Fourth-order Correlations of Conserved Charges in the QCD Thermodynamics

TL;DR

This paper investigates fourth-order correlations of conserved charges in QCD thermodynamics, revealing their critical behavior near the QCD critical point and proposing their use as probes in heavy ion collision experiments.

Contribution

It provides a detailed analysis of fourth-order correlations at finite temperature and chemical potential, highlighting their divergence at the QCD critical point and potential as experimental probes.

Findings

Fourth-order correlations change rapidly during the chiral crossover.

Correlations diverge at the QCD critical point.

Most correlations are effective probes for the QCD critical point.

Abstract

The fourth-order correlations of conserved charges, such as the baryon number, electric charge, and strangeness, are studied at finite temperature and nonzero baryon chemical potential in an effective model. It is found that the fourth-order correlations change rapidly and have three extrema during the chiral crossover with the increase of the baryon chemical potential. The absolute values of the extrema approach infinity when the thermodynamical system moves toward the QCD critical point and the fourth-order correlations are divergent at the critical point. The contour plots of the fourth-order correlations in the plane of the temperature and baryon chemical potential are given. It is noticed that all the fourth-order correlations of conserved charges, except for $\chi_{13}^{BS}$ and $\chi_{13}^{QS}$, are excellent probes to explore the QCD critical point in heavy ion collision experiments.