath, M. [Univ. of Graz (Austria). Inst. of Physics; Edwards, Robert G. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Mathur, Nilmani [Tata Institute of Fundamental Research, Bombay (India); Peardon, Michael [Trinity College, Dublin (Ireland)
We present the ground and excited state spectra of singly, doubly and triply charmed baryons by using dynamical lattice QCD. A large set of baryonic operators that respect the symmetries of the lattice and are obtained after subduction from their continuum analogues are utilized. Using novel computational techniques correlation functions of these operators are generated and the variational method is exploited to extract excited states. The lattice spectra that we obtain have baryonic states with well-defined total spins up to 7/2 and the low lying states remarkably resemble the expectations of quantum numbers from SU(6) x O(3) symmetry. Various energy splittings between the extracted states, including splittings due to hyperfine as well as spin-orbit coupling, are considered and those are also compared against similar energy splittings at other quark masses.
HERAFitter, Open Source QCD Fit Project
Alekhin, S.; Belov, P.; Borroni, S.; Botje, M.; Britzger, D.; Camarda, S.; Cooper-Sarkar, A.M.; Daum, K.; Diaconu, C.; Feltesse, J.; Gizhko, A.; Glazov, A.; Guffanti, A.; Guzzi, M.; Hautmann, F.; Jung, A.; Jung, H.; Kolesnikov, V.; Kowalski, H.; Kuprash, O.; Kusina, A.; Levonian, S.; Lipka, K.; Lobodzinski, B.; Lohwasser, K.; Luszczak, A.; Malaescu, B.; McNulty, R.; Myronenko, V.; Naumann-Emme, S.; Nowak, K.; Olness, F.; Perez, E.; Pirumov, H.; Plačakytė, R.; Rabbertz, K.; Radescu, V.; Sadykov, R.; Salam, G.P.; Sapronov, A.; Schöning, A.; Schörner-Sadenius, T.; Shushkevich, S.; Slominski, W.; Spiesberger, H.; Starovoitov, P.; Sutton, M.; Tomaszewska, J.; Turkot, O.; Vargas, A.; Watt, G.; Wichmann, K.
HERAFitter is an open-source package that provides a framework for the determination of the parton distribution functions (PDFs) of the proton and for many different kinds of analyses in Quantum Chromodynamics (QCD). It encodes results from a wide range of experimental measurements in lepton-proton deep inelastic scattering and proton-proton (proton-antiproton) collisions at hadron colliders. These are complemented with a variety of theoretical options for calculating PDF-dependent cross section predictions corresponding to the measurements. The framework covers a large number of the existing methods and schemes used for PDF determination. The data and theoretical predictions are brought together through numerous methodological options for carrying out PDF fits and plotting tools to help visualise the results. While primarily based on the approach of collinear factorisation, HERAFitter also provides facilities for fits of dipole models and transverse-momentum dependent PDFs. The package can be used to study t...
Role of QCD monopoles in jet quenching
Ramamurti, Adith; Shuryak, Edward
QCD monopoles are magnetically charged quasiparticles whose Bose-Einstein condensation (BEC) at T T >Tc is responsible for the unusual kinetic properties of quark-gluon plasma. In this paper, we study the contribution of the monopoles to jet quenching phenomenon, using the Baier-Dokshitzer-Mueller-Peigne-Schiff framework and hydrodynamic backgrounds. In the lowest order for cross sections, we calculate the nuclear modification factor, RAA, and azimuthal anisotropy, v2, of jets, as well as the dijet asymmetry, Aj, and compare those to the available data. We find relatively good agreement with experiment when using realistic hydrodynamic backgrounds. In addition, we find that event-by-event fluctuations are not necessary to reproduce RAA and v2 data, but play a role in Aj. Since the monopole-induced effects are maximal at T ≈Tc, we predict that their role should be significantly larger, relative to quarks and gluons, at lower RHIC energies.
QCD Sum Rules Study of X(4350)
Mo, Zeng; Cui, Chun-Yu; Liu, Yong-Lu; Huang, Ming-Qiu
The QCD sum rule approach is used to analyze the nature of the recently observed new resonance X(4350), which is assumed to be a diquark-antidiquark state [cs][bar cbar s] with JPC = 1-+. The interpolating current representing this state is proposed. In the calculation, contributions of operators up to dimension six are included in the operator product expansion (OPE), as well as terms which are linear in the strange quark mass ms. We find m1-+ = (4.82 ± 0.19) GeV, which is not compatible with the X(4350) structure as a 1-+ tetraquark state. Finally, we also discuss the difference of a four-quark state's mass whether the state's interpolating current has a definite charge conjugation.
Hauser, D. L.; Buras, D. F.; Corbin, J. M.
Rubber-hardness tester modified for use on rigid polyurethane foam. Provides objective basis for evaluation of improvements in foam manufacturing and inspection. Typical acceptance criterion requires minimum hardness reading of 80 on modified tester. With adequate correlation tests, modified tester used to measure indirectly tensile and compressive strengths of foam.
Non-Markovian Monte Carlo Algorithm for the Constrained Markovian Evolution in QCD
Jadach, Stanislaw
We revisit the challenging problem of finding an efficient Monte Carlo (MC) algorithm solving the constrained evolution equations for the initial-state QCD radiation. The type of the parton (quark, gluon) and the energy fraction x of the parton exiting emission chain (entering hard process) are predefined, i.e. constrained throughout the evolution. Such a constraint is mandatory for any realistic MC for the initial state QCD parton shower. We add one important condition: the MC algorithm must not require the a priori knowledge of the full numerical exact solutions of the evolution equations, as is the case in the popular ``Markovian MC for backward evolution''. Our aim is to find at least one solution of this problem that would function in practice. Finding such a solution seems to be definitely within the reach of the currently available computer CPUs and the sophistication of the modern MC techniques. We describe in this work the first example of an efficient solution of this kind. Its numerical implementat...
Improved estimates of the B{sub (s)}→VV decays in perturbative QCD approach
Energy Technology Data Exchange (ETDEWEB)
Zou, Zhi-Tian; Li, Ying [Yantai Univ. (China). Dept. of Physics; Ali, Ahmed [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Lue, Cai-Dian [Institute of High Energy Physics, Beijing, BJ (China); Theoretical Physics Center for Science Facilities, CAS, Beijing (China); Liu, Xin [Jiangsu Normal Univ., Xuzhou (China). School of Physics and Electronic Engineering
We reexamine the branching ratios, CP-asymmetries, and other observables in a large number of B{sub q}→VV(q=u,d,s) decays in the perturbative QCD (PQCD) approach, where V denotes a light vector meson (ρ,K{sup *},ω,φ). The essential difference between this work and the earlier similar works is of parametric origin and in the estimates of the power corrections related to the ratio r{sup 2}{sub i}=m{sup 2}{sub V{sub i}}/m{sup 2}{sub B} (i=2,3) (m{sub V} and m{sub B} denote the masses of the vector and B meson, respectively). In particular, we use up-to-date distribution amplitudes for the final state mesons and keep the terms proportional to the ratio r{sup 2}{sub i} in our calculations. Our updated calculations are in agreement with the experimental data, except for a limited number of decays which we discuss. We emphasize that the penguin annihilation and the hard-scattering emission contributions are essential to understand the polarization anomaly, such as in the B→φK{sup *} and B{sub s}→φφ decay modes. We also compare our results with those obtained in the QCD factorization (QCDF) approach and comment on the similarities and differences, which can be used to discriminate between these approaches in future experiments.
Comprehensive Hard Materials deals with the production, uses and properties of the carbides, nitrides and borides of these metals and those of titanium, as well as tools of ceramics, the superhard boron nitrides and diamond and related compounds. Articles include the technologies of powder production (including their precursor materials), milling, granulation, cold and hot compaction, sintering, hot isostatic pressing, hot-pressing, injection moulding, as well as on the coating technologies for refractory metals, hard metals and hard materials. The characterization, testing, quality assurance and applications are also covered. Comprehensive Hard Materials provides meaningful insights on materials at the leading edge of technology. It aids continued research and development of these materials and as such it is a critical information resource to academics and industry professionals facing the technological challenges of the future. Hard materials operate at the leading edge of technology, and continued res...
W production at LHC: lepton angular distributions and reference frames for probing hard QCD
Energy Technology Data Exchange (ETDEWEB)
Richter-Was, E. [Jagiellonian University, Institute of Physics, Krakow (Poland); Was, Z. [Institute of Nuclear Physics Polish Academy of Sciences, Krakow (Poland)
Precision tests of the Standard Model in the Strong and Electroweak sectors play a crucial role, among the physics program of LHC experiments. Because of the nature of proton-proton processes, observables based on the measurement of the direction and energy of final state leptons provide the most precise probes of such processes. In the present paper, we concentrate on the angular distribution of leptons from W → lν decays in the lepton-pair rest-frame. The vector nature of the intermediate state imposes that distributions are to a good precision described by spherical harmonics of at most second order. We argue, that contrary to general belief often expressed in the literature, the full set of angular coefficients can be measured experimentally, despite the presence of escaping detection neutrino in the final state. There is thus no principle difference with respect to the phenomenology of the Z/γ → l{sup +}l{sup -} Drell-Yan process. We show also, that with the proper choice of the reference frames, only one coefficient in this polynomial decomposition remains sizable, even in the presence of one or more high p{sub T} jets. The necessary stochastic choice of the frames relies on probabilities independent from any coupling constants. In this way, electroweak effects (dominated by the V - A nature of W couplings to fermions), can be better separated from the ones of strong interactions. The separation is convenient for the measurements interpretation. (orig.)
