Measurement of higher cumulants of net-charge multiplicity distributions in Au$+$Au collisions at $\sqrt{s_{_{NN}}}=7.7-200$ GeV

TL;DR

This study measures higher-order cumulants of net-charge distributions in gold-gold collisions across a range of energies to explore the QCD phase diagram and search for critical phenomena, finding no nonmonotonic behavior.

Contribution

It provides the first comprehensive measurement of net-charge cumulant ratios over a wide energy range, comparing results with theoretical models to inform the QCD phase diagram.

Findings

Cumulant ratios are well described by negative binomial distributions.

No nonmonotonic behavior observed in cumulant ratios across energies.

Results enable extraction of freeze-out parameters for QCD studies.

Abstract

We report the measurement of cumulants ($C_n, n=1\ldots4$) of the net-charge distributions measured within pseudorapidity ($|\eta|<0.35$) in Au$+$Au collisions at $\sqrt{s_{_{NN}}}=7.7-200$ GeV with the PHENIX experiment at the Relativistic Heavy Ion Collider. The ratios of cumulants (e.g. $C_1/C_2$, $C_3/C_1$) of the net-charge distributions, which can be related to volume independent susceptibility ratios, are studied as a function of centrality and energy. These quantities are important to understand the quantum-chromodynamics phase diagram and possible existence of a critical end point. The measured values are very well described by expectation from negative binomial distributions. We do not observe any nonmonotonic behavior in the ratios of the cumulants as a function of collision energy. The measured values of $C_1/C_2 = \mu/\sigma^2$ and $C_3/C_1 = S\sigma^3/\mu$ can be directly compared to lattice quantum-chromodynamics calculations and thus allow extraction of both the chemical freeze-out temperature and the baryon chemical potential at each center-of-mass energy.