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arXiv 1502.01978nucl-thhep-ph
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用$\sqrt{s_\mathrm{NN}} = 7.7-200$ GeV的A+A碰撞数据估算有限净重子密度下的剪切粘滞系数

Estimation of the shear viscosity at finite net-baryon density from A+A collision data at $\sqrt{s_\mathrm{NN}} = 7.7-200$ GeV

Iu. A. Karpenko, P. Huovinen, H. Petersen, M. Bleicher

备注：
minor changes in the text, results for constant eta*T/w added. Version accepted for publication in Phys. Rev. C
发表信息：
Phys. Rev. C 91, 064901 (2015)
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摘要：

基于相对论流体力学和输运理论的混合方法已经成功地应用于超相对论能量下重离子碰撞的动力学描述多年。本文采用强子输运方法UrQMD对反应的早期和晚期非平衡阶段进行了计算，采用3+1维粘性流体动力学方法对热密的夸克-胶子等离子体阶段进行了计算。这种方法包括有限重子数的运动方程，并采用有限净重子密度的状态方程，以允许在大范围的束能量的计算。探索的参数空间的模型，并约束与SPS和RHIC的第一阶段束能量扫描的体观测量的实验数据进行比较。有利的参数值取决于能量，但允许提取的有效值的剪切粘度系数在熵密度比$η/s$在流体相中的整个能量区域的调查。$η/s$的估计值随碰撞能量的减小而增大，这可能表明夸克-胶子等离子体的$η/s$依赖于重化势$μ_B$ .

英文摘要：

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 $η/s$ in the fluid phase for the whole energy region under investigation. The estimated value of $η/s$ increases with decreasing collision energy, which may indicate that $η/s$ of the quark-gluon plasma depends on baryochemical potential $μ_B$.

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