AI 中文总结
该研究利用fRG和SMASH模型，探究了√s_NN为3.0至7.7 GeV时强子再散射对净质子累积量的影响，发现其会显著削弱C₄/C₂，是提取QCD临界点信号需考虑的重要背景效应。
AI 中文摘要
重离子碰撞的束流能量扫描区域中的净质子累积量被广泛用于探测与量子色动力学（QCD）推测的临界端点相关的临界涨落。然而，现有多数研究集中于初态或相变贡献，而强子再散射对这些观测量的影响尚未完全量化。为填补这一空白，我们利用最大熵原理从函数重整化群（fRG）累积量构建逐事件的质子与反质子分布，并在简化的球对称演化设置中通过强子输运模型SMASH传播生成的粒子。我们系统研究了强子级联在质心系能量√s_NN=3.0、3.9、4.9、7.2和7.7 GeV时如何修正净质子累积量。在严格保证净重子数守恒的正则系综框架下，高阶累积量信号——尤其是√s_NN=4.9 GeV时的比值C₄/C₂——在级联早期被大幅削弱，C₄/C₂的抑制幅度约达20%；源自fRG输入的非单调能量依赖关系在强子演化中得以保留，但其大小被显著改变。这些结果表明，强子再散射是不可忽略的背景效应，从实验数据中提取QCD临界点信号时必须将其考虑在内。
英文摘要
Net-proton cumulants in the Beam Energy Scan region of heavy-ion collisions are widely used to probe critical fluctuations associated with the conjectured critical endpoint of Quantum Chromodynamics (QCD). Most existing studies, however, concentrate on the initial-state or phase-transition contributions, while the impact of hadronic rescattering on these observables has not been fully quantified. To address this gap, we construct event-by-event proton and antiproton distributions from functional renormalization group (fRG) cumulants using the maximum entropy principle, and propagate the resulting particles through the hadronic transport model SMASH in a simplified spherical evolution setup. We systematically investigate how the hadronic cascade modifies net-proton cumulants at collision energies $\sqrt{s_{NN}}=3.0$, 3.9, 4.9, 7.2, and 7.7~GeV. In the canonical-ensemble framework, which enforces exact net-baryon number conservation, the higher-order cumulant signal---in particular the ratio $C_4/C_2$ at $\sqrt{s_{NN}}=4.9$~GeV---is strongly reduced during the early stage of the cascade; the suppression of $C_4/C_2$ reaches approximately $20\%$. The non-monotonic energy dependence inherited from the fRG input survives the hadronic evolution, but its magnitude is substantially modified. These results demonstrate that hadronic rescattering provides a non-negligible background effect that must be accounted for when extracting QCD critical-point signals from experimental data.
