{"@context":"http://schema.org","@id":"https://doi.org/10.17182/hepdata.156815.v1","@reverse":{"isBasedOn":[{"@type":"ScholarlyArticle","identifier":{"@type":"PropertyValue","propertyID":"URL","value":"https://inspirehep.net/literature/2905701"}},{"@id":"https://doi.org/10.1088/1361-6633/adf7d3","@type":"JournalArticle"}]},"@type":"Dataset","additionalType":"Collection","author":{"@type":"Organization","name":"CMS Collaboration"},"creator":{"@type":"Organization","name":"CMS Collaboration"},"datePublished":"2025","description":"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 $\\text{t}\\bar{\\text{t}}$ 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.","hasPart":[{"@id":"https://doi.org/10.17182/hepdata.156815.v1/t1","@type":"Dataset","description":"Observed cross section of $\\eta_t$","name":"Observed cross section of $\\eta_t$"},{"@id":"https://doi.org/10.17182/hepdata.156815.v1/t2","@type":"Dataset","description":"Observed values of twice the negative log-likelihood with respect to the best-fit point (2dNLL) as a function of the cross...","name":"Figure 3, Parity scan"}],"identifier":[{"@type":"PropertyValue","propertyID":"HEPDataRecord","value":"https://www.hepdata.net/record/ins2905701?version=1"},{"@type":"PropertyValue","propertyID":"HEPDataRecordAlt","value":"https://www.hepdata.net/record/156815"}],"inLanguage":"en","name":"Observation of a pseudoscalar excess at the top quark pair production threshold","provider":{"@type":"Organization","name":"HEPData"},"publisher":{"@type":"Organization","name":"HEPData"},"url":"https://www.hepdata.net/record/ins2905701?version=1","version":1}