Mass hierarchy in identified particle distributions in proton-lead collisions

Abstract

We study the mass dependence for identified-particle average transverse momentum and harmonic flow coefficients in proton-lead (p-Pb) collisions, recently measured at the LHC. The collective mechanism in the p-Pb system predicts a specific mass ordering in these observables: the growth of the average transverse momentum with the particle mass and a mass splitting of the elliptic flow coefficient, i.e., smaller differential elliptic flow of protons than pions for p_T<2 GeV. This provides an opportunity to distinguish between the collective scenario and the mechanism based on the initial gluon dynamics in the evolution of the p-Pb system.