Soft and semi-hard QCD dynamics in p-p collisions at CMS
Van Remortel, Nick
Several new results have been released for public display over the last year. In particular there are new CMS results on identified particle spectra, and several new Underlying Event measurements. I will discuss in general lines the scope of these measurements and the interpretation of the results.
Novel QCD Aspects of Hard Diffraction,Antishadowing, and Single-Spin Asymmetries
Energy Technology Data Exchange (ETDEWEB)
Brodsky, S.
It is usually assumed--following the parton model--that the leading-twist structure functions measured in deep inelastic lepton-proton scattering are simply the probability distributions for finding quarks and gluons in the target nucleon. In fact, gluon exchange between the outgoing quarks and the target spectators effects the leading-twist structure functions in a profound way, leading to diffractive leptoproduction processes, shadowing and antishadowing of nuclear structure functions, and target spin asymmetries, physics not incorporated in the light-front wavefunctions of the target computed in isolation. In particular, final-state interactions from gluon exchange lead to single-spin asymmetries in semi-inclusive deep inelastic lepton-proton scattering which are not power-law suppressed in the Bjorken limit. The shadowing and antishadowing of nuclear structure functions in the Gribov-Glauber picture is due respectively to the destructive and constructive interference of amplitudes arising from the multiple-scattering of quarks in the nucleus. The effective quark-nucleon scattering amplitude includes Pomeron and Odderon contributions from multi-gluon exchange as well as Reggeon quark-exchange contributions. Part of the anomalous NuTeV result for sin{sup 2} {theta}{sub W} could be due to the non-universality of nuclear antishadowing for charged and neutral currents. Detailed measurements of the nuclear dependence of individual quark structure functions are thus needed to establish the distinctive phenomenology of shadowing and antishadowing and to make the NuTeV results definitive. I also discuss diffraction dissociation as a tool for resolving hadron substructure Fock state by Fock state and for producing leading heavy quark systems.
QCD-motivated description of very high energy particle interactions
Gaisser, T. K.; Halzen, F.
Cross sections for the production of secondaries with large transverse momentum can become comparable to the total cross section in the TeV energy range. It is argued that the onset of this effect is observed at sub TeV energies via an increase of the rapidity distribution near y = 0, an increase of p sub T with energy and, most directly, via a correlation between p sub T and multiplicity. If indeed scaling violations are associated with the hard scattering of partons, then scaling violations are largely confined to the central region and have little effect on cosmic ray data which are sensitive to the forward fragmentation region.
Light meson gas in the QCD vacuum and oscillating universe
Prokhorov, George; Pasechnik, Roman
We have developed a phenomenological effective quantum-field theoretical model describing the "hadron gas" of the lightest pseudoscalar mesons, scalar σ-meson and σ-vacuum, i.e. the expectation value of the σ-field, at finite temperatures. The corresponding thermodynamic approach was formulated in terms of the generating functional derived from the effective Lagrangian providing the basic thermodynamic information about the "meson plasma + QCD condensate" system. This formalism enables us to study the QCD transition from the hadron phase with direct implications for cosmological evolution. Using the hypothesis about a positively-definite QCD vacuum contribution stochastically produced in early universe, we show that the universe could undergo a series of oscillations during the QCD epoch before resuming unbounded expansion.
Novel QCD Phenomena at the LHeC
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins
The proposed electron-proton/ion collider at CERN, the LHeC, can test fundamental and novel aspects of QCD and electroweak interactions as well as explore physics beyond the standard model over an exceptionally large kinematic range.
The spin content of the proton in full QCD
Energy Technology Data Exchange (ETDEWEB)
Alles, B. [Milan Univ. (Italy). Dipt. di Fisica; Boyd, G. [Center for Computational Physics, University of Tsukuba, Tsukuba, Ibaraki 305 (Japan); D`Elia, M.; Di Giacomo, A. [Dipartimento di Fisica, Universita di Pisa and INFN, Piazza Torricelli 2, 56126 Pisa (Italy)
We present preliminary results on the proton spin structure function in full QCD. The measurement has been done using 4 flavours of staggered fermions and an improved definition of the lattice topological charge density. (orig.). 17 refs.
QCD Studies at the LHC with the ATLAS Detector
Eckweiler, S; The ATLAS collaboration
This paper describes a selection of early QCD analyses, planned to be performed with the ATLAS experiment. Measurements of underlying event properties and minimum bias events in early data are discussed. Selected analyses including jets are presented.
Academic Training: QCD: are we ready for the LHC
2006-2007 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 4, 5, 6, 7 December, from 11:00 to 12:00 4, 5, 6 December - Main Auditorium, bldg. 500, 7 December - TH Auditorium, bldg. 4 - 3-006 QCD: are we ready for the LHC S. FRIXIONE / INFN, Genoa, Italy The LHC energy regime poses a serious challenge to our capability of predicting QCD reactions to the level of accuracy necessary for a successful programme of searches for physics beyond the Standard Model. In these lectures, I'll introduce basic concepts in QCD, and present techniques based on perturbation theory, such as fixed-order and resummed computations, and Monte Carlo simulations. I'll discuss applications of these techniques to hadron-hadron processes, concentrating on recent trends in perturbative QCD aimed at improving our understanding of LHC phenomenology.
QCD Background Estimation From Data for Supersymmetry Searches at ATLAS
Owen, S; The ATLAS collaboration
A major challenge in the search for Supersymmetry (SUSY) with no leptons at ATLAS is the measurement of the background from QCD multi-jet production. A data-driven estimation is very important for this background; it is difficult to accurately estimate jet response tails using Monte Carlo (MC) simulation and furthermore it is impossible to generate sufficient MC simulated QCD events, given the high QCD cross section. The jet smearing method is a fully data-driven technique which uses a measurement of the jet response function to estimate the QCD background to SUSY through the 'smearing' of seed events. The technique has been validated using MC simulation and is now being used on ATLAS data.
Tevatron-for-LHC Report of the QCD Working Group
Energy Technology Data Exchange (ETDEWEB)
Albrow, Michael G.; Begel, M.; Bourilkov, D.; Campanelli, M.; Chlebana, F.; De Roeck, A.; Dittmann, J.R.; Ellis, S.D.; Field, B.; Field, R.; Gallinaro, M.; /Fermilab
The experiments at Run 2 of the Tevatron have each accumulated over 1 fb{sup -1} of high-transverse momentum data. Such a dataset allows for the first precision (i.e. comparisons between theory and experiment at the few percent level) tests of QCD at a hadron collider. While the Large Hadron Collider has been designed as a discovery machine, basic QCD analyses will still need to be performed to understand the working environment. The Tevatron-for-LHC workshop was conceived as a communication link to pass on the expertise of the Tevatron and to test new analysis ideas coming from the LHC community. The TeV4LHC QCD Working Group focused on important aspects of QCD at hadron colliders: jet definitions, extraction and use of Parton Distribution Functions, the underlying event, Monte Carlo tunes, and diffractive physics. This report summarizes some of the results achieved during this workshop.
Glueball and meson spectrum in large-N massless QCD
Bochicchio, Marco
We provide outstanding numerical evidence that in large-N massless QCD the joint spectrum of the masses squared, for fixed integer spin s and unspecified parity and charge conjugation, obeys exactly the following laws: m_k^2 = (k+s/2) Lambda_QCD^2 for s even, m_k^2 = 2(k+s/2) Lambda_QCD^2 for s odd, k = 1,2,... for glueballs, and m_n^2 = 1/2 (n+s/2) Lambda_QCD^2, n = 0,1,... for mesons. One of the striking features of these laws is that they imply that the glueball and meson masses squared fo...
How well does QCD work for photon-photon collisions?
Wengler, Thorsten
The performance of QCD in describing hadronic photon-photon collisions is investigated in the light of recent measurements from LEP on di-jet production, light hadron transverse momentum spectra, and heavy quark production.
Chiral phase transition of $N_f$=2+1 and 3 QCD at vanishing baryon chemical potential
Ding, Heng-Tong
We present updated results on chiral phase structure in (2+1)-flavor ($N_f$=2+1) and 3-flavor ($N_f=3$) QCD based on the simulations using Highly Improved Staggered Quarks on lattices with temporal extent $N_\\tau$ =6 at vanishing baryon chemical potential. In $N_f$=2+1 QCD we have performed simulations with a strange quark fixed to its physical value and two degenerate light quarks whose values are adjusted to have 5 values of Goldstone pion masses in the region of 160 - 80 MeV in the continuum limit. The universal scaling behavior of chiral condensates as well as chiral susceptibilities is discussed and the tri-critical point is suggested to be located below the physical point, i.e. at smaller than physical strange quark mass. In $N_f$=3 QCD simulations with 6 different masses of 3 degenerate quarks corresponding to the Goldstone pion masses in the region of 230 - 80 MeV have also been performed. Our results suggest that the QCD transition with these values of quark masses is of crossover type and an upper b...
