UrQMD Simulations of Higher-order Cumulants in Au+Au Collisions at High Baryon Density

TL;DR

This study uses UrQMD simulations to analyze higher-order cumulants of proton multiplicity distributions in Au+Au collisions at high baryon density, providing a baseline for critical point searches in heavy-ion collision experiments.

Contribution

It offers a systematic analysis of proton cumulants up to fourth order across various energies, centralities, and rapidity widths, including effects of volume fluctuations, serving as a non-critical baseline for experimental searches.

Findings

Cumulants depend on beam energy, centrality, and rapidity width.

Initial volume fluctuations influence cumulant measurements.

Results aid in interpreting experimental data from RHIC BES and future FAIR CBM experiments.

Abstract

High moments of conserved quantities such as net-baryon, net-electric charge, and net-strangeness in heavy-ion collisions are sensitive to fluctuations caused by the QCD critical point (CP). The event-by-event analysis of high moments of the conserved charges has been widely used in experiments to search for the CP, especially in the RHIC-STAR experiment. In order to establish a {\it dynamical non-critical base line}, especially at the high baryon density region, we have performed a systematic analysis of the proton multiplicity distributions from Au+Au collisions at 3 $\leq$ $\sqrt{s_{NN}}$ $\leq$ 9.2 GeV collisions. The results on beam energy, centrality and rapidity width dependence of proton (factorial) cumulants, up to the $4^{th}$ order, are extracted from the calculations of the hadronic transport model UrQMD. In addition, the effects of initial volume fluctuation is also discussed. These results will be important when we do physics analysis the RHIC beam energy scan (BES) data, especially for the fixed-target data and experimental data from future CBM experiment at FAIR.