AI 中文总结
利用ATLAS探测器13和13.6 TeV数据，搜寻伴随顶夸克产生的top-philic $Z'$玻色子，未见显著信号，95%置信水平下排除质量低于1150 GeV的$Z'$（预期1250 GeV）。
AI 中文摘要
本文报道了一项对新型top-philic矢量玻色子（$Z'$）的搜寻，该玻色子与顶夸克或一对顶夸克伴随产生，并衰变为一对顶夸克。该搜寻利用了大型强子对撞机上ATLAS探测器在质心能量$\sqrt{s} =$ 13 TeV和13.6 TeV下收集的$pp$碰撞数据，对应的积分亮度分别为140 fb$^{-1}$和56 fb$^{-1}$。事件选择要求恰好包含两个同符号轻子或至少三个轻子（电子或缪子）。使用基于Transformer的分类器，该分类器以$Z'$质量为参数进行参数化，以优化信号与背景的区分度。结果在简化模型中进行解释，该模型包含一个与顶夸克耦合的色单态矢量玻色子，耦合强度为$c_t$，手征角为$\theta$。在预期标准模型背景之上未观察到显著超出。对于$c_t = 1$和$\theta = 0$的基准场景，在95%置信水平下排除了质量低于1150 GeV的$Z'$玻色子，预期排除上限为1250 GeV。
英文摘要
A search for a new top-philic vector boson ($Z'$) produced in association with a top-quark or a pair of top quarks, and decaying into a top quark pair is presented. The search uses $pp$ collision data collected by the ATLAS detector at the Large Hadron Collider at centre-of-mass energies of $\sqrt{s} =$ 13 TeV and 13.6 TeV, corresponding to integrated luminosities of 140 fb$^{-1}$ and 56 fb$^{-1}$, respectively. Events containing exactly two same-sign leptons or at least three leptons (electrons or muons) are selected. A transformer-based classifier parameterised as a function of the $Z'$ mass is used to optimise the signal-to-background discrimination. The results are interpreted in a simplified model with a colour-singlet vector boson coupled to top quarks with coupling strength $c_t$ and chirality angle $θ$. No significant excess is observed above the expected Standard Model background. A $Z'$ boson with mass below 1150 GeV is excluded at 95% confidence level for a benchmark scenario with $c_t = 1$ and $θ= 0$, with an expected limit of 1250 GeV.
CommentsComments: 48 pages in total, author list starting page 31, 8 figures, 3 tables, submitted to JHEP. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2022-44
