Prediction of Charged Hadron Multiplicity at LHC and CBM Experiments
  A systematic study of charged hadron multiplicities ($n_{ch}$) at various collision energies is very much important in understanding the basic production mechanism of the hadrons in nucleus-nucleus collision experiments. Furthermore, the variations of $n_{ch}$ in nucleus-nucleus collisions with respect to the colliding energy and mass number can provide a potential probe for the formation of quark gluon plasma (QGP) in the laboratory. In this paper, we propose a phenomenological model based on the constituent quark-quark interactions to calculate the average multiplicity ($n_{ch}$) and pseudorapidity density at mid-rapidity ($(dn_{ch}/d\eta)_{\eta=0}$) of charged hadrons at various center-of-mass energies $(\sqrt{s_{NN}})$ for nucleus-nucleus ($A-A$) collisions. We first propose a new parametrization for $n_{ch}^{pp}$ and $(dn_{ch}/d\eta)^{pp}_{\eta=0}$ in $p-p$ interactions based on some initial inputs which fit the experimental data very well. We further extend this parametrization by using simple phenomenological assumptions regarding mean number of participating quarks and mean number of collisions to obtain the $n_{ch}$ and $(dn_{ch}/d\eta)_{\eta=0}$ for $A-A$ collisions and show their dependencies on the mass number of colliding nuclei as well as on $\sqrt{s_{NN}}$. We also compare the results obtained from our model with the results obtained from the modified Glauber model in order to demonstrate the difference between the two formalisms. Finally, we compare the charged hadron multiplicity and pseudorapidity density at mid-rapidity for $A-A$ collisions obtained from our model with the available experimetal data from various heavy-ion collision experiments and give our predictions for $A-A$ collisions at the Large Hadron Collider (LHC) and at Compressed Baryonic Matter (CBM) experiments. 
Ashwini Kumar, P. K. Srivastava, B. K. Singh, and C. P. Singh
hep-ph hep-ex