Breaking of factorization of two-particle correlations in hydrodynamics
Breaking of factorization of two-particle correlations in hydrodynamics
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DOI：
10.1103/physrevc.87.031901
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发表时间：
2012-11
影响因子：
3.1
通讯作者：
F. Gardim;F. Grassi;M. Luzum;J. Ollitrault
中科院分区：
文献类型：
--
作者：
F. Gardim;F. Grassi;M. Luzum;J. Ollitrault
在超相对论重离子碰撞中形成的系统表现为接近完美的流体。这种集体行为通过两粒子方位角相关性进行实验探测，这通常是对每对粒子中一个粒子的属性进行平均。在这封信中，我们认为，许多额外的信息包含在相关性的详细结构。特别是，相关矩阵表现出近似因式分解的横向动量，这是作为一个强有力的证据的水动力图片，而从因式分解形式的偏差被视为信号的内在，“非流动”的相关性。我们表明，流体力学实际上预测分解打破作为一个自然的后果，初始状态的波动和平均的事件。我们推导出一般的不等式关系，如果流量占主导地位，这是饱和的，如果矩阵分解。对于横动量高达5 GeV，这些不等式满足的数据，但不饱和。我们发现至少大分解打破事件的理想流体动力学计算的数据，并认为这种现象打开了一个新的窗口，研究初始波动。
The system formed in ultrarelativistic heavy-ion collisions behaves as a nearly-perfect fluid. This collective behavior is probed experimentally by two-particle azimuthal correlations, which are typically averaged over the properties of one particle in each pair. In this Letter, we argue that much additional information is contained in the detailed structure of the correlation. In particular, the correlation matrix exhibits an approximate factorization in transverse momentum, which is taken as a strong evidence for the hydrodynamic picture, while deviations from the factorized form are taken as a signal of intrinsic, "nonflow" correlations. We show that hydrodynamics in fact predicts factorization breaking as a natural consequence of initial state fluctuations and averaging over events. We derive the general inequality relations that hold if flow dominates, and which are saturated if the matrix factorizes. For transverse momenta up to 5 GeV, these inequalities are satisfied in data, but not saturated. We find at least as large factorization breaking in event-by-event ideal hydrodynamic calculations as in data, and argue that this phenomenon opens a new window on the study of initial fluctuations.