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@ARTICLE{Hayrapetyan:628945,
      author       = {Hayrapetyan, Aram and others},
      collaboration = {{CMS Collaboration}},
      title        = {{O}bservation of a pseudoscalar excess at the top quark
                      pair production threshold},
      reportid     = {PUBDB-2025-01748, arXiv:2503.22382. CMS-TOP-24-007.
                      CERN-EP-2025-061},
      year         = {2025},
      note         = {Submitted to Reports on Progress in Physics. All figures
                      and tables can be found at
                      http://cms-results.web.cern.ch/cms-results/public-results/publications/TOP-24-007
                      (CMS Public Pages)},
      abstract     = {A search for resonances in top quark pair
                      ($\text{t}\bar{\text{t}}$) 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 at $\sqrt{s}$ = 13 TeV, corresponding to 138
                      fb$^{-1}$. The analysis explores the invariant mass of the
                      \ttbar 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
                      kinematic $\text{t}\bar{\text{t}}$ threshold compared to the
                      nonresonant production predicted by fixed-order perturbative
                      quantum chromodynamics (pQCD). The observed enhancement is
                      consistent with the production of a color-singlet
                      pseudoscalar ($^1$S$^{[1]}_0$) quasi-bound toponium state,
                      as predicted by nonrelativistic quantum chromodynamics.
                      Using a simplified model for $^1$S$^{[1]}_0$ toponium, the
                      cross section of the excess above the pQCD prediction is
                      measured to be 8.8$^{+1.2}_{-1.4}$ pb.},
      cin          = {CMS},
      cid          = {I:(DE-H253)CMS-20120731},
      pnm          = {611 - Fundamental Particles and Forces (POF4-611) /
                      HIDSS-0002 - DASHH: Data Science in Hamburg - Helmholtz
                      Graduate School for the Structure of Matter
                      $(2019_IVF-HIDSS-0002)$ / DFG project G:(GEPRIS)390833306 -
                      EXC 2121: Quantum Universe (390833306)},
      pid          = {G:(DE-HGF)POF4-611 / $G:(DE-HGF)2019_IVF-HIDSS-0002$ /
                      G:(GEPRIS)390833306},
      experiment   = {EXP:(DE-H253)LHC-Exp-CMS-20150101},
      typ          = {PUB:(DE-HGF)25},
      eprint       = {2503.22382},
      howpublished = {arXiv:2503.22382},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:2503.22382;\%\%$},
      doi          = {10.3204/PUBDB-2025-01748},
      url          = {https://bib-pubdb1.desy.de/record/628945},
}