改进AMPT模型下$p^{\u2191}$+Au碰撞手征电荷分离的逐事件分析
Event-by-event analysis of chiral charge separation in $p^{\uparrow}+$Au collisions within an improved AMPT model
浏览论文内容
中文总结 AI 辅助
采用改进弦熔化AMPT模型，研究200 GeV $p^{\u2191}$+Au碰撞的逐事件手征磁效应诱导电荷分离，证实$\u0394\u03b3_{\text{IV}}-\u0394\u03b3_{\text{II}}$为无明显本底的CME可观测物理量。
中文摘要 AI 辅助
我们采用改进的弦熔化AMPT模型，对质心系能量$\u221as_{NN}$=200 GeV的$p^{\u2191}$+Au碰撞中由手征磁效应（CME）诱导的电荷分离进行逐事件研究。该模型引入了依赖碰撞参数的形成时间延迟，将峰值Bjorken能量密度从约2 GeV/fm³降至约0.3 GeV/fm³，同时重现了PHENIX合作组在$p$+Au碰撞中测量到的椭圆流$v_2(p_T)$。逐事件CME源的夸克动量交换分数与$|\boldsymbol{B}|_{\text{event}}/|\boldsymbol{B}|_{\text{max}}$成正比，上限为Au+Au碰撞中的7%，它将场几何直接传递给可观测物理量。我们发现初态关联器呈现清晰的与$B^2$相关的方案层级；部分子级联保留约80-90%的信号，而夸克 coalescence（并合）和ART强子再散射耗散了大部分信号，最终仅保留约10-30%；$\u03b3_{OS}/\u03b3_{SS}$的分裂仍可观测。这些结果支持使用方案间差值$\u0394\u03b3_{\text{IV}}-\u0394\u03b3_{\text{II}}$作为无明显本底的CME可观测物理量，该方法是我们前期工作中提出的。
英文摘要
We study the charge separation induced by chiral magnetic effect (CME) in $p^{\uparrow}$+Au collisions at $\sqrt{s_{NN}}=200$ GeV event-by-event with an improved string-melting AMPT model. In this model, an impact-parameter-dependent formation-time delay is introduced to reduce the peak Bjorken energy density from $\sim$2 to $\sim$0.3 GeV/fm$^3$ and reproduces the illiptic flow $v_2(p_T)$ measured by PHENIX in $p+$Au simultaneously. The event-by-event CME source, whose quark momentum-exchange fraction scales with $|\mathbf{B}|_{\mathrm{event}}/|\mathbf{B}|_{\mathrm{max}}$ and is capped at the 7\% value from Au+Au, transmits the field geometry directly to the observable. We find that the initial correlator shows a clear scheme hierarchy tracking $B^2$. The parton cascade preserves $\sim$80--90\% of the signal, while coalescence and ART hadronic rescattering dissipate the bulk, leaving $\sim$10--30\% in the final state. The $γ_{OS}/γ_{SS}$ splitting remains visible. These results support the use of the inter-scheme difference $Δγ_{\mathrm{IV}}-Δγ_{\mathrm{II}}$ as an essentially background-free CME observable as we proposed in previous work.
