标题： 用光子标记的喷注揭示高能核碰撞中的喷流角扩展 显示英文标题

标题： Unveiling the jet angular broadening with photon-tagged jets in high-energy nuclear collisions

摘要： 高密度核物质中喷淋子结构的介质修饰近年来引起了重离子物理领域的极大兴趣。对单举喷淋的测量显示，在原子核-原子核碰撞中存在角向收窄现象，而最近CMS对光子标记喷淋（$\gamma$+喷淋）的结果则表明存在展宽的证据。在这项研究中，我们采用一种传输方法，对该介质中夸克-胶子等离子体的能量损失和介质响应进行理论分析，以研究单举喷淋和$\gamma$+喷淋的角结构。我们检查了在$0-30\%$能量下铅-铅碰撞（$\sqrt{s_{NN}} = 5.02$TeV）中$\gamma$+喷淋的周长修改，并与最近的CMS测量结果取得了良好的一致性。我们通过改变$x_{j\gamma} = p_T^{\rm jet}/p_T^{\gamma}$的阈值来探索选择偏差与喷淋动力学之间的关系。值得注意的是，我们定量地证明了$\gamma$+喷淋显著减少了选择偏差，可以有效地选择在铅-铅碰撞中被充分淬灭的喷淋，这对于捕获喷淋角展宽至关重要。此外，我们还估计了介质诱导的胶子辐射和介质响应对喷淋角子结构展宽的贡献。 最后，我们分析了PbPb碰撞中喷注$R_g$和$\Delta R_{\rm axis}$的修改模式，结果显示$\gamma$+喷注有轻微展宽，而相对于pp碰撞，全 inclusively 的喷注则表现出显著的收窄。 显示英文摘要

摘要： The medium modification of jet substructure in hot and dense nuclear matter has garnered significant interest from the heavy-ion physics community in recent years. Measurements of inclusive jets show an angular narrowing in nucleus-nucleus collisions, while recent CMS results for photon-tagged jets ($\gamma$+jets) suggest evidence of broadening. In this study, we conduct a theoretical analysis of the angular structure of inclusive jets and $\gamma$+jets using a transport approach that accounts for jet energy loss and the medium response in the quark-gluon plasma. We examine the girth modification of $\gamma$+jets in $0-30\%$ PbPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV, achieving satisfactory agreement with recent CMS measurements. We explore the relationship between selection bias and jet kinematics by varying the threshold for $x_{j\gamma} = p_T^{\rm jet}/p_T^{\gamma}$. Notably, we quantitatively demonstrate that $\gamma$+jets significantly reduce selection bias and can effectively select jets that have been sufficiently quenched in PbPb collisions, which is crucial for capture the jet angular broadening. Additionally, we estimate the contributions of medium-induced gluon radiation and the medium response to the broadening of the jet angular substructure. Lastly, we analyze the modification patterns of jet $R_g$ and $\Delta R_{\rm axis}$ in PbPb collisions, which indicate slight broadening for $\gamma$+jets and noticeable narrowing for inclusive jets compared to pp collisions.