Energy Dependence of Moments of Net-Proton, Net-Kaon, and Net-Charge Multiplicity Distributions at STAR

TL;DR

This study measures higher moments of net-proton, net-kaon, and net-charge multiplicity distributions across various energies in heavy-ion collisions to search for signals of the QCD critical point, providing detailed experimental data and model comparisons.

Contribution

It provides the first comprehensive set of efficiency-corrected cumulants and ratios for multiple conserved quantities over a wide energy range in heavy-ion collisions.

Findings

Cumulants and ratios vary with energy and centrality.

Data show deviations from baseline models at certain energies.

Results are consistent with or challenge existing theoretical predictions.

Abstract

One of the main goals of the RHIC Beam Energy Scan (BES) program is to study the QCD phase structure, which includes the search for the QCD critical point, over a wide range of chemical potential. Theoretical calculations predict that fluctuations of conserved quantities, such as baryon number (B), charge (Q), and strangeness (S), are sensitive to the correlation length of the dynamical system. Experimentally, higher moments of multiplicity distributions have been utilized to search for the QCD critical point in heavy-ion collisions. In this paper, we report recent efficiency-corrected cumulants and cumulants ratios of the net- proton, net-kaon, and net-charge multiplicity distributions in Au+Au collisions at 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV collected in the years 2010, 2011, and 2014 with STAR at RHIC. The centrality and energy dependence of the cumulants up to the fourth order, as well as their ratios, are presented. Furthermore, the comparisons with baseline calculations (Poisson) and non-critical-point models (UrQMD) will also be discussed.