Magnetic fields in QCD vacuum: A lattice view
Energy Technology Data Exchange (ETDEWEB)
Buividovich, P.V. [Regensburg University, Institute for Theoretical Physics, Regensburg (Germany)
We review the basic phenomena in QCD subject to strong magnetic fields which are accessible in experiment and can be also studied in lattice QCD simulations: enhanced fluctuations of electric current and electric dipole moment, the negative magnetoresistivity and the inverse magnetic catalysis. We comment on the possibility of experimental detection of negative magnetoresistivity by analysing the angular distributions of dilepton pairs in off-central heavy-ion collisions. (orig.)
Volume Independence in Large Nc QCD-like Gauge Theories
Energy Technology Data Exchange (ETDEWEB)
Kovtun, Pavel; Unsal, Mithat; Yaffe, Laurence G.
Volume independence in large N{sub c} gauge theories may be viewed as a generalized orbifold equivalence. The reduction to zero volume (or Eguchi-Kawai reduction) is a special case of this equivalence. So is temperature independence in confining phases. A natural generalization concerns volume independence in ''theory space'' of quiver gauge theories. In pure Yang-Mills theory, the failure of volume independence for sufficiently small volumes (at weak coupling) due to spontaneous breaking of center symmetry, together with its validity above a critical size, nicely illustrate the symmetry realization conditions which are both necessary and sufficient for large N{sub c} orbifold equivalence. The existence of a minimal size below which volume independence fails also applies to Yang-Mills theory with antisymmetric representation fermions [QCD(AS)]. However, in Yang-Mills theory with adjoint representation fermions [QCD(Adj)], endowed with periodic boundary conditions, volume independence remains valid down to arbitrarily small size. In sufficiently large volumes, QCD(Adj) and QCD(AS) have a large N{sub c} ''orientifold'' equivalence, provided charge conjugation symmetry is unbroken in the latter theory. Therefore, via a combined orbifold-orientifold mapping, a well-defined large N{sub c} equivalence exists between QCD(AS) in large, or infinite, volume and QCD(Adj) in arbitrarily small volume. Since asymptotically free gauge theories, such as QCD(Adj), are much easier to study (analytically or numerically) in small volume, this equivalence should allow greater understanding of large N{sub c} QCD in infinite volume.
Chiral random matrix theory and effective theories of QCD
Energy Technology Data Exchange (ETDEWEB)
Takahashi, K.; Iida, S
The correlations of the QCD Dirac eigenvalues are studied with use of an extended chiral random matrix model. The inclusion of spatial dependence which the original model lacks enables us to investigate the effects of diffusion modes. We get analytical expressions of level correlation functions with non-universal behavior caused by diffusion modes which is characterized by Thouless energy. Pion mode is shown to be responsible for these diffusion effects when QCD vacuum is considered a disordered medium.
Summary: Working Group on QCD and Strong Interactions
Energy Technology Data Exchange (ETDEWEB)
Edmond L. Berger et al.
In this summary of the considerations of the QCD working group at Snowmass 2001, the roles of quantum chromodynamics in the Standard Model and in the search for new physics are reviewed, with empahsis on frontier areas in the field. We discuss the importance of, and prospects for, precision QCD in perturbative and lattice calculations. We describe new ideas in the analysis of parton distribution functions and jet structure, and review progress in small-x and in polarization experiments.
Glueball and Meson Spectrum in Large- N QCD
Bochicchio, Marco
In the proceedings of HADRON 2015 we outlined a proposal for a string solution of large- N QCD, that is a candidate to satisfy fundamental properties such as the asymptotic freedom of the QCD S-matrix. Here we examine in more detail the implications for the large- N glueball and meson spectrum, that we compare with Particle Data Group (2015) and lattice gauge-theory computations at large N.
Holographic study of the QCD matter under external conditions
Directory of Open Access Journals (Sweden)
Katanaeva Alisa
We use methods of the bottom-up AdS/QCD approach to bring out the phase structure of several holographic models in which transition to a deconfined phase is related to a (first order Hawking-Page phase transition. The impact of phenomenological model parameters on the critical temperature and chemical potential is studied in detail. Comparison of the model predictions with results of experimental investigations, lattice QCD simulations and other methods is also done.
Threshold Corrections in Precision LHC Physics: QED otimes QCD
Ward, B F L; Jadach, Stanislaw; Yost, S A
With an eye toward LHC processes in which theoretical precisions of 1 percent are desired, we introduce the theory of the simultaneous YFS resummation of QED and QCD to compute the size of the expected resummed soft radiative threshold effects in precision studies of heavy particle production at the LHC. Our results show that both QED and QCD soft threshold effects must be controlled to be on the conservative side to achieve such precision goals.
Search for the QCD critical point at SPS energies
Anticic, T.; Barna, D.; Bartke, J.; Betev, L.; Bialkowska, H.; Blume, C.; Boimska, B.; Botje, M.; Bracinik, J.; Buncic, P.; Cerny, V.; Christakoglou, P.; Chung, P.; Chvala, O.; Cramer, J.G.; Csato, P.; Dinkelaker, P.; Eckardt, V.; Fodor, Z.; Foka, P.; Friese, V.; Gal, J.; Gazdzicki, M.; Genchev, V.; Gladysz, E.; Grebieszkow, K.; Hegyi, S.; Hohne, C.; Kadija, K.; Karev, A.; Kikola, D.; Kolesnikov, V.I.; Kornas, E.; Korus, R.; Kowalski, M.; Kreps, M.; Laszlo, A.; Lacey, R.; van Leeuwen, M.; Levai, P.; Litov, L.; Lungwitz, B.; Makariev, M.; Malakhov, A.I.; Mateev, M.; Melkumov, G.L.; Mischke, A.; Mitrovski, M.; Mrowczynski, St.; Palla, G.; Panagiotou, A.D.; Petridis, A.; Peryt, W.; Pikna, M.; Pluta, J.; Prindle, D.; Puhlhofer, F.; Renfordt, R.; Roland, C.; Roland, G.; Rybczynski, M.; Rybicki, A.; Sandoval, A.; Schmitz, N.; Schuster, T.; Seyboth, P.; Sikler, F.; Sitar, B.; Skrzypczak, E.; Slodkowski, M.; Stefanek, G.; Stock, R.; Strabel, C.; Strobele, H.; Susa, T.; Szentpetery, I.; Sziklai, J.; Szuba, M.; Szymanski, P.; Trubnikov, V.; Utvic, M.; Varga, D.; Vassiliou, M.; Veres, G.I.; Vesztergombi, G.; Vranic, D.; Wlodarczyk, Z.; Wojtaszek-Szwarc, A.; Yoo, I.K.; Abgrall, N.; Aduszkiewicz, A.; Andrieu, B.; Anticic, T.; Antoniou, N.; Argyriades, J.; Asryan, A.G.; Blondel, A.; Blumer, J.; Boldizsar, L.; Bravar, A.; Brzychczyk, J.; Bubak, A.; Bunyatov, S.A.; Choi, K.-U.; Chung, P.; Cleymans, J.; Derkach, D.A.; Diakonos, F.; Dominik, W.; Dumarchez, J.; Engel, R.; Ereditato, A.; Feofilov, G.A.; Ferrero, A.; Gazdzicki, M.; Golubeva, M.; Grzeszczuk, A.; Guber, F.; Hasegawa, T.; Haungs, A.; Igolkin, S.; Ivanov, A.S.; Ivashkin, A.; Katrynska, N.; Kielczewska, D.; Kisiel, J.; Kobayashi, T.; Kolev, D.; Kolevatov, R.S.; Kondratiev, V.P.; Kowalski, S.; Kurepin, A.; Lacey, R.; Lyubushkin, V.V.; Majka, Z.; Marchionni, A.; Marcinek, A.; Maris, I.; Matveev, V.; Meregaglia, A.; Messina, M.; Mijakowski, P.; Montaruli, T.; Murphy, S.; Nakadaira, T.; Naumenko, P.A.; Nikolic, V.; Nishikawa, K.; Palczewski, T.; Planeta, R.; Popov, B.A.; Posiadala, M.; Przewlocki, P.; Rauch, W.; Ravonel, M.; Rohrich, D.; Rondio, E.; Rossi, B.; Roth, M.; Rubbia, A.; Sadovsky, A.; Sakashita, K.; Sekiguchi, T.; Seyboth, P.; Shibata, M.; Sissakian, A.N.; Sorin, A.S.; Staszel, P.; Stepaniak, J.; Strabel, C.; Stroebele, H.; Tada, M.; Taranenko, A.; Tsenov, R.; Ulrich, R.; Unger, M.; Vechernin, V.V.; Zipper, W.
Lattice QCD calculations locate the QCD critical point at energies accessible at the CERN Super Proton Synchrotron (SPS). We present average transverse momentum and multiplicity fluctuations, as well as baryon and anti-baryon transverse mass spectra which are expected to be sensitive to effects of the critical point. The future CP search strategy of the NA61/SHINE experiment at the SPS is also discussed.
Instantons and quark zero modes in AdS/QCD
DEFF Research Database (Denmark)
Bechi, Jacopo
In this paper the quark zero modes creation effect is studied in the context of the AdS/QCD approach. This effect is generated, in presence of instantons, by a new that can be added in the bulk.......In this paper the quark zero modes creation effect is studied in the context of the AdS/QCD approach. This effect is generated, in presence of instantons, by a new that can be added in the bulk....
