为什么$v_4/(v_2)^2$比流体力学预测的要大？
Why is $v_4/(v_2)^2$ larger than predicted by hydrodynamics?
摘要：
在相对论重离子对撞机（RHIC）上测量了金-金碰撞中粒子方位角分布的二次和四次傅里叶谐波$v_2$和$v_4$。比值$v_4/(v_2)^2$明显大于流体动力学预测值。部分热化的影响估计的基础上的运输计算，并示出增加的比例由一个小的量。我们认为，实验上看到的大值的$v_4/(v_2)^2$主要是由于椭圆流波动。然而，偏心率波动的标准模型无法解释中心碰撞中$v_4/(v_2)^2$的大幅度。
英文摘要：
The second and fourth Fourier harmonics of the azimuthal distribution of particles, $v_2$ and $v_4$, have been mesured in Au-Au collisions at the Relativistic Heavy Ion Collider (RHIC). The ratio $v_4/(v_2)^2$ is significantly larger than predicted by hydrodynamics. Effects of partial thermalization are estimated on the basis of a transport calculation, and are shown to increase the ratio by a small amount. We argue that the large value of $v_4/(v_2)^2$ seen experimentally is mostly due to elliptic flow fluctuations. However, the standard model of eccentricity fluctuations is unable to explain the large magnitude of $v_4/(v_2)^2$ in central collisions.
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