非对称碰撞中的中心性问题：直接光子拯救？
Centrality Issues In Asymmetric Collisions: Direct Photons To The Rescue?
摘要：
在研究大离子碰撞时，根据碰撞几何形状对实验事件进行分类的方法已经很成熟，并且没有争议。然而，RHIC和LHC的$p/d$ +A碰撞的高光度数据提供了一些令人惊讶的结果，这些结果要么需要新的物理学，要么质疑已建立的事件分类方法的适用性。到目前为止，社区中还没有达成共识，什么是正确的模型和程序来确定中心性，如何将观察到的事件活动与非常不对称的碰撞几何学联系起来，$p/d$ +A碰撞在相同的意义上，并具有与A+A相同的精度。我们认为，高$p_T$直接光子提供了对任何建议对$p/d$ +A（通常是非常不对称的）碰撞进行分类的方法的{ \it后验}测试：该方法仅在高$p_T$直接光子的核修饰因子对于所有中心性类别都是统一的情况下才是可行的。
英文摘要：
Methods to classify events experimentally according to collision geometry are well established and non-controversial when collisions of large ions are studied. However, high luminosity data from $p/d$+A collisions at RHIC and LHC provided some surprising results that either call for new physics or question the applicability of the established methods of event classification for them. So far there is no consensus in the community what is the proper model and procedure to determine centrality, how to connect observed event activity with collision geometry in very asymmetric, $p/d$+A collisions in the same sense and with the same accuracy as was done in A+A. We argue that high $p_T$ direct photons offer an {\it a posteriori} test of any method suggested to categorize $p/d$+A -- and in general, very asymmetric -- collisions: the method is only viable if the nuclear modification factor for high $p_T$ direct photons is about unity for all centrality classes.
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。