Strong couplings and form factors of charmed mesons in holographic QCD
Ballon-Bayona, Alfonso; Krein, Gastão; Miller, Carlisson
We extend the two-flavor hard-wall holographic model of Erlich, Katz, Son, and Stephanov [Phys. Rev. Lett. 95, 261602 (2005), 10.1103/PhysRevLett.95.261602] to four flavors to incorporate strange and charm quarks. The model incorporates chiral and flavor symmetry breaking and provides a reasonable description of masses and weak decay constants of a variety of scalar, pseudoscalar, vector, and axial-vector strange and charmed mesons. In particular, we examine flavor symmetry breaking in the strong couplings of the ρ meson to the charmed D and D* mesons. We also compute electromagnetic form factors of the π , ρ , K , K*, D and D* mesons. We compare our results for the D and D* mesons with lattice QCD data and other nonperturbative approaches.
Gauge invariant sub-structures of tree-level double-emission exact QCD spin amplitudes
Van Hameren, A
In this note we discuss possible separations of exact, massive, tree-level spin amplitudes into gauge invariant parts. We concentrate our attention on processes involving two quarks entering a color- neutral current and, thanks to the QCD interactions, two extra external gluons. We will search for forms compatible with parton shower languages, without applying approximations or restrictions on phase space regions. Special emphasis will be put on the isolation of parts necessary for the construction of evolution kernels for individual splittings and to some degree for the running coupling constant as well. Our aim is to better understand the environment necessary to optimally match hard matrix elements with partons shower algorithms. To avoid complications and ambiguities related to regularization schemes, we ignore, at this point, virtual corrections. Our representation is quite universal: any color-neutral current can be used, in particular our approach is not restricted to vector currents only.
High energy QCD at NLO: from light-cone wave function to JIMWLK evolution
Lublinsky, Michael; Mulian, Yair
Soft components of the light cone wave-function of a fast moving projectile hadron is computed in perturbation theory to the third order in QCD coupling constant. At this order, the Fock space of the soft modes consists of one-gluon, two-gluon, and a quark-antiquark states. The hard component of the wave-function acts as a non-Abelian background field for the soft modes and is represented by a valence charge distribution that accounts for non-linear density effects in the projectile. When scattered off a dense target, the diagonal element of the S-matrix reveals the Hamiltonian of high energy evolution, the JIMWLK Hamiltonian. This way we provide a new direct derivation of the JIMWLK Hamiltonian at the Next-to-Leading Order.
Analytic structure of QCD propagators in Minkowski space
Siringo, Fabio
Analytical functions for the propagators of QCD, including a set of chiral quarks, are derived by a one-loop massive expansion in the Landau gauge, deep in the infrared. By analytic continuation, the spectral functions are studied in Minkowski space, yielding a direct proof of positivity violation and confinement from first principles. The dynamical breaking of chiral symmetry is described on the same footing of gluon mass generation, providing a unified picture. While dealing with the exact Lagrangian, the expansion is based on massive free-particle propagators, is safe in the infrared and is equivalent to the standard perturbation theory in the UV. By dimensional regularization, all diverging mass terms cancel exactly without including mass counterterms that would spoil the gauge and chiral symmetry of the Lagrangian. Universal scaling properties are predicted for the inverse dressing functions and shown to be satisfied by the lattice data. Complex conjugated poles are found for the gluon propagator, in agreement with the i-particle scenario.
Impact of water hardness on energy consumption of geyser heating ...
African Journals Online (AJOL)
water hardness as a chemical parameter that may impact the power consumption of electrical geyser heating elements. An accelerated scaling .... pictures of the geyser heating elements tested are shown in Fig. 1. Water hardness meters .... The aim of heating cycle and temperature experiments was to show whether scaling ...
Tests of QCD factorisation in the diffractive production of dijets in deep-inelastic scattering and photoproduction at HERA
Energy Technology Data Exchange (ETDEWEB)
Aktas, A. [DESY, Hamburg (Germany); Andreev, V. [Lebedev Physical Instiute, Moscow (Russian Federation); Anthonis, T. [Inter-Univ. Institute for High Energies ULB-VUB, Brussels (Belgium)]|[Antwerpen Univ. (BE)] (and others)
Measurements are presented of differential dijet cross sections in diffractive photoproduction (Q{sup 2} < 0.01 GeV{sup 2}) and deep-inelastic scattering processes (DIS, 4 < Q{sup 2} < 80 GeV{sup 2}). The event topology is given by ep {yields} eXY, in which the system X, containing at least two jets, is separated from a leading low-mass proton remnant system Y by a large rapidity gap. The dijet cross sections are compared with NLO QCD predictions based on diffractive parton densities previously obtained from a QCD analysis of inclusive diffractive DIS cross sections by H1. In DIS, the dijet data are well described, supporting the validity of QCD factorisation. The diffractive DIS dijet data are more sensitive to the diffractive gluon density at high fractional parton momentum than the measurements of inclusive diffractive DIS. In photoproduction, the predicted dijet cross section has to be multiplied by a factor of approximately 0.5 for both direct and resolved photon interactions to describe the measurements. The ratio of measured dijet cross section to NLO prediction in photoproduction is a factor 0.5 {+-} 0.1 smaller than the same ratio in DIS. This suppression is the first clear observation of QCD hard scattering factorisation breaking at HERA. The measurements are also compared to the two soft colour neutralisation models SCI and GAL. The SCI model describes diffractive dijet production in DIS but not in photoproduction. The GAL model fails in both kinematic regions. (orig.)
Perturbative QCD versus pion exchange and hadronic FSI effects in the {gamma}{gamma}{yields}{pi}{sup +}{pi}{sup -} reaction
Energy Technology Data Exchange (ETDEWEB)
Szczurek, A. E-mail: firstname.lastname@example.com; Speth, J
The interplay of pQCD, pion exchange and FSI effects is studied for the {gamma}{gamma}{yields}{pi}{sup +}{pi}{sup -} reaction in the region of 2 GeV
"The second international conference on hard and electromagnetic probes of high-energy nuclear collisions was held June 9 to 16, 2006 at the Asilomar Conference grounds in Pacific Grove, California" (photo and 1/2 page)
Directory of Open Access Journals (Sweden)
Ronald W. Armstrong
Full Text Available There is expanded interest in the long-standing subject of the hardness properties of materials. A major part of such interest is due to the advent of nanoindentation hardness testing systems which have made available orders of magnitude increases in load and displacement measuring capabilities achieved in a continuously recorded test procedure. The new results have been smoothly merged with other advances in conventional hardness testing and with parallel developments in improved model descriptions of both elastic contact mechanics and dislocation mechanisms operative in the understanding of crystal plasticity and fracturing behaviors. No crystal is either too soft or too hard to prevent the determination of its elastic, plastic and cracking properties under a suitable probing indenter. A sampling of the wealth of measurements and reported analyses associated with the topic on a wide variety of materials are presented in the current Special Issue.
Phenomenological study of the Bc→BP, BV decays with perturbative QCD approach
Sun, Junfeng; Yang, Yueling; Chang, Qin; Lu, Gongru
Inspired by the recent LHCb measurements and forthcoming great potential on Bc meson, we study the exclusive Bc→BqP, BqV decays with the perturbative QCD approach, where q =u, d, s and P and V denote the lightest pseudoscalar and vector SU(3) nonet meson, respectively. By retaining the quark transverse momentum, employing the Sudakov factors, and choosing the typical scale as the maximum virtualities of the internal particles, we calculate the Bc→B transition from factors, and our results show that about 90% of the contribution to form factors comes from the αs/π running LHCb.
Charm quark mass and D-meson decay constants from two-flavour lattice QCD
Heitger, Jochen; Schaefer, Stefan; Virotta, Francesco
We present a computation of the charm quark's mass and the leptonic D-meson decay constants f_D and f_{D_s} in two-flavour lattice QCD with non-perturbatively O(a) improved Wilson quarks. Our analysis is based on the CLS configurations at two lattice spacings (a=0.065 and 0.048 fm, where the lattice scale is set by f_K) and pion masses ranging down to ~ 190 MeV at L*m_pi > 4, in order to perform controlled continuum and chiral extrapolations with small systematic uncertainties.
Chiral Imbalance in QCD and its consequences
Directory of Open Access Journals (Sweden)
Andrianov Alexander
Full Text Available Under extreme conditions of high temperature and/or large quark (baryon density, the vacuum of QCD changes its properties, and deconfinement, chiral symmetry restoration as well as chiral symmetry breaking take place. These transitions (phases are accompanied by the rapid change in the rate and nature of topological transitions connecting different topological sectors. The heavy ion collisions (HIC program opens a possibility to study these phenomena in so-called non-Abelian Quark-gluon plasma (QGP. In these phases the currents of light quarks (vector and axial-vector can be independently examined for right-handed (RH and left-handed (LH quarks. To describe such a quark matter chiral chemical potential can be introduced to quantify the presence of chirality imbalance (ChI i.e. the difference between the average numbers of RH and LH quarks in the fireball after HIC. In this review talk we will focus our attention on the discussion of the ChI related developments in heavy ion physics at central collisions and the plans for the future experiments aimed at establishing (or falsifying the presence of Local spacial Parity Breaking (LPB in heavy ion data. We describe some of experimental observables in detecting the signal of LPB. A number of measurements is proposed that allow to reach a definite conclusion on the occurrence of LPB effects in non-Abelian QGP produced in central heavy ion collisions and its simulation within a number of QCD-inspired models is outlined. Based on the effective meson theory in the presence of Chern-Simons interaction it is found that the spectrum of massive vector mesons splits into three polarization components with different effective masses. Moreover a resonance broadening occurs that leads to an increase of spectral contribution to the dilepton production as compared to the vacuum state. The asymmetry in production of longitudinally and transversely polarized states of ρ and ω mesons for various values of the
Dark-matter QCD-axion searches.
