"figure 20 Hydro 3 GeV -0.5

Collision energy dependence of the cumulant ratios: $C_2/C_1=\sigma/M$, $C_3/C_2=S\sigma$, and $C_4/C_2=\kappa\sigma^2$, for protons (open squares) and net protons (red circles) from top 0–5% (top panels) and 50–60% (bottom panels) Au+Au collisions at RHIC. The points for protons are shifted horizontally for clarity. The new result for protons from $\sqrt{s_{\rm NN}}$ = 3 GeV Au+Au collisions is shown as a filled square. UrQMD results with $|y|<0.5$ for protons are shown as gold bands while those for net protons are shown as green dashed lines or green bands. At 3GeV, the model results for protons (−0.5) are shown as blue crosses. UrQMD results of proton and net-proton $C_4/C_2$, see right panels, are almost totally overlapped. The open cross is the result of the model with a fixed impact parameter $b < 3$ fm. The hydrodynamic calculations, for 5% central Au+Au collisions, for protons from $|y|<0.5$ are shown as dashed red linea and the result of the 3 GeV protons from $−0.5

质子与净质子的累积量比值随碰撞能量的依赖关系：$C_2/C_1=sigma/M$、$C_3/C_2=Ssigma$ 以及 $C_4/C_2=kappasigma^2$，数据来自相对论重离子对撞机（Relativistic Heavy Ion Collider, RHIC）上的金核-金核（Au+Au）碰撞，分别选取0–5%最高中心度（上图）与50–60%中心度（下图）两类碰撞事例。为清晰起见，质子数据点沿水平方向做了偏移。来自核子-核子质心系能量 $sqrt{s_{
m NN}}=3 ext{GeV}$ 的金核-金核碰撞中质子的新结果以实心方块呈现。针对快度绝对值 $|y|<0.5$ 的质子，超相对论量子分子动力学（Ultrarelativistic Quantum Molecular Dynamics, UrQMD）模型的计算结果以金色误差带展示；对应净质子的结果则以绿色虚线或绿色误差带展示。在 $sqrt{s_{
m NN}}=3 ext{GeV}$ 能区，快度范围 $|y|<0.5$ 的质子模型结果以蓝色叉点呈现。右侧面板展示了质子与净质子的 $C_4/C_2$ 比值的UrQMD计算结果，二者几乎完全重合。空心叉点代表碰撞参数固定为 $b<3 ext{fm}$ 的模型计算结果。针对5%中心度金核-金核碰撞、快度 $|y|<0.5$ 的质子的流体力学计算结果以红色虚线展示；而 $sqrt{s_{
m NN}}=3 ext{GeV}$ 下3 GeV质子的结果