"Figure 7.1" of "Collision Energy Dependence of Moments of Net-Kaon Multiplicity Distributions at RHIC"

Fluctuations of conserved quantities such as baryon number, charge, and strangeness are sensitive to the correlation length of the hot and dense matter created in relativistic heavy-ion collisions and can be used to search for the QCD critical point. We report the first measurements of the moments of net-kaon multiplicity distributions in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The collision centrality and energy dependence of the mean ($M$), variance ($\sigma^2$), skewness ($S$), and kurtosis ($\kappa$) for net-kaon multiplicity distributions as well as the ratio $M/\sigma^2$ and the products $S\sigma$ and $\kappa\sigma^2$ are presented. Comparisons are made with Poisson and negative binomial baseline calculations as well as with UrQMD, a transport model (UrQMD) that does not include effects from the QCD critical point. Within current uncertainties, the net-kaon cumulant ratios appear to be monotonic as a function of collision energy.

重子数、电荷与奇异数等守恒量的涨落，对相对论重离子碰撞中产生的热密物质的关联长度具有极高敏感性，可用于搜寻量子色动力学（Quantum Chromodynamics，QCD）临界点。本研究首次测量了质心系能量√s_NN分别为7.7、11.5、14.5、19.6、27、39、62.4与200 GeV的金核-金核（Au+Au）碰撞中净K介子多重数分布的各阶矩。本文给出了净K介子多重数分布的均值（M）、方差（σ²）、偏度（S）与峰度（κ），以及比值M/σ²和乘积Sσ、κσ²随碰撞中心度与碰撞能量的依赖关系。我们将上述结果与泊松分布、负二项分布的基准计算结果，以及不包含QCD临界点效应的超相对论量子分子动力学（UrQMD）输运模型的预言进行了对比。在当前的实验不确定性范围内，净K介子的累积量比值随碰撞能量的变化呈现单调依赖关系。