Rosenberg, Leslie J
In the late 20th century, cosmology became a precision science. Now, at the beginning of the next century, the parameters describing how our universe evolved from the Big Bang are generally known to a few percent. One key parameter is the total mass density of the universe. Normal matter constitutes only a small fraction of the total mass density. Observations suggest this additional mass, the dark matter, is cold (that is, moving nonrelativistically in the early universe) and interacts feebly if at all with normal matter and radiation. There's no known such elementary particle, so the strong presumption is the dark matter consists of particle relics of a new kind left over from the Big Bang. One of the most important questions in science is the nature of this dark matter. One attractive particle dark-matter candidate is the axion. The axion is a hypothetical elementary particle arising in a simple and elegant extension to the standard model of particle physics that nulls otherwise observable CP-violating effects (where CP is the product of charge reversal C and parity inversion P) in quantum chromo dynamics (QCD). A light axion of mass 10(-(6-3)) eV (the invisible axion) would couple extraordinarily weakly to normal matter and radiation and would therefore be extremely difficult to detect in the laboratory. However, such an axion is a compelling dark-matter candidate and is therefore a target of a number of searches. Compared with other particle dark-matter candidates, the plausible range of axion dark-matter couplings and masses is narrowly constrained. This focused search range allows for definitive searches, where a nonobservation would seriously impugn the dark-matter QCD-axion hypothesis. Axion searches use a wide range of technologies, and the experiment sensitivities are now reaching likely dark-matter axion couplings and masses. This article is a selective overview of the current generation of sensitive axion searches. Not all techniques and experiments
The advent of finite temperature lattice QCD in 1980 confirmed that hot strongly interacting matter will be transformed into a new medium of deconfined quarks and gluons, the primordial quark-gluon plasma. It was thus natural to see if this state of the early universe could somehow still be produced today, in terrestrial laboratories. An experimental program based on high energy nuclear collisions was developed at a meeting which Maurice Jacob and I convened in Bielefeld in 1982, and in the mid-eighties the planning and construction of "heavy ion experiments" was well underway both at CERN and at Brookhaven. At the 1987 Quark Matter Meeting in Nordkirchen/Germany, the first results were reported.
Hardness amplification in nondeterministic logspace
Gupta, Sushmita
A hard problem is one which cannot be easily computed by efficient algorithms. Hardness amplification is a procedure which takes as input a problem of mild hardness and returns a problem of higher hardness. This is closely related to the task of decoding certain error-correcting codes. We show amplification from mild average case hardness to higher average case hardness for nondeterministic logspace and worst-to-average amplification for nondeterministic linspace. Finally we explore possible ...
Hard exclusive neutrino production of a light meson
Pire, B.; Szymanowski, L.; Wagner, J.
We update the leading order in αs QCD amplitude for deep exclusive neutrino and antineutrino production of a light meson on an unpolarized nucleon. The factorization theorems of the collinear QCD approach allow us to write the amplitude as the convolution of generalized parton distributions and perturbatively calculable coefficient functions. We study both the pseudoscalar-meson and longitudinally polarized vector-meson cases. It turns out that, contrarily to the electroproduction case, the leading-twist scattering amplitudes for π and ρL productions are proportional to one another, which may serve as an interesting new test of the leading-twist dominance of exclusive processes at medium scale. The importance of the gluonic contribution to most cross sections is stressed.
Hard and soft acids and bases: atoms and atomic ions.
Reed, James L
The structural origin of hard-soft behavior in atomic acids and bases has been explored using a simple orbital model. The Pearson principle of hard and soft acids and bases has been taken to be the defining statement about hard-soft behavior and as a definition of chemical hardness. There are a number of conditions that are imposed on any candidate structure and associated property by the Pearson principle, which have been exploited. The Pearson principle itself has been used to generate a thermodynamically based scale of relative hardness and softness for acids and bases (operational chemical hardness), and a modified Slater model has been used to discern the electronic origin of hard-soft behavior. Whereas chemical hardness is a chemical property of an acid or base and the operational chemical hardness is an experimental measure of it, the absolute hardness is a physical property of an atom or molecule. A critical examination of chemical hardness, which has been based on a more rigorous application of the Pearson principle and the availability of quantitative measures of chemical hardness, suggests that the origin of hard-soft behavior for both acids and bases resides in the relaxation of the electrons not undergoing transfer during the acid-base interaction. Furthermore, the results suggest that the absolute hardness should not be taken as synonymous with chemical hardness but that the relationship is somewhat more complex. Finally, this work provides additional groundwork for a better understanding of chemical hardness that will inform the understanding of hardness in molecules.
QCD inspired bag model of quarkonium
Hasenfratz, Peter; Kuti, Julius; Richard, J M
The QCD motivated bag model is applied to heavy quark-antiquark systems. The effect of colored glue in the model is shown to explain the rapid cross-over of the static QQ potential from the asymptotically free Coulomb region into the linear confinement regime. The spin-dependent force between static quarks is derived in Coulomb gauge from the exchange of a confined transverse gluon. The dimensional bag parameter Lambda /sub B/=235 MeV and the quark-gluon coupling constant alpha =0.38 as defined at r/sub QQ/ approximately 0.2 fermi are determined from a good fit of the cc and bb spectra. The fit is in serious disagreement with the widely accepted MIT parameters. As an important test of their model, the authors calculate the rich spectrum of QQ glue states. In Upsilon particle spectroscopy they predict a narrow QQglue state with exotic quantum numbers J/sup PC/=1/sup -+/ below the BB threshold. Its experimental confirmation would be the first direct evidence for colored glue in the hadron spectrum. (3 refs).
The transverse structure of the QCD string
Meyer, Harvey B
The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is the appropriate probe to use when comparing with the next-to-leading order string prediction. Secondly we derive the constraints imposed by open-closed string duality on the transverse structure of the string. We show that a total of three independent `gravitational' form factors characterize the transverse profile of the closed string, and obtain the interpretation of recent ef...
QCD tests with SLD and polarized beams
Energy Technology Data Exchange (ETDEWEB)
Strauss, M.G. [Univ. of Massachusetts, Amherst, MA (United States)
The author presents a measurement of the strong coupling {alpha}{sub s} derived from multijet rates using data collected by the SLD experiment at SLAC and find that {alpha}{sub s}(M{sub Z}{sup 2}) = 0.118 {+-} 0.002(stat.) {+-} 0.003(syst.) {+-} 0.010(theory). He presents tests of the flavor independence of strong interactions via preliminary measurements of the ratios {alpha}{sub s}(b)/{alpha}{sub s}(udsc) and {alpha}{sub s}(uds)/{alpha}{sub s}(bc). In addition, the group has measured the difference in charged particle multiplicity between Z{sup 0} {yields} b{bar b} and Z{sup 0} {yields} u{bar u}, d{bar d}, s{bar s} events, and find that it supports the prediction of perturbative QCD that the multiplicity difference be independent of center-of-mass energy. Finally, the group has made a preliminary study of jet polarization using the jet handedness technique.
Hydrodynamic excitations in hot QCD plasma
Abbasi, Navid; Allahbakhshi, Davood; Davody, Ali; Taghavi, Seyed Farid
We study the long wavelength excitations in rotating QCD fluid in the presence of an external magnetic field at finite vector and axial charge densities. We consider the fluctuations of vector and axial charge currents coupled to energy and momentum fluctuations and compute the S O (3 ) covariant dispersion relations of the six corresponding hydrodynamic modes. Among them, there are always two scalar chiral-magnetic-vortical-heat (CMVH) waves; in the absence of a magnetic field (vorticity) these waves reduce to chiral-vortical-heat (CVH) [chiral-magnetic-heat (CMH)] waves. While CMVH waves are a mixture of CMH and CVH waves, they have generally different velocities compared to the sum of velocities of the latter waves. The other four modes, which are made out of scalar-vector fluctuations, are mixed sound-Alfvén waves. We show that when the magnetic field is parallel with the vorticity, these four modes are the two ordinary sound modes together with two chiral Alfvén waves propagating along the common direction of the magnetic field and vorticity.
Conformal Properties in High Temperature QCD
Ishikawa, K -I; Nakayama, Yu; Yoshie, T
We investigate the properties of quarks and gluons above the chiral phase transition temperature $T_c,$ using the RG improved gauge action and the Wilson quark action with two degenerate quarks mainly on a $32^3\\times 16$ lattice. In the one-loop perturbation theory, the thermal ensemble is dominated by the gauge configurations with effectively $Z(3)$ center twisted boundary conditions, making the thermal expectation value of the spatial Polyakov loop take a non-trivial $Z(3)$ center. This is in agreement with our lattice simulation of high temperature QCD. We further observe that the temporal propagator of massless quarks at extremely high temperature $\\beta=100.0 \\, (T \\simeq10^{58} T_c)$ remarkably agrees with the temporal propagator of free quarks with the $Z(3)$ twisted boundary condition for $t/L_t \\geq 0.2$, but differs from that with the $Z(3)$ trivial boundary condition. As we increase the mass of quarks $m_q$, we find that the thermal ensemble continues to be dominated by the $Z(3)$ twisted gauge fi...
