在质心系能量为13 TeV的质子-质子碰撞中利用有效场论方法寻找多轻子末态中的顶夸克味变中性流
Search for top quark flavor-changing neutral currents in multilepton final states using an effective field theory approach in proton--proton collisions at $\sqrt{s}$ = 13 TeV
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中文总结 AI 辅助
在13 TeV质子-质子碰撞中，利用CMS的138 fb⁻¹数据，通过有效场论方法首次全局搜索顶夸克味变中性流，未发现相关证据，对相关算符及衰变分支比给出迄今最严限制。
中文摘要 AI 辅助
我们对顶夸克产生和衰变过程中涉及的味变中性流（FCNC）相互作用开展了一项寻找研究。该分析在标准模型有效场论框架下，首次在顶夸克FCNC领域建立了全局搜索，通过对数据的单次拟合同时约束所有相关算符，为大型强子对撞机（LHC）的未来测量与组合提供了框架。本分析使用CMS探测器采集的质心系能量为13 TeV的质子-质子碰撞数据，对应积分亮度为138 fb⁻¹。我们在含两个同号带电轻子或三个轻子的末态中探测信号贡献，采用多变量判别量区分信号与本底，其分布输入似然拟合以确定24个威尔逊系数的95%置信区间。未观测到FCNC相互作用的证据，这些结果首次对完整算符集进行了同时约束，并对通过两夸克-两轻子相互作用的顶夸克FCNC衰变分支比给出了迄今为止最严格的限制。
英文摘要
We present a search for flavor-changing neutral current (FCNC) interactions involving the top quark in production and decay. This analysis establishes the first global search in the top quark FCNC sector within the standard model effective field theory where all relevant operators are constrained simultaneously in a single fit to data, providing a framework for future measurements and combinations at the LHC. The analysis uses proton$-$proton collision data collected at $\sqrt{s}$ = 13 TeV by the CMS detector, corresponding to an integrated luminosity of 138 fb$^{-1}$. Signal contributions are probed in final states with two same-sign charged leptons or three leptons. Multivariate discriminants are used to separate signal from background, and their distributions enter a likelihood fit to determine 95% confidence intervals for 24 Wilson coefficients. No evidence for FCNC interactions is observed. These results provide the first simultaneous constraints on the complete operator set and place the most stringent limits to date on FCNC top quark decay branching fractions via two-quark$-$two-lepton interactions.
