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Description
A search for new particles decaying to top quark-antiquark pairs is performed using proton-proton collision data at a centre-of-mass energy of 13 TeV. The data set recorded with the CMS detector between 2016 and 2018 is used, corresponding to an integrated luminosity of 138 fb − 1 −1 . Final states with 0, 1, and 2 leptons are analyzed, covering all decay modes of the top quark-antiquark pairs. Heavy Z' bosons with relative widths of 1, 10, and 30% are excluded for masses in the ranges 0.4 − −4.8, 0.4 − −6.2, and 0.4 − −7.4 TeV, respectively. A Kaluza − −Klein gluon in the Randall − −Sundrum model and a dark-matter mediator are excluded for masses between 0.5 − −5.5 and 1.0 − −4.2 TeV, respectively. These results set the most stringent limits to date for the considered models in the t t ˉ t t ˉ final state. In addition, in the two-Higgs-doublet models, upper limits are set on the coupling strength modifier for scalar and pseudoscalar Higgs bosons with relative widths of 2.5, 10, and 25% in the mass range of 0.5 − −1.0 TeV.