Deep Inelastic Scattering in Conformal QCD
Cornalba, Lorenzo; Penedones, Joao
We consider the Regge limit of a CFT correlation function of two vector and two scalar operators, as appropriate to study small-x deep inelastic scattering in N=4 SYM or in QCD assuming approximate conformal symmetry. After clarifying the nature of the Regge limit for a CFT correlator, we use its conformal partial wave expansion to obtain an impact parameter representation encoding the exchange of a spin j Reggeon for any value of the coupling constant. The CFT impact parameter space is the three-dimensional hyperbolic space H3, which is the impact parameter space for high energy scattering in the dual AdS space. We determine the small-x structure functions associated to the exchange of a Reggeon. We discuss unitarization from the point of view of scattering in AdS and comment on the validity of the eikonal approximation. We then focus on the weak coupling limit of the theory where the amplitude is dominated by the exchange of the BFKL pomeron. Conformal invariance fixes the form of the vector impact factor a...
One-dimensional QCD in thimble regularization
Di Renzo, F.; Eruzzi, G.
QCD in 0 +1 dimensions is numerically solved via thimble regularization. In the context of this toy model, a general formalism is presented for S U (N ) theories. The sign problem that the theory displays is a genuine one, stemming from a (quark) chemical potential. Three stationary points are present in the original (real) domain of integration, so that contributions from all the thimbles associated to them are to be taken into account: we show how semiclassical computations can provide hints on the regions of parameter space where this is absolutely crucial. Known analytical results for the chiral condensate and the Polyakov loop are correctly reproduced: this is in particular trivial at high values of the number of flavors Nf. In this regime we notice that the single thimble dominance scenario takes place (the dominant thimble is the one associated to the identity). At low values of Nf computations can be more difficult. It is important to stress that this is not at all a consequence of the original sign problem (not even via the residual phase). The latter is always under control, while accidental, delicate cancelations of contributions coming from different thimbles can be in place in (restricted) regions of the parameter space.
QCD perturbation theory in the temporal gauge
Leroy, J. P.; Micheli, J.; Rossi, G. C.; Yoshida, K.
In this paper we present a non-trivial check of the consistency of the quantization of a gauge theory with fermions (QCD) in the temporal gauge. We use the approach based on the finite time Feynman propagation kernel, in which the Gauss law is imposed as a constraint on the states by means of a functional integration over all the time independent gauge transformations acting on the boundary values of the fields. We spell out in detail the "Feynman rules" when fermions are present and we compute, as an example, the gauge invariant correlation function 10052_2005_Article_BF01614701_TeX2GIFE1.gif begin{gathered} G(t) = left< {bar ψ (0,t)(γ _5 γ _0 ){1 - γ _0 }/2P} right. \\ left. { \\cdot exp left( {igintlimits_0^t {A_0 (0,t')dt'} } right)(γ _5 γ _0 )^ + (0,0)} rightrangle \\ up to order g 2, obtaining the expected result.
Color-Kinematics Duality for QCD Amplitudes
Johansson, Henrik
We show that color-kinematics duality is present in tree-level amplitudes of quantum chromodynamics with massive flavored quarks. Starting with the color structure of QCD, we work out a new color decomposition for n-point tree amplitudes in a reduced basis of primitive amplitudes. These primitives, with k quark-antiquark pairs and (n-2k) gluons, are taken in the (n-2)!/k! Melia basis, and are independent under the color-algebra Kleiss-Kuijf relations. This generalizes the color decomposition of Del Duca, Dixon, and Maltoni to an arbitrary number of quarks. The color coefficients in the new decomposition are given by compact expressions valid for arbitrary gauge group and representation. Considering the kinematic structure, we show through explicit calculations that color-kinematics duality holds for amplitudes with general configurations of gluons and massive quarks. The new (massive) amplitude relations that follow from the duality can be mapped to a well-defined subset of the familiar BCJ relations for gluo...
AdS/QCD, LIight-Front Holography, and the Non-perturbative Running Coupling
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC; de Teramond, Guy; /Costa Rica U.; Deur, Alexandre; /Jefferson Lab
The combination of Anti-de Sitter space (AdS) methods with light-front (LF) holography provides a remarkably accurate first approximation for the spectra and wavefunctions of meson and baryon light-quark bound states. The resulting bound-state Hamiltonian equation of motion in QCD leads to relativistic light-front wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. These equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-J modes in anti-de Sitter (AdS) space. The eigenvalues give the hadronic spectrum, and the eigenmodes represent the probability distributions of the hadronic constituents at a given scale. A positive-sign confining dilaton background modifying AdS space gives a very good account of meson and baryon spectroscopy and form factors. The light-front holographic mapping of this model also leads to a non-perturbative effective coupling {alpha}{sub s}{sup Ads} (Q{sup 2}) which agrees with the effective charge defined by the Bjorken sum rule and lattice simulations. It displays a transition from perturbative to nonperturbative conformal regimes at a momentum scale {approx} 1 GeV. The resulting {beta}-function appears to capture the essential characteristics of the full {beta}-function of QCD, thus giving further support to the application of the gauge/gravity duality to the confining dynamics of strongly coupled QCD.
Dilepton Spectroscopy of QCD Matter at Collider Energies
Directory of Open Access Journals (Sweden)
Ralf Rapp
Full Text Available Low-mass dilepton spectra as measured in high-energy heavy-ion collisions are a unique tool to obtain spectroscopic information about the strongly interacting medium produced in these reactions. Specifically, in-medium modifications of the vector spectral function, which is well known in the vacuum, can be deduced from the thermal radiation off the expanding QCD fireball. This, in particular, allows to investigate the fate of the ρ resonance in the dense medium and possibly infer from it signatures of the (partial restoration of chiral symmetry, which is spontaneously broken in the QCD vacuum. After briefly reviewing calculations of thermal dilepton emission rates from hot QCD matter, utilizing effective hadronic theory, lattice QCD, or resummed perturbative QCD, we focus on applications to dilepton spectra at heavy-ion collider experiments at RHIC and LHC. This includes invariant-mass spectra at full RHIC energy with transverse-momentum dependencies and azimuthal asymmetries, as well as a systematic investigation of the excitation function down to fixed-target energies, thus making contact to previous precision measurements at the SPS. Furthermore, predictions for the energy frontier at the LHC are presented in both dielectron and dimuon channels.
Chen, Xiao-Jia; Struzhkin, Viktor V.; Wu, Zhigang; Somayazulu, Maddury; Qian, Jiang; Kung, Simon; Christensen, Axel Nørlund; Zhao, Yusheng; Cohen, Ronald E.; Mao, Ho-kwang; Hemley, Russell J.
Detailed study of the equation of state, elasticity, and hardness of selected superconducting transition-metal nitrides reveals interesting correlations among their physical properties. Both the bulk modulus and Vickers hardness are found to decrease with increasing zero-pressure volume in NbN, HfN, and ZrN. The computed elastic constants from first principles satisfy c11 > c12 > c44 for NbN, but c11 > c44 > c12 for HfN and ZrN, which are in good agreement with the neutron scattering data. The cubic δ-NbN superconducting phase possesses a bulk modulus of 348 GPa, comparable to that of cubic boron nitride, and a Vickers hardness of 20 GPa, which is close to sapphire. Theoretical calculations for NbN show that all elastic moduli increase monotonically with increasing pressure. These results suggest technological applications of such materials in extreme environments. PMID:15728352
Session: Hard Rock Penetration
Energy Technology Data Exchange (ETDEWEB)
Tennyson, George P. Jr.; Dunn, James C.; Drumheller, Douglas S.; Glowka, David A.; Lysne, Peter
This session at the Geothermal Energy Program Review X: Geothermal Energy and the Utility Market consisted of five presentations: ''Hard Rock Penetration - Summary'' by George P. Tennyson, Jr.; ''Overview - Hard Rock Penetration'' by James C. Dunn; ''An Overview of Acoustic Telemetry'' by Douglas S. Drumheller; ''Lost Circulation Technology Development Status'' by David A. Glowka; ''Downhole Memory-Logging Tools'' by Peter Lysne.
CERN will be organizing a special information day on Friday, 27th June, designed to promote the wearing of hard hats and ensure that they are worn correctly. A new prevention campaign will also be launched.The event will take place in the hall of the Main Building from 11.30 a.m. to 2.00 p.m., when you will be able to come and try on various models of hard hat, including some of the very latest innovative designs, ask questions and pass on any comments and suggestions.
Non-perturbative running of quark masses in three-flavour QCD
Campos, Isabel; Pena, Carlos; Preti, David; Ramos, Alberto; Vladikas, Anastassios
We present our preliminary results for the computation of the non-perturbative running of renormalized quark masses in $N_f = 3$ QCD, between the electroweak and hadronic scales, using standard finite-size scaling techniques. The computation is carried out to very high precision, using massless $\\mathcal{O}(a)$-improved Wilson quarks. Following the strategy adopted by the ALPHA Collaboration for the running coupling, different schemes are used above and below a scale $\\mu_0 \\sim m_b$, which differ by using either the Schr\\"odinger Functional or Gradient Flow renormalized coupling. We discuss our results for the running in both regions, and the procedure to match the two schemes.
