利用γ+喷注量化重离子碰撞中介质诱导的喷注展宽
Using $γ$+jets to quantify medium-induced jet broadening in heavy-ion collisions
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中文总结 AI 辅助
研究重离子碰撞中利用γ+喷注量化介质诱导喷注展宽，通过JEWEL事件发生器，以大R值γ+喷注为基线，用小半径喷注聚类成修剪喷注代替大半径喷注，量化其恢复展宽信号程度及相关依赖性，为喷注-介质相互作用实验研究提供指导。
中文摘要 AI 辅助
高能核-核碰撞中产生的喷注结构携带了夸克-胶子等离子体中部分子能量损失和相互作用的信息。部分子能量损失导致喷注横向动量迁移，在包容性喷注测量中产生选择偏差。我们使用JEWEL事件发生器，研究一种以实验可行的方式减少选择偏差并获取介质诱导喷注展宽的策略。首先考虑大R值的γ+喷注事件作为基线，其选择偏差小且显示出喷注周长中介质诱导展宽的明显信号，但大R值在实验中因重离子碰撞中潜在事件波动大而无法获取。因此重新聚类小半径（\(r_{\rm sub}\)=0.2）喷注作为大半径（R = 1.2）喷注的代理，即修剪喷注。量化修剪喷注恢复喷注展宽信号的程度，并研究其对子喷注锥大小和最小横向动量的依赖性。研究子喷注的内部结构以揭示喷注淬火对不同子喷注配置的依赖性，发现1个子喷注配置的PbPb喷注有强烈变窄，次领先子喷注有介质诱导展宽的明显特征。喷注径向轮廓表明介质诱导展宽的贡献与质子-质子碰撞中的辐射不同。这些贡献用修剪程序不易恢复，但在单个子喷注配置中考虑子喷注半径之外的轮廓时会显著增强。这为未来利用重离子碰撞中γ+喷注进行喷注-介质相互作用的实验研究提供了指导。
英文摘要
The structure of jets produced in high-energy nucleus-nucleus collisions carries information on parton energy loss and interaction in the quark-gluon plasma. This parton energy loss results in migration of jets in terms of transverse momentum, leading to a selection bias in inclusive jet measurements. Using the JEWEL event generator, we investigate a strategy to reduce selection bias and access medium-induced jet broadening, in an experimentally viable way. As a baseline, we first consider large-R $γ$+jet events, with little selection bias, which show a clear signal of medium-induced broadening in the jet girth. However, large-R is experimentally inaccessible due to the large underlying event fluctuations in heavy-ion collisions, so we re-cluster a collection of small-radius ($r_{\rm sub}$ = 0.2) jets as a proxy for the large-radius (R = 1.2) jet, which we refer to as a trimmed jet. We quantify to what extent trimmed jets recover signals of jet broadening and investigate its dependence on the subjet cone size and the minimum transverse momentum. We study the internal structure of the subjets to expose the dependence of jet quenching on different subjet configurations, finding a strong narrowing of PbPb jets for the 1-subjet configurations, and a visible signature of medium-induced broadening for sub-leading subjets. The jet radial profile reveals that contributions from medium-induced broadening are distinct from radiation in pp collisions. These contributions are not easily recovered using our trimming procedure, but are substantially enhanced in single-subjet configurations when considering the profile \emph{beyond} the subjet radius. This provides guidance for future experimental studies of jet-medium interactions using $γ$+jet in heavy-ion collisions.
