Thermal-model-based characterization of heavy-ion-collision systems at chemical freeze-out

Jamie M Karthein,Paolo Alba,Valentina Mantovani-Sarti,Israel Portillo-Vazquez,Claudia Ratti,Volker Koch,Volodymyr Vovchenko,Paolo Parotto,Jacquelyn Noronha-Hostler,G David,P Garg,Z Xu,T Ullrich,I.-K Yoo,A Kalweit,S Mukherjee

doi:10.1051/epjconf/202225911010

Abstract

We investigate the chemical freeze-out in heavy-ion collisions (HICs) and the impact of the hadronic spectrum on thermal model analyses [1, 2]. Detailed knowledge of the hadronic spectrum is still an open question, which has phenomenological consequences on the study of HICs. By varying the number of resonances included in Hadron Resonance Gas (HRG) Model calculations, we can shed light on which particles may be produced. Furthermore, we study the influence of the number of states on the so-called two flavor freezeout scenario, in which strange and light particles can freeze-out separately. We consider results for the chemical freeze-out parameters obtained from thermal model fits and from calculating net-particle fluctuations. We will show the effect of using one global temperature to fit all particles and alternatively, allowing particles with and without strange quarks to freeze-out separately.

Highlights

Ultra-relativistic heavy-ion collisions provide an opportunity to study the transition from ordinary hadronic matter to the deconfined Quark-Gluon Plasma
5.02 GeV data for particle yields in 0 − 10% collisions, in comparison to Hadron Resonance Gas (HRG) model calculations with different resonance lists; deviations in units of experimental errors σ are shown below each panel
This study of the chemical freeze-out stage in heavy-ion collisions is performed within the Hadron Resonance Gas (HRG) model framework

Summary

Introduction

Calculations of the fundamental theory with Lattice Quantum Chromodynamics have shown there exists a crossover transition at low baryon chemical potential around T ∼ 156 MeV [3] During this transition, the system traverses through chemical and kinetic freeze-out stages. One can determine the freeze-out parameters by utilizing net-charge fluctuations [6] This method allows for the determination of freeze-out parameters for different particle species separately, for example for light particles and kaons [2, 6]. In these proceedings, freeze-out parameters are analyzed both via thermal fits and net-particle fluctuations. 5.02 GeV data for particle yields in 0 − 10% collisions, in comparison to HRG model calculations with different resonance lists; deviations in units of experimental errors σ are shown below each panel

HRG Model

Thermal model fits

Net-particle fluctuations

Conclusions