The relation between random matrix theory, chiral perturbation theory and lattice-QCD; Die Beziehungen zwischen Random-Matrix-Theorie, chiraler Stoerungstheorie und Gitter-QCD
Energy Technology Data Exchange (ETDEWEB)
Hehl, H.
This thesis has studied the range of validity of the chiral random matrix theory in QCD on the example of the quenched staggered Dirac operator. The eigenvalues of this operator in the neighbourhood of zero are essential for the understanding of the spontaneous breaking of the chiral symmetry and the phase transition connected with this. The phase transition cannot be understood in the framework of perturbation theory, so that the formulation of QCD on the lattice has been chosen as the only non-perturbative approach. In order to circumvent both the problem of the fermion doubling and to study chiral properties on the lattice with acceptable numerical effort, quenched Kogut-Susskind fermions have been applied. The corresponding Dirac operator can be completely diagonalized by the Lanczos procedure of Cullum and Willoughby. Monte carlo simulations on hypercubic lattice have been performed and the Dirac operators of very much configurations diagonalized at different lattice lengths and coupling constants. The eigenvalue correlations on the microscopic scale are completely described by the chiral random matrix theory for the topological sector zero, which has been studied by means of the distribution of the smallest eigenvalue, the microscopic spectral density and the corresponding 2-point correlation function. The found universal behaviour shows, that on the scale of the lowest eigenvalue only completely general properties of the theory are important, but not the full dynamics. In order to determine the energy scale, from which the chiral random matrix theory losses its validity, - the Thouless energy - with the scalar susceptibilities observables have been analyzed, which are because of their spectral mass dependence sensitive on this. For each combination of the lattice parameter so the deviation point has been identified.
QCD analysis of neutral and charged current cross sections and search for contact interactions at HERA
Energy Technology Data Exchange (ETDEWEB)
Pirumov, Hayk
A QCD analysis of the inclusive deep inelastic ep scattering cross section measured by the H1 experiment at HERA is presented. The data correspond to a total integrated luminosity of about 0.5 fb{sup -1} and covers a kinematic range of 0.5 GeV{sup 2} - 30000 GeV{sup 2} in the negative four-momentum transfer Q{sup 2} and 3 . 10{sup -5} - 0.65 in Bjorken x. The performed QCD analysis of the double differential neutral and charged current cross sections results in a set of parton distribution functions H1PDF 2012. The precise data from HERA II period in the kinematic region of high Q{sup 2} considerably improve the accuracy of the PDFs at the high x. In addition a search for signs of new physics using single differential neutral current cross section measurements at high Q{sup 2} is performed. The observed good agreement of the analysed data with the Standard Model predictions allows to set constraints on various new physics models within the framework of contact interactions. Limits are derived on the compositeness scale for general contact interactions, on the ratio of mass to the Yukawa coupling for heavy leptoquark models, on the effective Plank-mass scale in the large extra dimension models and on the quark radius.
Top-pair production at the LHC through NNLO QCD and NLO EW
Czakon, Michał; Heymes, David; Mitov, Alexander; Pagani, Davide; Tsinikos, Ioannis; Zaro, Marco
In this work we present for the first time predictions for top-quark pair differential distributions at the LHC at NNLO QCD accuracy and including EW corrections. For the latter we include not only contributions of O({α}_s^2α ) , but also those of order O({α}_s{α}^2) and O({α}^3) . Besides providing phenomenological predictions for all main differential distributions with stable top quarks, we also study the following issues. 1) The effect of the photon PDF on top-pair spectra: we find it to be strongly dependent on the PDF set used — especially for the top p T distribution. 2) The difference between the additive and multiplicative approaches for combining QCD and EW corrections: with our scale choice, we find relatively small differences between the central predictions, but reduced scale dependence within the multiplicative approach. 3) The potential effect from the radiation of heavy bosons on inclusive top-pair spectra: we find it to be, typically, negligible.
Aspects of perturbative QCD at a 100 TeV future hadron collider
Bothmann, Enrico; Ferrarese, Piero; Krauss, Frank; Kuttimalai, Silvan; Schumann, Steffen; Thompson, Jennifer
In this paper we consider particle production at a future circular hadron collider with 100 TeV center-of-mass energy within the Standard Model, and in particular their QCD aspects. Accurate predictions for these processes pose severe theoretical challenges related to large hierarchies of scales and possible large multiplicities of final-state particles. We investigate scaling patterns in multijet-production rates allowing to extrapolate predictions to very high final-state multiplicities. Furthermore, we consider large-area QCD jets and study the expectation for the mean number of subjets to be reconstructed from their constituents and confront these with analytical resummed predictions and with the expectation for boosted hadronic decays of top quarks and W bosons. We also discuss the validity of Higgs effective field theory in making predictions for Higgs-boson production in association with jets. Finally, we consider the case of new physics searches at such a 100 TeV hadron-collider machine and discuss the expectations for corresponding Standard-Model background processes.
Search for the pentaquark resonance signature in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
B. G. Lasscock; J. Hedditch; D. B. Leinweber; W. Melnitchouk; A. W. Thomas; A. G. Williams; R. D. Young; J. M. Zanotti
Claims concerning the possible discovery of the $\\Theta^+$ pentaquark, with minimal quark content $uudd\\bar{s}$, have motivated our comprehensive study into possible pentaquark states using lattice QCD. We review various pentaquark interpolating fields in the literature and create a new candidate ideal for lattice QCD simulations. Using these interpolating fields we attempt to isolate a signal for a five-quark resonance. Calculations are performed using improved actions on a large $20^{3} \\times 40$ lattice in the quenched approximation. The standard lattice resonance signal of increasing attraction between baryon constituents for increasing quark mass is not observed for spin-1/2 pentaquark states. We conclude that evidence supporting the existence of a spin-1/2 pentaquark resonance does not exist in quenched QCD.
Electroweak Higgs production with HiggsPO at NLO QCD
Greljo, Admir; Isidori, Gino; Lindert, Jonas M.; Marzocca, David; Zhang, Hantian
We present the HiggsPO UFO model for Monte Carlo event generation of electroweak VH and VBF Higgs production processes at NLO in QCD in the formalism of Higgs pseudo-observables (PO). We illustrate the use of this tool by studying the QCD corrections, matched to a parton shower, for several benchmark points in the Higgs PO parameter space. We find that, while being sizable and thus important to be considered in realistic experimental analyses, the QCD higher-order corrections largely factorize. As an additional finding, based on the NLO results, we advocate to consider 2D distributions of the two-jet azimuthal-angle difference and the leading jet p_T for new physics searches in VBF Higgs production. The HiggsPO UFO model is publicly available.
The High Energy Asymptotics of Scattering Processes in QCD
Energy Technology Data Exchange (ETDEWEB)
Enberg, Rikard; Golec-Biernat, K.; Munier, S.
High energy scattering in the QCD parton model was recently shown to be a reaction-diffusion process, and thus to lie in the universality class of the stochastic Fisher-Kolmogorov-Petrovsky-Piscounov equation. We recall that the latter appears naturally in the context of the parton model. We provide a thorough numerical analysis of the mean field approximation, given in QCD by the Balitsky-Kovchegov equation. In the framework of a simple stochastic toy model that captures the relevant features of QCD, we discuss and illustrate the universal properties of such stochastic models. We investigate in particular the validity of the mean field approximation and how it is broken by fluctuations. We find that the mean field approximation is a good approximation in the initial stages of the evolution in rapidity.
Light-Front Holography: A First Approximation to QCD
Energy Technology Data Exchange (ETDEWEB)
de Teramond, Guy F.; Brodsky, Stanley J.
Starting from the Hamiltonian equation of motion in QCD, we identify an invariant light-front coordinate {zeta} which allows the separation of the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single variable light-front Schroedinger equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. This light-front wave equation is equivalent to the equations of motion which describe the propagation of spin-J modes on anti-de Sitter (AdS) space. This allows us to establish formally a gauge/gravity correspondence between an effective gravity theory defined on AdS5 and light front QCD.
Two-loop QCD corrections to Bc meson leptonic decays
Directory of Open Access Journals (Sweden)
Long-Bin Chen
Full Text Available The two-loop quantum chromodynamics (QCD radiative corrections to the Bc meson leptonic decay rate are calculated in the framework of the non-relativistic QCD (NRQCD factorization formalism. Two types of master integrals appearing in the calculation are obtained analytically for the first time. We calculate the short-distance coefficient of the leading matrix element to order αs2 by matching the full perturbative QCD calculation results to the corresponding NRQCD results. The result presented in this work helps the evaluation of both the Bc leptonic decay constant and the Cabibbo–Kobayashi–Maskawa (CKM matrix element |Vcb| to the full next-to-next-to-leading-order (NNLO degree of accuracy.
Exposing the QCD Splitting Function with CMS Open Data
Larkoski, Andrew; Marzani, Simone; Thaler, Jesse; Tripathee, Aashish; Xue, Wei
The splitting function is a universal property of quantum chromodynamics (QCD) which describes how energy is shared between partons. Despite its ubiquitous appearance in many QCD calculations, the splitting function cannot be measured directly, since it always appears multiplied by a collinear singularity factor. Recently, however, a new jet substructure observable was introduced which asymptotes to the splitting function for sufficiently high jet energies. This provides a way to expose the splitting function through jet substructure measurements at the Large Hadron Collider. In this Letter, we use public data released by the CMS experiment to study the two-prong substructure of jets and test the 1 →2 splitting function of QCD. To our knowledge, this is the first ever physics analysis based on the CMS Open Data.
