Four models for the initial conditions of a fluid dynamic description of high energy heavy ion collisions are analysed and compared. We study expectation values and event-by-event fluctuations in the initial transverse energy density profiles from Pb-Pb collisions. Specifically, introducing a Fourier-Bessel mode expansion for fluctuations, we determine expectation values and two-mode correlation functions of the expansion coefficients. The analytically solveable independent point-sources model is compared to an initial state model based on Glauber theory and two models based on the Color Glass Condensate framework. We find that the large wavelength modes of all investigated models show universal properties for central collisions and also discuss to which extent general properties of initial conditions can be understood analytically.

中文翻译：

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高能重离子碰撞初始密度波动模型比较

分析和比较了高能重离子碰撞的流体动力学描述初始条件的四种模型。我们研究了铅-铅碰撞的初始横向能量密度分布中的期望值和逐个事件的波动。具体来说，引入波动的傅立叶-贝塞尔模式展开，我们确定展开系数的期望值和双模式相关函数。将解析可解的独立点源模型与基于 Glauber 理论的初始状态模型和基于彩色玻璃冷凝物框架的两个模型进行比较。我们发现所有研究模型的大波长模式都显示出中心碰撞的普遍特性，并且还讨论了在多大程度上可以分析地理解初始条件的一般特性。