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Title: Chiral dynamics and peripheral transverse densities

In the partonic (or light-front) description of relativistic systems the electromagnetic form factors are expressed in terms of frame-independent charge and magnetization densities in transverse space. This formulation allows one to identify the chiral components of nucleon structure as the peripheral densities at transverse distances b = O(M{sub {pi}}{sup -1}) and compute them in a parametrically controlled manner. A dispersion relation connects the large-distance behavior of the transverse charge and magnetization densities to the spectral functions of the Dirac and Pauli form factors near the two--pion threshold at timelike t = 4 M{ sub {pi}}{sup 2}, which can be computed in relativistic chiral effective field theory. Using the leading-order approximation we (a) derive the asymptotic behavior (Yukawa tail) of the isovector transverse densities in the "chiral" region b = O(M{sub {pi}}{sup -1}) and the "molecular" region b = O(M{sub N}{sup 2}/M{sub {pi}}{sup 3}); (b) perform the heavy-baryon expansion of the transverse densities; (c) explain the relative magnitude of the peripheral charge and magnetization densities in a simple mechanical picture; (d) include Delta isobar intermediate states and study the peripheral transverse densities in the large-N{ sub c} limit of QCD; (e) quantify the region of transverse distances where the chiral components more » of the densities are numerically dominant; (f) calculate the chiral divergences of the b{sup 2}-weighted moments of the isovector transverse densities (charge and anomalous magnetic radii) in the limit M{sub {pi}} -> 0 and determine their spatial support. Our approach provides a concise formulation of the spatial structure of the nucleon's chiral component and offers new insights into basic properties of the chiral expansion. It relates the information extracted from low-t elastic form factors to the generalized parton distributions probed in peripheral high-energy scattering processes. « less
 [1] ;  [2]
  1. Uppsala University (Sweden)
  2. JLAB, Newport News, VA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
JLAB-THY--13-1763; DOE/OR--23177-2641
Journal ID: ISSN 1029-8479; TRN: US1400167
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of High Energy Physics (Online); Journal Volume: 1401
Springer Berlin
Research Org:
Sponsoring Org:
USDOE Office of Science (SC) (United States)
Country of Publication:
United States
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS Elastic form factors, dispersion relations, chiral effective field theory, 1/Nc expansion, transverse charge and magnetization densities, generalized parton distributions, light–front quantization