Search for pair production of vector-like quarks in leptonic final states in proton-proton collisions at √s = 13 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 13TeV. Data were collected by the CMS experiment at the CERN LHC in 2016-2018, with an integrated luminosity of 138 fb(-1). Events are separated into single-lepton, same-sign charge dilepton, and multilepton channels. In the analysis of the single-lepton channel a multilayer neural network and jet identification techniques are employed to select signal events, while the same-sign dilepton and multilepton channels rely on the high-energy signature of the signal to distinguish it from standard model backgrounds. The data are consistent with standard model background predictions, and the production of vector-like quark pairs is excluded at 95% confidence level for T quark masses up to 1.54TeV and B quark masses up to 1.56TeV, depending on the branching fractions assumed, with maximal sensitivity to decay modes that include multiple top quarks. The limits obtained in this search are the strongest limits to date for t-tbar production, excluding masses below 1.48TeV for all decays to third generation quarks, and are the strongest limits to date for b-bbar production with b quark decays to tW.