Centrality selection effect on higher-order cumulants of net-proton multiplicity distributions in relativistic heavy-ion collisions

TL;DR

This study investigates how different methods of selecting collision centrality affect the higher-order cumulants of net-proton multiplicity distributions in heavy-ion collisions, revealing impacts of autocorrelation and spectator protons on fluctuation measurements.

Contribution

It provides a systematic analysis of centrality selection effects on cumulants using the UrQMD model, highlighting optimal methods for fluctuation studies in heavy-ion collisions.

Findings

Autocorrelation effects are minimal with certain centrality definitions.

Spectator protons cause poor centrality resolution at forward rapidity at low energies.

Results serve as a baseline for future fluctuation analyses.

Abstract

We studied the centrality selection effect on cumulants (up to fourth order) and the cumulants ratios of net-proton multiplicity distributions in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 7.7, 19.6 and 200 GeV from UrQMD model. The net-proton cumulants are calculated with collision centralities by using charged particle multiplicity from different pesudorapidity ($\eta$) region. By comparing the results from various collision centralities, we found that the autocorrelation effects are not significant in the results with collision centralities "refmult-3" and "refmult-2", which are using mid-rapidity charged particles but excluding (anti-)protons and analysis region, respectively. Furthermore, due to the contributions of spectator protons, we observed poor centrality resolution when using charged particles at forward $\eta$ region at low energies. This work can serve as a baseline for centrality selection of future fluctuations analysis in relativistic heavy-ion collisions.