单轻子道中顶夸克对产生阈值处超出事例的观测
Observation of an excess at the top quark pair production threshold in the single-lepton channel
浏览论文内容
中文总结 AI 辅助
CMS实验利用138 fb⁻¹的13 TeV质子-质子碰撞数据，在单轻子道观测到顶夸克对产生阈值处的显著事例超出，为双轻子道的相关结果提供独立确认。
中文摘要 AI 辅助
本研究针对顶夸克-反顶夸克（$\rm t\bar{t}$）类束缚态“toponium”开展搜索，该状态位于运动学$\rm t\bar{t}$产生阈值附近，末态包含单个电子或μ子及喷注。研究使用欧洲核子研究中心（CERN）大型强子对撞机（LHC）的CMS实验采集的质心系能量$\rm \boldsymbol{\textit{s}} = 13\rm \thinspace TeV$的质子-质子碰撞数据，对应积分亮度为$\rm 138\rm \thinspace fb^{-1}$。分析考察顶夸克与反顶夸克的相对速度，以及两个对$\rm t\bar{t}$系统的宇称和自旋敏感的角观测量。与微扰量子色动力学（QCD）次领头阶计算的标准模型$\rm t\bar{t}$产生预言相比，观测到显著的事例超出，该超出对应的观测总截面为$\rm 5.1\rm \thinspace \boldsymbol{\textit{\textpm}} \rm 0.9\rm \thinspace pb$，且与非相对论QCD启发的色单态赝标量toponium简化模型相符，观测显著性达6.1个标准偏差。该结果对双轻子道报道的超出事例提供了独立确认。
英文摘要
A search is presented for top quark-antiquark ($\mathrm{t\bar{t}}$) quasi-bound ``toponium'' states, near the kinematic $\mathrm{t\bar{t}}$ production threshold in final states with a single electron or muon and jets. The study uses proton-proton collision data at $\sqrt{s}$ = 13 TeV, collected by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 138 fb$^{-1}$. The analysis examines the relative velocity between the top quark and antiquark, along with two angular observables sensitive to the parity and spin of the $\mathrm{t\bar{t}}$ system. A significant excess of events is observed relative to the standard model prediction for $\mathrm{t\bar{t}}$ production calculated at next-to-next-to-leading order in perturbative quantum chromodynamics (QCD). The excess corresponds to an observed total cross section of 5.1$\pm$0.9 pb and is consistent with a simplified model of a color singlet pseudoscalar toponium motivated by nonrelativistic QCD, with a resulting observed significance of 6.1 standard deviations. The result provides an independent confirmation of the excess reported in the dilepton channel.
