"Table 133" of "Anisotropic flow and flow fluctuations of identified hadrons in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV"
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The first measurements of elliptic flow of $\mathrm{\pi}^{\pm}$, $\mathrm{K}^{\pm}$, $\mathrm{p}+\bar{\mathrm{p}}$, $\mathrm{K_{S}^{0}}$, $\Lambda+\bar{\Lambda}$, $\mathrm{\phi}$, $\mathrm{\Xi^{\mp}}$, and $\mathrm{\Omega^{\mp}}$ using multiparticle cumulants in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV are presented. Results obtained with two- ($v_2\{2\}$) and four-particle cumulants ($v_2\{4\}$) are shown as a function of transverse momentum, $p_{\rm T}$, for various collision centrality intervals. Combining the data for both $v_2\{2\}$ and $v_2\{4\}$ also allows us to report the first measurements of the mean elliptic flow, elliptic flow fluctuations, and relative elliptic flow fluctuations for various hadron species. These observables probe the event-by-event eccentricity fluctuations in the initial state and the contributions from the dynamic evolution of the expanding quark--gluon plasma. The characteristic features observed in previous $p_{\rm T}$-differential anisotropic flow measurements for identified hadrons with two-particle correlations, namely the mass ordering at low $p_{\rm T}$ and the approximate scaling with the number of constituent quarks at intermediate $p_{\rm T}$, are similarly present in the four-particle correlations and the combinations of $v_2\{2\}$ and $v_2\{4\}$. In addition, a particle species dependence of flow fluctuations is observed that could indicate a significant contribution from final state hadronic interactions. The comparison between experimental measurements and CoLBT model calculations, which combine the various physics processes of hydrodynamics, quark coalescence, and jet fragmentation, illustrates their importance over a wide $p_{\rm T}$ range.
本研究首次报道了质心系能量√s_NN=5.02 TeV的铅核-铅核(Pb--Pb)碰撞中,利用多粒子累积量(multiparticle cumulants)测量π^±、K^±、p+$ar{p}$、K_S^0、Λ+$ar{Λ}$、φ、Ψ^∓以及Ω^∓的椭圆流(elliptic flow)的实验结果。研究展示了通过两粒子累积量(v2{2})与四粒子累积量(v2{4})得到的椭圆流结果随横向动量(transverse momentum, p_T)的变化关系,覆盖多个碰撞中心度区间。通过联合分析v2{2}与v2{4}的实验数据,我们还首次报道了不同强子种类(hadron species)的平均椭圆流(mean elliptic flow)、椭圆流涨落(elliptic flow fluctuations)以及相对椭圆流涨落(relative elliptic flow fluctuations)的测量结果。上述观测量可用于探究初始态(initial state)的逐事件偏心率涨落(event-by-event eccentricity fluctuations),以及膨胀夸克胶子等离子体(quark-gluon plasma)的动力学演化贡献。此前利用两粒子关联(two-particle correlations)对已鉴别强子进行p_T微分各向异性流(anisotropic flow)测量时观测到的典型特征——即低p_T区间的质量排序,以及中间p_T区间随组分夸克(constituent quarks)数目的近似标度行为——在四粒子关联(four-particle correlations)以及v2{2}与v2{4}的联合分析中同样存在。此外,本研究观测到椭圆流涨落存在强子种类依赖性,这暗示末态强相互作用(final state hadronic interactions)可能存在显著贡献。将实验测量结果与结合了流体力学(hydrodynamics)、夸克聚合(quark coalescence)与喷注碎裂(jet fragmentation)等多种物理过程的CoLBT模型(CoLBT model)计算结果进行对比,证实了这些物理过程在宽泛p_T区间内的重要性。



