Mass hierarchy in identified particle distributions in proton-lead collisions

TL;DR

This paper investigates how particle mass influences transverse momentum and flow coefficients in proton-lead collisions, testing collective behavior predictions against initial gluon dynamics to understand the underlying physics.

Contribution

It provides an analysis of mass-dependent observables in p-Pb collisions to distinguish between collective flow and initial gluon dynamics mechanisms.

Findings

Mass ordering observed in transverse momentum and flow coefficients.

Smaller differential elliptic flow for protons than pions at low p_T.

Results support the presence of collective behavior in p-Pb 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.