p-Pb collisions at 5.02 TeV in the Parton-Hadron-String-Dynamics transport approach

Abstract

The Parton-Hadron-String-Dynamics (PHSD) transport model is employed for p-Pb collisions at $\sqrt{s_{NN}}=$ 5.02 TeV and compared to recent experimental data from the LHC as well as to alternative models. We focus on the question of initial state dynamics, i.e. if the initial state might be approximated by a superposition of independent nucleon-nucleon collisions or should be considered as a coherent gluon field as predicted within the color glass condensate (CGC) framework. We find that the PHSD approach provides correlations between the charged particle multiplicity at midrapidity and the number of participant nucleons close to results from the CGC and differs substantially from results calculated with independent Glauber initial conditions. However, a sizeable difference is found between the PHSD approach and CGC models with respect to the rapidity dependence of the average transverse momentum. Accordingly, related measurements at LHC should allow to prove or disprove the presence of coherent colour fields in the initial phase of the collisions.