Effects of centrality fluctuation and deuteron formation on proton number cumulant in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 3 GeV from JAM model

TL;DR

This study investigates how centrality fluctuations and deuteron formation influence proton number cumulants and correlations in low-energy Au+Au collisions using the JAM model, highlighting challenges in centrality determination and implications for QCD critical point searches.

Contribution

It provides a detailed analysis of cumulants and correlations affected by centrality resolution and deuteron formation at 3 GeV, offering insights for future event classification methods.

Findings

Centrality resolution using charged particles is insufficient at low energies.

Deuteron formation suppresses higher-order cumulants and correlations.

Results serve as a baseline for QCD critical point search at high baryon density.

Abstract

We studied the effects of centrality fluctuation and deuteron formation on the cumulants ($C_n$) and correlation functions ($\kappa_n$) of protons up to sixth order in most central ($b<3$ fm) Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 3 GeV from a microscopic transport model (JAM). The results are presented as a function of rapidity acceptance within transverse momentum $0.4<p_{T}<2 $ GeV/$c$. We compared the results obtained by centrality bin width correction (CBWC) using charged reference particle multiplicity with CBWC done using impact parameter bins. It was found that at low energies the centrality resolution for determining the collision centrality using charged particle multiplicities is not good enough to reduce the initial volume fluctuations effect for higher-order cumulant analysis. New methods need to be developed to classify events with high centrality resolution for heavy-ion collisions at low energies. Finally, we observed that the formation of deuteron will suppress the higher-order cumulants and correlation functions of protons and is found to be similar to the efficiency effect. This work can serve as a noncritical baseline for the QCD critical point search at the high baryon density region.