{"title":"Observation of a pseudoscalar excess at the top quark pair production threshold.","authors":"The Cms Collaboration","doi":"10.1088/1361-6633/adf7d3","DOIUrl":null,"url":null,"abstract":"<p><p>A search for resonances in top quark pair (tt-) production in final states with two charged leptons and multiple jets is presented, based on proton-proton collision data collected by the CMS experiment at the CERN LHC ats=13TeV, corresponding to 138 fb<sup>-1</sup>. The analysis explores the invariant mass of thett-system and two angular observables that provide direct access to the correlation of top quark and antiquark spins. A significant excess of events is observed near the kinematictt-threshold compared to the non-resonant production predicted by fixed-order perturbative quantum chromodynamics (pQCD). The observed enhancement is consistent with the production of a color-singlet pseudoscalar (1S0[1]) quasi-bound toponium state, as predicted by non-relativistic quantum chromodynamics. Using a simplified model for1S0[1]toponium, the cross section of the excess above the pQCD prediction is measured to be8.8-1.4+1.2pb.</p>","PeriodicalId":74666,"journal":{"name":"Reports on progress in physics. Physical Society (Great Britain)","volume":" ","pages":""},"PeriodicalIF":20.7000,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Reports on progress in physics. Physical Society (Great Britain)","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1088/1361-6633/adf7d3","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
A search for resonances in top quark pair (tt-) production in final states with two charged leptons and multiple jets is presented, based on proton-proton collision data collected by the CMS experiment at the CERN LHC ats=13TeV, corresponding to 138 fb-1. The analysis explores the invariant mass of thett-system and two angular observables that provide direct access to the correlation of top quark and antiquark spins. A significant excess of events is observed near the kinematictt-threshold compared to the non-resonant production predicted by fixed-order perturbative quantum chromodynamics (pQCD). The observed enhancement is consistent with the production of a color-singlet pseudoscalar (1S0[1]) quasi-bound toponium state, as predicted by non-relativistic quantum chromodynamics. Using a simplified model for1S0[1]toponium, the cross section of the excess above the pQCD prediction is measured to be8.8-1.4+1.2pb.
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