论文标题
小型系统中硬散射过程的核修饰
Nuclear modification of hard scattering processes in small systems at PHENIX
论文作者
论文摘要
小型系统在RHIC上的碰撞表现出对核修饰因子$ r_ {Xa} $的重大抑制，而事件活动大的事件中的高动量中性乳头则表现出了高度抑制。这种抑制伴随着$ r_ {xa} $在活动活动较低的事件中的增强。由于事件活动通常被解释为对碰撞的中心性的量度，因此这些结果质疑对中央碰撞中抑制的任何解释，这些抑制会引起QGP产生的小型系统的能量损失。在本次演讲中，我们将将提示光子与$π^0 $的产生进行比较，而phenix在$ \ sqrt {s} = 200 \，gev $中测量的产生，以证明明显的中心依赖性与硬散射过程的核修改无关，但可能是由于偏离事件现象和集中度的偏离而导致的。此外，我们将使用D+AU中的Photon Profuct相对于P+P碰撞来确定给定事件样本的有效二进制碰撞$ N_ {Coll} $。我们发现，对于所有事件选择，除了最高事件活动的事件，$ r_ {xa} $ of $π^0 $与Unity一致。通过比较P+AU和D+AU碰撞，我们将研究剩余的抑制高$ p_ {t} $ $π^0 $生产的重要性。
Collisions of small systems at RHIC exhibit a significant suppression of the nuclear modification factor $R_{xA}$ of jets and high momentum neutral pions in events with large event activity. This suppression is accompanied by an enhancement of $R_{xA}$ in events with low event activity. Since event activity is commonly interpreted as a measure of the centrality of the collisions, these results call into question any interpretation of the suppression in central collisions that invokes energy loss in a QGP produced small systems. In this talk, we will compare prompt photon to $π^0$ production measured by PHENIX in d+Au collision at $\sqrt{s}=200\,GeV$ to demonstrate that the apparent centrality dependence is not related to a nuclear modification of hard scattering processes, but likely due to deviations from the proportionality of event activity and centrality in the underlying standard Glauber model calculations. Furthermore, we will use prompt photon production in d+Au relative to p+p collisions to empirically determine the effective number of binary collisions $N_{coll}$ of a given event sample. We find that for all event selections, except for those with the highest event activity, $R_{xA}$ of $π^0$ is consistent with unity. By comparing p+Au and d+Au collisions, we will investigate the significance of the remaining suppression of high $p_{T}$ $π^0$ production in events with high event activity.
