Quark-gluon plasma formation time and direct photons from heavy ion collisions
Quark-gluon plasma formation time and direct photons from heavy ion collisions
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DOI：
10.1103/physrevc.89.034906
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发表时间：
2012-12
影响因子：
3.1
通讯作者：
Fuming Liu;Sheng-Xu Liu
中科院分区：
文献类型：
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作者：
Fuming Liu;Sheng-Xu Liu
本文研究了大型强子对撞机（LHC）上2.76TeV能量的Pb+Pb碰撞和相对论重离子对撞机（RHIC）上200 GeV能量的Au+Au碰撞的直接光子数据所携带的信息，即横动量谱和椭圆流v2，在强子数据约束的（3+1）维理想流体动力学模型框架下，我们发现，这些直接光子数据可以作为一个有用的时钟在重离子碰撞的早期阶段。从这些数据中提取的达到热平衡和化学平衡的时间尺度分别约为1/3和1.5 fm/c。因此，直接光子的大椭圆流是可以解释的。作为进一步的检验，我们还预测了2.76TeV的Pb+Pb碰撞直接光子的高次谐波，即v_3 $，v_4 $和v_5 $，以与那些声称有新的光子源来解释大的直接光子椭圆流的人竞争。
We investigated the information carried by the data of direct photons, ie, the transverse momentum spectrum and the elliptic flow $v_{2}$ from Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76TeV measured at Large Hadron Collider (LHC) and from Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV measured at Relativistic Heavy Ion Collider (RHIC), in the frame work of (3+1)-dimensional ideal hydrodynamical models constrained with hadronic data. We found those direct photon data may serve as a useful clock at the early stage of heavy ion collisions. The time scales of reaching thermal and chemical equilibrium, extracted from those data, are about 1/3 and 1.5 fm/c, respectively. Thus the large elliptic flow of direct photons is explainable. High order harmonics, ie, $v_3$, $v_4$ and $v_5$, of direct photons from Pb+Pb collisions at 2.76TeV are also predicted, as a further test to compete with those who claim new sources of photons to account for the large elliptic flow of direct photons.