QCD equation of state to O (μB6) from lattice QCD
Bazavov, A.; Ding, H.-T.; Hegde, P.; Kaczmarek, O.; Karsch, F.; Laermann, E.; Maezawa, Y.; Mukherjee, Swagato; Ohno, H.; Petreczky, P.; Sandmeyer, H.; Steinbrecher, P.; Schmidt, C.; Sharma, S.; Soeldner, W.; Wagner, M.
We calculated the QCD equation of state using Taylor expansions that include contributions from up to sixth order in the baryon, strangeness and electric charge chemical potentials. Calculations have been performed with the Highly Improved Staggered Quark action in the temperature range T ∈[135 MeV ,330 MeV ] using up to four different sets of lattice cutoffs corresponding to lattices of size Nσ3×Nτ with aspect ratio Nσ/Nτ=4 and Nτ=6 - 16 . The strange quark mass is tuned to its physical value, and we use two strange to light quark mass ratios ms/ml=20 and 27, which in the continuum limit correspond to a pion mass of about 160 and 140 MeV, respectively. Sixth-order results for Taylor expansion coefficients are used to estimate truncation errors of the fourth-order expansion. We show that truncation errors are small for baryon chemical potentials less then twice the temperature (μB≤2 T ). The fourth-order equation of state thus is suitable for the modeling of dense matter created in heavy ion collisions with center-of-mass energies down to √{sN N}˜12 GeV . We provide a parametrization of basic thermodynamic quantities that can be readily used in hydrodynamic simulation codes. The results on up to sixth-order expansion coefficients of bulk thermodynamics are used for the calculation of lines of constant pressure, energy and entropy densities in the T -μB plane and are compared with the crossover line for the QCD chiral transition as well as with experimental results on freeze-out parameters in heavy ion collisions. These coefficients also provide estimates for the location of a possible critical point. We argue that results on sixth-order expansion coefficients disfavor the existence of a critical point in the QCD phase diagram for μB/T ≤2 and T /Tc(μB=0 )>0.9 .
Universality of transverse-momentum resummation and hard factors at the NNLO
Energy Technology Data Exchange (ETDEWEB)
Catani, Stefano [INFN, Sezione di Firenze and Dipartimento di Fisica e Astronomia, Università di Firenze, I-50019 Sesto Fiorentino, Florence (Italy); Cieri, Leandro [Dipartimento di Fisica, Università di Roma "La Sapienza" and INFN, Sezione di Roma, I-00185 Rome (Italy); Florian, Daniel de [Departamento de Física, FCEYN, Universidad de Buenos Aires, (1428) Pabellón 1 Ciudad Universitaria, Capital Federal (Argentina); Ferrera, Giancarlo [Dipartimento di Fisica, Università di Milano and INFN, Sezione di Milano, I-20133 Milan (Italy); Grazzini, Massimiliano [Institut für Theoretische Physik, Universität Zürich, CH-8057 Zürich (Switzerland)
We consider QCD radiative corrections to the production of colorless high-mass systems in hadron collisions. The logarithmically-enhanced contributions at small transverse momentum are treated to all perturbative orders by a universal resummation formula that depends on a single process-dependent hard factor. We show that the hard factor is directly related to the all-order virtual amplitude of the corresponding partonic process. The direct relation is universal (process-independent), and it is expressed by an all-order factorization formula that we explicitly evaluate up to the next-to-next-to-leading order (NNLO) in QCD perturbation theory. Once the NNLO scattering amplitude is available, the corresponding hard factor is directly determined: it controls NNLO contributions in resummed calculations at full next-to-next-to-leading logarithmic accuracy, and it can be used in applications of the q{sub T} subtraction formalism to perform fully-exclusive perturbative calculations up to NNLO. The universality structure of the hard factor and its explicit NNLO form are also extended to the related formalism of threshold resummation.
Energy Technology Data Exchange (ETDEWEB)
We present results from a calculation of the transition temperature in QCD with two light (up, down) and one heavier (strange) quark mass as well as for QCD with three degenerate quark masses. Furthermore, we discuss first results from an ongoing calculation of the QCD equation of state with almost realistic light and strange quark masses.
Aspects of confinement in QCD from lattice simulations
Energy Technology Data Exchange (ETDEWEB)
Spielmann, Daniel
We study confinement in quantum chromodynamics via numerical simulations in the framework of lattice gauge theory. In Landau gauge, the mechanism of confinement is related to the infrared behavior of the ghost and gluon propagators via the Gribov-Zwanziger and Kugo- Ojima scenarios. These scenarios entail a scaling behavior. Functional methods in the continuum allow both for this behavior and for decoupling solutions, while lattice simulations in three and four dimensions yield only the latter. A possible explanation for this mismatch is based on limitations of standard lattice gauge fixing methods. Hence, we investigate a number of alternative gauge fixing algorithms in pure SU(2) gauge theory in two, three and four dimensions. We find that stochastic quantization yields an infrared behavior of the propagators in agreement with the results of standard procedures, even though the Faddeev-Popov operator spectrum indicates some different properties. In the strong-coupling limit, our results challenge the standard picture. In particular, we find in a non-perturbative completion of Landau gauge an enormous effect of the Gribov ambiguity. It entails that no subset of infrared solutions can be excluded yet. Moreover, we study the gluon propagator with free boundary conditions. On large lattices, the results mostly show the standard behavior. We also examine non-periodic gauge transformations. Furthermore, we analyze two topics related to the phase diagram of QCD. First, we explore the sign problem for fermions on the lattice by simulating the three-dimensional Thirring model with a complex Langevin equation. The algorithm succeeds in yielding a 'Silver Blaze' behavior of observables, but it does not reliably describe the onset to a phase with non-zero density. Second, we determine properties of the deconfinement phase transition of pure SU(2) gauge theory in 2+1 dimensions, like the critical temperature, by means of the gluon propagator in Landau gauge. (orig.)
Gedanken Worlds without Higgs: QCD-Induced Electroweak Symmetry Breaking
Energy Technology Data Exchange (ETDEWEB)
Quigg, Chris; /Fermilab /Karlsruhe U., TTP; Shrock, Robert; /YITP, Stony Brook
To illuminate how electroweak symmetry breaking shapes the physical world, we investigate toy models in which no Higgs fields or other constructs are introduced to induce spontaneous symmetry breaking. Two models incorporate the standard SU(3){sub c} {circle_times} SU(2){sub L} {circle_times} U(1){sub Y} gauge symmetry and fermion content similar to that of the standard model. The first class--like the standard electroweak theory--contains no bare mass terms, so the spontaneous breaking of chiral symmetry within quantum chromodynamics is the only source of electroweak symmetry breaking. The second class adds bare fermion masses sufficiently small that QCD remains the dominant source of electroweak symmetry breaking and the model can serve as a well-behaved low-energy effective field theory to energies somewhat above the hadronic scale. A third class of models is based on the left-right-symmetric SU(3){sub c} {circle_times} SU(2){sub L} {circle_times} SU(2){sub R} {circle_times} U(1)B?L gauge group. In a fourth class of models, built on SU(4){sub PS} {circle_times} SU(2){sub L} {circle_times} SU(2){sub R} gauge symmetry, lepton number is treated as a fourth color. Many interesting characteristics of the models stem from the fact that the effective strength of the weak interactions is much closer to that of the residual strong interactions than in the real world. The Higgs-free models not only provide informative contrasts to the real world, but also lead us to consider intriguing issues in the application of field theory to the real world.
Next-to-leading order QCD predictions for $A^{0}Z^{0}$ associated production at the CERN Large Hadron Collider
Qiang, Li; Jian, Jun-Liu; Li, Gang-Jin; Yuan, C P; 10.1103/PhysRevD.72.034032
We present the calculations of the complete next-to-leading order (NLO) QCD corrections (including supersymmetric QCD) to the inclusive total cross sections of the associated production processes pp to A /sup 0/Z/sup 0/+X in the minimal supersymmetric standard model at the CERN Large Hadron Collider. Both the dimensional regularization scheme and the dimensional reduction scheme are used to organize the calculations, which yield the same NLO rates. The NLO correction can either enhance or reduce the total cross sections, but it generally efficiently reduces the dependence of the total cross sections on the renormalization/factorization scale. We also examine the uncertainty of the total cross sections due to the parton distribution function uncertainties.
Hardness and excitation energy
Indian Academy of Sciences (India)
It is shown that the first excitation energy can be given by the Kohn-Sham hardness (i.e. the energy difference of the ground-state lowest unoccupied and highest occupied levels) plus an extra term coming from the partial derivative of the ensemble exchange-correlation energy with respect to the weighting factor in the ...
Citron, Z; The ATLAS collaboration
The ATLAS collaboration has measured several hard probe observables in Pb+Pb and p+Pb collisions at the LHC. These measurements include jets which show modification in the hot dense medium of heavy ion collisions as well as color neutral electro-weak bosons. Together, they elucidate the nature of heavy ion collisions.
Indian Academy of Sciences (India)
where H is the hardness, k the coefficient, G the shear modulus, ν the Poisson's ratio, η a function of the radius of an atom (r) and the electron density at the atom interface (n). The formula will not only be used to testify the critical grain size with stable dislocations, but also play an important role in the understanding of ...