Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Phys Rev Lett. 2011 May 13;106(19):192301. doi: 10.1103/PhysRevLett.106.192301. Epub 2011 May 9.
A new robust method to extract the specific shear viscosity (η/s)(QGP) of a quark-gluon plasma (QGP) at temperatures T(c) < T ≲ 2T(c) from the centrality dependence of the eccentricity-scaled elliptic flow v2/ε measured in ultrarelativistic heavy-ion collisions is presented. Coupling viscous fluid dynamics for the QGP with a microscopic transport model for hadronic freeze-out we find for 200 A GeV Au + Au collisions that v2/ε is a universal function of multiplicity density (1/S)(dN(ch)/dy) that depends only on the viscosity but not on the model used for computing the initial fireball eccentricity ε. Comparing with measurements we find 1<4π(η/s)(QGP) < 2.5 where the uncertainty range is dominated by model uncertainties for the values of ε used to normalize the measured v2.
提出了一种新的稳健方法，可从相对论重离子碰撞中测量的各向异性度标度的椭圆流 v2/ε 与中心度的依赖关系中，提取温度 T(c) < T ≲ 2T(c) 下夸克-胶子等离子体(QGP)的具体剪切黏度(η/s)(QGP)。通过将 QGP 的粘性流体动力学与强子冻结的微观输运模型耦合，我们发现对于 200 A GeV Au + Au 碰撞，v2/ε 是多重密度(1/S)(dN(ch)/dy)的通用函数，仅取决于黏度，而与用于计算初始火球各向异性ε的模型无关。与测量结果比较后，我们发现 1<4π(η/s)(QGP) < 2.5，其中不确定性范围主要由用于归一化测量 v2 的ε值的模型不确定性所主导。
