Baryon Number, Strangeness and Electric Charge Fluctuations in QCD at High Temperature

TL;DR

This study investigates baryon number, strangeness, and electric charge fluctuations in QCD at high temperatures using lattice calculations, comparing results with ideal quark gas and hadron resonance gas models to understand their behavior across the transition temperature.

Contribution

The paper provides lattice QCD results for fluctuations and correlations at high temperature, highlighting their agreement with ideal quark gas models above 1.5 times the transition temperature and deviations near the transition.

Findings

Fluctuations match ideal quark gas predictions above 1.5 T_c.

Hadron resonance gas describes low-temperature features well.

Higher order cumulants deviate near the transition temperature.

Abstract

We analyze baryon number, strangeness and electric charge fluctuations as well as their correlations in QCD at high temperature. We present results obtained from lattice calculations performed with an improved staggered fermion action (p4-action) at two values of the lattice cut-off with almost physical up and down quark masses and a physical value for the strange quark mass. We compare these results, with an ideal quark gas at high temperature and a hadron resonance gas model at low temperature. We find that fluctuations and correlations are well described by the former already for temperatures about 1.5 times the transition temperature. At low temperature qualitative features of the lattice results are quite well described by a hadron resonance gas model. Higher order cumulants, which become increasingly sensitive to the light pions, however show deviations from a resonance gas in the vicinity of the transition temperature.