论文标题
事件活动变量对等异形碰撞中可观察物的比率的影响
Impact of event activity variable on the ratio of observables in isobar collisions
论文作者
论文摘要
$^{96} $ ru+$^{96} $ ru和$^{96} $ zr+$^{96} $ zr碰撞的星星isobar数据例如多重分布，$ p（n _ {\ mathrm {ch}}}）$，以及谐波流量，$ v_n $，偏离统一，作为中心性的函数，$ c $。这些偏差归因于$^{96} $ ru和$^{96} $ zr nuclei之间的形状和径向轮廓的差异。此外，比率$ r _ {\ mathcal {o}}（x）$取决于事件活动变量$ x $的选择，这可以是$ n _ {\ mathrm {ch}}} $或中心性。 We estimate the difference $ΔR$ between these two choices, based on the published $p(N_{\mathrm{ch}})$, as well as those from a multiphase transport (AMPT) model with varied nuclear structure parameters: nuclear radius ($R_0$), surface diffuseness ($a_0$), quadrupole deformation ($β_2$), and octupole deformation （$β_3$）。与$ r_ {v_n}（c）$，$ r_ {v_n}（n _ {\ mathrm {ch}}}）$相反，几乎与分析方法无关，这表明非流量效应由$ n _ {\ sathrm {ch ch}} $ c $更好地控制。对于$ x = n _ {\ mathrm {ch}} $而不是$ x = c $，对手性磁效应（CME）敏感的观测值的比率也更接近Unity。根据AMPT结果，$ΔR$的主要参数为$ A_0 $，而$ R_0 $和$β_N$仅在中央碰撞中很重要。已发布的$ p（n _ {\ mathrm {ch}}）$也用于估计$Δr_ {{\ left \ langle p _ {{t} {t} {t}} \ right \ rangle _ p _ {\ mathrm {t}}} \ right \ rangle} -1 $。
The STAR isobar data of $^{96}$Ru+$^{96}$Ru and $^{96}$Zr+$^{96}$Zr collisions at $\sqrt{s_{\mathrm{NN}}}= 200$ GeV show that ratios of observables ($R_{\mathcal{O}}$) such as the multiplicity distribution, $p(N_{\mathrm{ch}})$, and the harmonic flow, $v_n$, deviate from unity, when presented as a function of centrality, $c$. These deviations have been attributed to the differences in the shape and radial profiles between $^{96}$Ru and $^{96}$Zr nuclei. In addition, the ratios $R_{\mathcal{O}}(x)$ depend on the choice of the event activity variable $x$, which could be either $N_{\mathrm{ch}}$ or centrality. We estimate the difference $ΔR$ between these two choices, based on the published $p(N_{\mathrm{ch}})$, as well as those from a multiphase transport (AMPT) model with varied nuclear structure parameters: nuclear radius ($R_0$), surface diffuseness ($a_0$), quadrupole deformation ($β_2$), and octupole deformation ($β_3$). In contrary to $R_{v_n}(c)$, $R_{v_n}(N_{\mathrm{ch}})$ is nearly independent of the analysis approaches, suggesting that nonflow effects are better controlled by $N_{\mathrm{ch}}$ than $c$. The ratios of observables sensitive to the chiral magnetic effect (CME) are also much closer to unity for $x=N_{\mathrm{ch}}$ than $x=c$, indicating that the ratios calculated at the same $N_{\mathrm{ch}}$ provide a better baseline for the non-CME background. According to the AMPT results, the dominant parameter for $ΔR$ is $a_0$, while $R_0$ and $β_n$ are only important in central collisions. The published $p(N_{\mathrm{ch}})$ is also used to estimate $ΔR_{\left\langle p_{\mathrm{T}}\right\rangle}$ for mean transverse momentum, which is non-negligible compared with $R_{\left\langle p_{\mathrm{T}}\right\rangle}-1$.
