Cumulants of event-by-event net-strangeness distributions in Au + Au collisions at $\sqrt{s_{\mathit{NN}}}=7.7\text{–}200$ GeV within an UrQMD model

Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in heavy-ion collisions to search for the QCD phase transition and critical point. In this paper, we performed a systematical analysis on the various cumulants and cumulant ratios of event-by-event net-strangeness distributions in Au+Au collisions at $\sqrt{s_{\mathit{NN}}}=7.7$, 11.5, 19.6, 27, 39, 62.4, and 200 GeV from an ultrarelativistic quantum molecular dynamics model. We performed a systematical study on the contributions from various strange baryons and mesons to the net-strangeness fluctuations. The results demonstrate that the cumulants and cumulant ratios of net-strangeness distributions extracted from different strange particles show very different centrality and energy-dependence behavior. By comparing with the net-kaon fluctuations, we found that the strange baryons play an important role in the fluctuations of net strangeness. This study can provide useful baselines to study the QCD phase transition and search for the QCD critical point by using the fluctuations of net strangeness in heavy-ion collisions experiment. It can help us to understand noncritical physics contributions to the fluctuations of net strangeness.

Figure 1

The $dN/d\eta$ distribution of strange and antistrange quark multiplicities in four different cases in 0–5% most central Au+Au collisions at $\sqrt{s_{\mathit{NN}}}=7.7$, 11.5, 19.6, 27, 39, 62.4, and 200 GeV from the UrQMD model.

Figure 2

Energy dependence of yields ratio for the most central (0–5%) Au+Au collisions at midrapidity ($\left|\eta \right|<0.5$) from the UrQMD model.

Figure 3

Various cumulants of net-strangeness multiplicity distributions as a function of $N_{\mathrm{part}}$ at midrapidity region ($\left|\eta \right|<0.5$) for Au+Au collisions at $\sqrt{s_{\mathit{NN}}}=7.7$, 11.5, 19.6, 27, 39, 62.4, and 200 GeV with the UrQMD model.

Figure 4

Pseudorapidity window size dependence of various cumulants of net-strangeness distributions for the most central (0–5%) Au+Au collisions from $\sqrt{s_{\mathit{NN}}}=7.7\text{–}200$ GeV with the UrQMD model.

Figure 5

Energy dependence of various cumulants of net-strangeness multiplicity distributions at midrapidity region ($\left|\eta \right|<0.5$) for most central (0–5%) Au+Au collisions with the UrQMD model.

Figure 6

Centrality dependence of $\kappa {\sigma }^2$ in Au+Au collisions at $\sqrt{s_{\mathit{NN}}}=7.7\text{–}200$ GeV from the UrQMD model.

Figure 7

Centrality dependence of $S\sigma$ in the Au+Au collisions at $\sqrt{s_{\mathit{NN}}}=7.7\text{–}200$ GeV from the UrQMD model.

Figure 8

Energy dependence of cumulant ratios ($\kappa {\sigma }^2,S\sigma$) of net-strangeness multiplicity distribution in the most central (0–5%) Au+Au collisions at midrapidity ($\left|\eta \right|<0.5$) with the UrQMD model.