Higher order fluctuations and correlations of conserved charges from lattice QCD

TL;DR

This paper uses lattice QCD simulations to compute higher order fluctuations and correlations of conserved charges, providing insights into the behavior of net-baryon number cumulants relevant for heavy-ion collision experiments.

Contribution

It introduces a method to calculate higher order fluctuations at zero chemical potential via derivatives from imaginary chemical potential data, applied to 2+1+1 flavor lattice QCD.

Findings

Ratios of net-baryon number cumulants match experimental data qualitatively.

Higher order fluctuations are successfully derived from lower order ones.

Results support the understanding of conserved charge fluctuations in QCD at finite temperature.

Abstract

We calculate several diagonal and non-diagonal fluctuations of conserved charges in a system of 2+1+1 quark flavors with physical masses, on a lattice with size $48^3\times12$. Higher order fluctuations at $\mu_B=0$ are obtained as derivatives of the lower order ones, simulated at imaginary chemical potential. From these correlations and fluctuations we construct ratios of net-baryon number cumulants as functions of temperature and chemical potential, which satisfy the experimental conditions of strangeness neutrality and proton/baryon ratio. Our results qualitatively explain the behavior of the measured cumulant ratios by the STAR collaboration.