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arXiv 1003.0194nucl-thhep-phnucl-ex
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重离子碰撞中的碰撞几何涨落和三角流

Collision geometry fluctuations and triangular flow in heavy-ion collisions

B. Alver, G. Roland

摘要:

引入了重离子碰撞中的参与者三角形和三角流的概念,类似于参与者偏心率和椭圆流的定义。参与者的三角形特征的三角形各向异性的初始核重叠的几何形状,并产生从事件的参与者核子碰撞点的事件波动。在使用多相输运模型(AMPT)的研究中,观察到三角形流信号,其与参与者的三角形成比例,并且对应于两粒子方位角关联函数中的大的第三傅立叶系数。使用两个粒子的方位角相关在大赝快度分离测量的PHOBOS和STAR实验,我们表明,这种傅立叶分量也存在于数据中。数据中的第二和第三傅立叶系数的比率表现出与AMPT计算中的中心性和横向动量的函数类似的趋势。这些研究结果表明,三角形流的山脊和广泛的数据中观察到的远侧功能的显着贡献。三角流为研究重离子碰撞中的初始碰撞几何和集体膨胀动力学提供了一种新的方法。

英文摘要:

We introduce the concepts of participant triangularity and triangular flow in heavy-ion collisions, analogous to the definitions of participant eccentricity and elliptic flow. The participant triangularity characterizes the triangular anisotropy of the initial nuclear overlap geometry and arises from event-by-event fluctuations in the participant-nucleon collision points. In studies using a multi-phase transport model (AMPT), a triangular flow signal is observed that is proportional to the participant triangularity and corresponds to a large third Fourier coefficient in two-particle azimuthal correlation functions. Using two-particle azimuthal correlations at large pseudorapidity separations measured by the PHOBOS and STAR experiments, we show that this Fourier component is also present in data. Ratios of the second and third Fourier coefficients in data exhibit similar trends as a function of centrality and transverse momentum as in AMPT calculations. These findings suggest a significant contribution of triangular flow to the ridge and broad away-side features observed in data. Triangular flow provides a new handle on the initial collision geometry and collective expansion dynamics in heavy-ion collisions.

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