Estimation of the shear viscosity at finite net-baryon density from $A+A$ collision data at $\sqrt{s_\mathrm{NN}} = 7.7-200$ GeV
Estimation of the shear viscosity at finite net-baryon density from $A+A$ collision data at $\sqrt{s_\mathrm{NN}} = 7.7-200$ GeV
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DOI：
10.1103/physrevc.91.064901
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发表时间：
2015-02
影响因子：
3.1
通讯作者：
I. Karpenko;P. Huovinen;M. Bleicher;H. Petersen
中科院分区：
文献类型：
--
作者：
I. Karpenko;P. Huovinen;M. Bleicher;H. Petersen
基于相对论流体动力学和输运理论的混合方法多年来已成功应用于超相对论能量重离子碰撞的动力学描述。在这项工作中，引入了一种新的粘性混合模型，该模型采用强子输运方法 UrQMD 来处理反应的早期和晚期非平衡阶段，并引入了用于热稠密夸克-胶子等离子体阶段的 3+1 维粘性流体动力学。该方法包括有限重子数的运动方程，并采用具有有限净重子密度的状态方程，以允许在大范围的光束能量下进行计算。通过与来自 SPS 和 RHIC 的 I 相光束能量扫描的体可观测数据的实验数据进行比较，探索并约束了模型的参数空间。有利的参数值取决于能量，但允许在所研究的整个能量区域中提取流体相中剪切粘度系数与熵密度比 $\eta/s$ 的有效值。 $\eta/s$ 的估计值随着碰撞能量的降低而增加，这可能表明夸克-胶子等离子体的 $\eta/s$ 取决于重化学势 $\mu_B$。
Hybrid approaches based on relativistic hydrodynamics and transport theory have been successfully applied for many years for the dynamical description of heavy ion collisions at ultrarelativistic energies. In this work a new viscous hybrid model employing the hadron transport approach UrQMD for the early and late non-equilibrium stages of the reaction, and 3+1 dimensional viscous hydrodynamics for the hot and dense quark-gluon plasma stage is introduced. This approach includes the equation of motion for finite baryon number, and employs an equation of state with finite net-baryon density to allow for calculations in a large range of beam energies. The parameter space of the model is explored, and constrained by comparison with the experimental data for bulk observables from SPS and the phase I beam energy scan at RHIC. The favored parameter values depend on energy, but allow to extract the effective value of the shear viscosity coefficient over entropy density ratio $\eta/s$ in the fluid phase for the whole energy region under investigation. The estimated value of $\eta/s$ increases with decreasing collision energy, which may indicate that $\eta/s$ of the quark-gluon plasma depends on baryochemical potential $\mu_B$.