arXiv 2108.079432021-08-30nucl-thhep-phnucl-ex

高能核碰撞中核心和日冕成分之间的相互作用

Interplay between core and corona components in high-energy nuclear collisions

Yuuka Kanakubo, Yasuki Tachibana, Tetsufumi Hirano

备注：: 25 pages, 9 figures (bug in viewing PDF file is fixed)
DOI：: 10.1103/PhysRevC.105.024905

摘要：

我们建立了更新的动力学核心-日冕初始化框架（DCCI 2），作为从小到大碰撞系统和从低到高横动量（$p_T$）区域的统一描述。使用DCCI 2，我们研究局部平衡和非平衡系统之间的相互作用的影响，换句话说，在高能核碰撞的核心和电晕组件。给出了实验上的多重数分布和$Ω$重子与带电π介子的产额比作为输入，我们提取了$\sqrt{s}=7$ TeV的p+p碰撞和$\sqrt{s_{NN}}=2.76$ TeV的Pb+Pb碰撞中的核和日冕分量.我们发现核心的贡献超过电晕的贡献，增加以上$\langle dN_{\mathrm{ch}}/dη\rangle_{|η|<0.5} \sim 18$的多重性，无论碰撞系统或能量。我们还看到，在p+p碰撞中，核心贡献仅在0.0-0.95\%的多重级中超过日冕贡献。值得注意的是，即使在最小偏压Pb+Pb碰撞中，$\sim20$低于$p_T\sim 1$ GeV时电晕贡献也有小的增强。我们发现，在低$p_T$时的日冕贡献给出了在$N_{\mathrm{ch}}\lesssim 370$时对$38$的$\sim 15$ $\%$修正.这在传统的流体动力学分析中提出了一个问题，在传统的流体动力学分析中，低$p_T$软强子仅来自核心成分。最后，我们仔细研究字符串碎片和纵向膨胀的横向能量每单位快度，这是至关重要的初始条件的流体动力学事件发生器的基础上串模型的作用。

英文摘要：

We establish the updated version of dynamical core--corona initialization framework (DCCI2) as a unified description from small to large colliding systems and from low to high transverse momentum ($p_T$) regions. Using DCCI2, we investigate effects of interplay between locally equilibrated and non-equilibrated systems, in other words, core and corona components in high-energy nuclear collisions. Given experimental multiplicity distributions and yield ratios of $Ω$ baryons to charged pions as inputs, we extract the fraction of core and corona components in p+p collisions at $\sqrt{s}=7$ TeV and Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. We find core contribution overtakes corona contribution as increasing multiplicity above $\langle dN_{\mathrm{ch}}/dη\rangle_{|η|<0.5} \sim 18$ regardless of the collision system or energy. We also see that the core contribution exceeds the corona contribution only in 0.0-0.95\% multiplicity class in p+p collisions. Notably, there is a small enhancement of corona contribution with $\sim20$\% below $p_T\sim 1$ GeV even in minimum bias Pb+Pb collisions. We find that the corona contribution at low $p_T$ gives $\sim 15$-$38$ $\%$ correction on $v_2\{2\}$ at $N_{\mathrm{ch}}\lesssim 370$. This raises a problem in conventional hydrodynamic analyses in which low $p_T$ soft hadrons originate solely from core components. We finally scrutinize the roles of string fragmentation and the longitudinal expansion in the transverse energy per unit rapidity, which is crucial in initial conditions for hydrodynamics from event generators based on string models.

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