Search for pair production of vector-like quarks in leptonic final states at $\sqrt{s}=13~\mathrm{TeV}$

A search is presented for vector-like T and B quark-antiquark pairs produced in proton-proton collisions at a center-of-mass energy of $13~\mathrm{TeV}$. Data were collected by the CMS Experiment in 2016, 2017, and 2018, with an integrated luminosity of $137~\mathrm{fb}^{-1}$. Events with leptonic signatures are selected: one electron or muon, missing transverse energy, and at least three large-radius jets in the single-lepton channel; two electrons or muons with matching electric charge in the same-sign dilepton channel; and three or more electrons or muons in the multilepton channel. The single-lepton channel utilizes a multilayer neural network and jet identification techniques to discriminate signal events, while the same-sign dilepton and multilepton channels rely on the high-energy signature of the signal to distinguish it from rare standard model backgrounds. The production of vector-like quark pairs is excluded for T quark masses up to $1.54~\mathrm{TeV}$ and B quark masses up to $1.56~\mathrm{TeV}$ depending on the branching fractions assumed, with maximal sensitivity to decay modes that include multiple top quarks. These are the strongest limits to date for $\mathrm{T\overline{T}}$ production with decays to tH and bW and $\mathrm{B\overline{B}}$ production with decays to tW.