Thermal model description of p\u2013Pb collisions at sqrt{s_{NN}} = 5.02\xa0TeV

Natasha Sharma,Jean Cleymans,Lokesh Kumar

doi:10.1140/epjc/s10052-018-5767-3

Abstract

The ALICE data on light flavor hadron production obtained in p–Pb collisions at sqrt{s_{NN}} = 5.02 TeV are studied in the thermal model using the canonical approach with exact strangeness conservation. The chemical freeze-out temperature is independent of centrality except for the lowest multiplicity bin, with values close to 160 MeV but consistent with those obtained in Pb–Pb collisions at sqrt{s_{NN}} = 2.76 TeV. The value of the strangeness non-equilibrium factor gamma _s is slowly increasing with multiplicity from 0.9 to 0.96, i.e. it is always very close to full chemical equilibrium.

Highlights

IntroductionOver the last three decades, the hadron resonance gas (thermal model for short) in its grand-canonical (GC) and canonical formulations has been very successful in describing the abundances of light flavored hadron obtained in heavy-ion collisions [1,2,3] up to the highest beam energies
Over the last three decades, the hadron resonance gas in its grand-canonical (GC) and canonical formulations has been very successful in describing the abundances of light flavored hadron obtained in heavy-ion collisions [1,2,3] up to the highest beam energies.The thermal model has a long history going back to papers by Heisenberg [4], Fermi [5] and Hagedorn [6]
The value of the strangeness non-equilibrium factor γs is slowly increasing with multiplicity from 0.9 to 0.96, i.e. it is always very close to full chemical equilibrium

Summary

Introduction

Over the last three decades, the hadron resonance gas (thermal model for short) in its grand-canonical (GC) and canonical formulations has been very successful in describing the abundances of light flavored hadron obtained in heavy-ion collisions [1,2,3] up to the highest beam energies. The model uses a minimal number of parameters, mainly, the chemical freeze-out temperature Tch, the baryon chemical potential μB and the volume V. In the present paper we investigate in detail the particle abundances in p–Pb collisions [7,8,9,10] in the hope that this contributes to the understanding and the status of the model description. Our results show that there is no clear dependence on the centrality, as measured by the values of d Nch/dη, for the chemical freeze-out temperature. This confirms results obtained earlier on the dependence of thermal parameters on the size of the system obtained [13].

The model

Scaling of yields with strange quark content

Fits using the thermal model

Conclusions