论文标题
研究细胞核大小在相对论重离子碰撞中的影响
Studying the impact of the nucleon size in relativistic heavy-ion collisions
论文作者
论文摘要
相对论重离子碰撞模拟的流体动力阶段需要系统的能量密度作为初始条件。在将两个碰撞核转换为这样的能量分布的过程中，必须不可避免地要制作一些有关其组成核的$ \ textit {size} $的规范。核子通常被建模为双二维高斯人，而高斯宽度（核子宽度）是模拟的自由参数。可以通过贝叶斯分析来推断核子宽度的最佳拟合值，在该分析中，该模型面临实验数据。 一些最近的分析获得了核子宽度参数的惊人值，超过50％的质子电荷半径的当前值。这激发了对模拟中此参数扮演的角色的更好理解。 In this work, we perform simulations of Pb-Pb collisions at $\sqrt{s_{\text{NN}}}$ = 2.76 TeV using a state-of-the-art hybrid simulation chain, using three different values of the nucleon width inside the initial condition generator T$_{\text{R}}$ENTo, and systematically investigate its effects on the initial condition characteristics and可观察到。核定宽度强烈影响偏心量谐波和初始条件下的梯度。 $ \ langle p_ {t} \ rangle $在模拟中使用$ W $ = 0.5 fm的粒子比实验数据大得多。我们将其与在初始条件下较强梯度的组合结合在一起，并将保形前平衡动力学与流体动力学模拟偶联。我们的发现表明，通过在初始条件下抑制梯度来降低平均横向动量，必须通过最近的贝叶斯分析返回的细胞核宽度的较大值。
The hydrodynamic stage of relativistic heavy-ion collisions simulations requires an energy density profile of the system as an initial condition. In the process of converting the two colliding nuclei into such an energy distribution, some specification about the $\textit{size}$ of their constituent nucleons inevitably has to be made. Nucleons are commonly modeled as bidimensional Gaussians, and the Gaussian width (the nucleon-width) is a free parameter of the simulation. A best-fit value of the nucleon-width can be inferred by Bayesian Analyses, where the model is confronted with experimental data. Some of the most recent analyses have obtained surprisingly large values for the nucleon width parameter, exceeding in over 50 % the current value for the proton charged radius. This motivates the development of a better understanding of the role played by this parameter inside the simulation. In this work, we perform simulations of Pb-Pb collisions at $\sqrt{s_{\text{NN}}}$ = 2.76 TeV using a state-of-the-art hybrid simulation chain, using three different values of the nucleon width inside the initial condition generator T$_{\text{R}}$ENTo, and systematically investigate its effects on the initial condition characteristics and observables. The nucleon-width strongly affects the eccentricity harmonics and the gradients in the initial condition. The $\langle p_{T} \rangle$ of particles in the simulation using $w$ = 0.5 fm is much larger than experimental data. We associate this to the combination of stronger gradients in the initial condition and the coupling of a conformal pre-equilibrium dynamics to the hydrodynamic simulation. Our findings suggest that the large values of the nucleon width returned by recent Bayesian Analyses were necessary to lower the mean transverse momentum, by damping the gradients in the initial condition.
