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从二维角关联计算$v_2$测量的普适中心性和碰撞能量趋势

Universal Centrality and Collision Energy Trends for $v_2$ Measurements From 2D Angular Correlations

STAR collaboration, David Kettler

备注：
Conference proceedings from Hot Quarks 2008. 6 pages, 8 figures
发表信息：
The European Physical Journal C: Volume 62, Issue1 (2009), Page 175
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摘要：

我们测量了$p_t$积分四极分量的两粒子方位角相关（与量$v_2$有关，在这种情况下表示为$v_2 \{2D\}$）通过二维（2D）角自相关$(η, ϕ)$在62和200 GeV的金-金碰撞中的未识别强子。2D自相关提供了一种方法，以去除对$v_2$的非四极贡献（通常称为"非流动“），假设这种过程在检测器接受度内对成对相对$η$产生显著依赖性。我们假设，根据经验观察，非四极贡献占主导地位的微型射流或最小偏置射流。使用光学Glauber偏心模型的初始状态的几何形状，我们发现简单而准确的普遍的四极分量的能量和中心的趋势。中心性趋势仅由初始状态（碰撞参数$b$和质心能量$\sqrt{s_{NN}}$）确定。没有明显的依赖于不断演变的系统动态（例如，状态方程或二次碰撞数）。我们的测量的四极和非四极组件的影响的贡献$v_2$。他们认为，$v_2 \{2\}$和$v_2 \{4\}$（或$v_2 \{2D\}$）之间差异的主要来源是微型射流的测量特性。

英文摘要：

We have measured the $p_t$-integrated quadrupole component of two-particle azimuth correlations (related to quantity $v_2$, denoted in this case by $v_2 \{2D\}$) via two-dimensional (2D) angular autocorrelations on $(η, ϕ)$ for unidentified hadrons in Au-Au collisions at 62 and 200 GeV. The 2D autocorrelation provides a method to remove non-quadrupole contributions to $v_2$ (conventionally termed ``nonflow'') under the assumption that such processes produce significant dependence on pair-wise relative $η$ within the detector acceptance. We hypothesize, based on empirical observations, that non-quadrupole contributions are dominated by minijets or minimum-bias jets. Using the optical Glauber eccentricity model for initial-state geometry we find simple and accurate universal energy and centrality trends for the quadrupole component. Centrality trends are determined only by the initial state (impact parameter $b$ and center-of-mass energy $\sqrt{s_{NN}}$). There is no apparent dependence on evolving system dynamics (e.g., equation of state or number of secondary collisions). Our measurements of the quadrupole and non-quadrupole components have implications for the contributions to $v_2$. They suggest that the main source of the difference between $v_2 \{2\}$ and $v_2 \{4\}$ (or $v_2 \{2D\}$) is measured properties of minijets.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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