Search for pair-produced vector-like top quarks decaying into Lorentz-boosted top quarks and scalar bosons in proton-proton collisions at $\sqrt{s}$ = 13 TeV

Abstract

A search for pair-produced vector-like top quarks, T, decaying into a new scalar boson $ϕ$ and a standard model (SM) top quark is presented. The search targets events containing a photon pair originating from the decay of one of the scalar bosons, accompanied by all-hadronic decays of the SM top quark pair. The analysis is optimized for boosted top quark signatures in which the decay products of the top quarks are reconstructed as large-radius jets. The search is based on proton-proton collision data at $\sqrt{s}$ = 13 TeV, collected by the CMS experiment at the CERN LHC during 2016$-$2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The search is performed for an array of T and $ϕ$ masses. No significant deviation from the predicted background is observed. The largest local excess has a significance of 2.7 standard deviations, reduced to 1.5 standard deviations after accounting for the look-elsewhere effect. Upper limits at 95% confidence level are set on the product of $\mathrm{T\bar{T}}$ production cross section and the branching fraction.