Fluctuating temperature and baryon chemical potential in heavy-ion collisions and the position of the critical end point in the effective QCD phase diagram

Alejandro Ayala,Víctor Knapp-Pérez,Saul Hernández-Ortiz,L A Hernández,R Zamora

doi:10.1103/physrevd.101.074023

Abstract

We use the linear sigma model with quarks to locate the critical end point in the effective QCD phase diagram accounting for fluctuations in temperature and quark chemical potential. For this purpose, we use the non-equilibrium formalism provided by the superstatistics framework. We compute the effective potential in the high- and low-temperature approximations up to sixth order and include the contribution of ring diagrams to account for plasma screening effects. We fix the model parameters from relations between the thermal sigma and pion masses imposing a first order phase transition at zero temperature and a finite critical value for the baryon chemical potential that we take of order of the nucleon mass. We find that the CEP displacement due to fluctuations in temperature and/or quark chemical potential is almost negligible.

Highlights

The study of the transition describing the phase change from nuclear to quark-gluon matter with an increasing temperature (T) and baryon chemical potential constitutes one of the most active fields of research of modern high-energy nuclear physics
We compute the effective potential in the high- and low-temperature approximations up to sixth order and include the contribution of ring diagrams to account for plasma screening effects
We have used the linear sigma model with quarks (LSMq) to locate the critical end point (CEP) in the effective QCD phase diagram taking into account fluctuations in the temperature and the quark chemical potential

Summary

INTRODUCTION

The study of the transition describing the phase change from nuclear to quark-gluon matter with an increasing temperature (T) and baryon chemical potential (μB) constitutes one of the most active fields of research of modern high-energy nuclear physics. If overall thermalization is to be achieved, it seems natural to assume that these regions form subsystems from where thermalization spreads later over the entire reaction volume In this scenario, the temperature and chemical potential between subsystems may not be the same. We reserve for the Appendixes the explicit computation of the vacuum stability conditions and the temperature and baryon chemical potential dependence of the effective coupling constants

SUPERSTATISTICS

DETERMINATION OF THE FREE PARAMETERS

QCD PHASE DIAGRAM

SUMMARY AND CONCLUSIONS