标题： 通过重离子碰撞中逐事件介子不对称性探测中子皮 显示英文标题

标题： Probing Neutron Skin through Event-by-Event Pion Asymmetry in Heavy-ion collisions

摘要： 在本工作中，我们提出了一种新方法，通过分析事件逐个的$\pi^{-}$和$\pi^{+}$产率差异来探测金（Au）的中子皮厚度。这是通过 SMASH 对 $\sqrt{s_{\rm NN}}=3$ GeV 下的超外围 Au+Au 碰撞进行模拟实现的。我们的结果表明，$\Delta n_{\pi} = n_{\pi^{-}} - n_{\pi^{+}}$的平均值以及$(\pi^{-}+\pi^{+})$和$(\pi^{-}-\pi^{+})$之间的皮尔逊相关性和互信息均与中子皮厚度成线性关系。此外，事件逐个分布中两个不同$\Delta n_{\pi}$值之间连线的斜率也表现出与中子皮厚度的线性依赖关系。 最敏感的$\Delta n_{\pi}$对被确定为$(-1, 1)$,$(-1, 2)$,$(0, 1)$, 和$(0, 2)$。 这些发现建立了一种新的方法来确定中子皮厚度。 最后，通过在相同初始条件下比较SMASH和UrQMD模拟，我们观察到个体斜率值取决于具体的碰撞模型。 然而，通过从实验事件中多个$\Delta n_{\pi}$对中提取斜率并推断相应的中子皮厚度，可以评估哪种模型更符合真实的物理值。 显示英文摘要

摘要： In this work, we propose a novel approach for probing the neutron skin thickness of gold (Au) by analyzing the event-by-event distribution of $\pi^{-}$ and $\pi^{+}$ yield differences. This is achieved through SMASH simulations of ultra-peripheral Au+Au collisions at $\sqrt{s_{\rm NN}}=3$ GeV. Our results demonstrate that the mean value of $\Delta n_{\pi} = n_{\pi^{-}} - n_{\pi^{+}}$, along with the Pearson correlation and mutual information between $(\pi^{-}+\pi^{+})$ and $(\pi^{-}-\pi^{+})$, all scale linearly with the neutron skin thickness. Moreover, the slope of the line connecting two distinct $\Delta n_{\pi}$ values in the event-by-event distribution also exhibits a linear dependence on the neutron skin thickness. The most sensitive $\Delta n_{\pi}$ pairs are identified as $(-1, 1)$, $(-1, 2)$, $(0, 1)$, and $(0, 2)$. These findings establish a new pathway for determining the neutron skin thickness. Finally, by comparing SMASH and UrQMD simulations under identical initial conditions, we observe that individual slope values depend on the specific collision model. However, by extracting slopes from multiple $\Delta n_{\pi}$ pairs in experimental event-by-event data and inferring the corresponding neutron skin thickness, one can assess which model better aligns with the true physical value.