Higher order cumulants of electric charge and strangeness fluctuations on the crossover line

TL;DR

This paper uses lattice QCD to calculate higher order cumulants of electric charge and strangeness fluctuations near the crossover line, providing insights into freeze-out conditions in heavy ion collisions.

Contribution

It introduces NNNLO Taylor expansions for cumulants and compares lattice results with experimental data to constrain freeze-out parameters.

Findings

Ratios of cumulants match experimental measurements on the pseudo-critical line.

Computed strangeness chemical potential ratios agree with experimental freeze-out fits.

Strong constraints on freeze-out parameters are established from cumulant comparisons.

Abstract

We present lattice QCD calculations of higher order cumulants of electric charge distributions for small baryon chemical potentials $\mu_B$ by using up to NNNLO Taylor expansions. Ratios of these cumulants are evaluated on the pseudo-critical line, $T_{pc}(\mu_B)$, of the chiral transition and compared to corresponding measurements in heavy ion collision experiments by the STAR and PHENIX Collaborations. We demonstrate that these comparisons give strong constraints on freeze-out parameters. Furthermore, we use strangeness fluctuation observables to compute the ratio $\mu_S/\mu_B$ on the crossover line and compare it to $\mu_S/\mu_B$ at freeze-out stemming from fits to strange baryon yields measured by the STAR Collaboration.