Search for bottom-type vectorlike quark pair production in dileptonic and fully hadronic final states in proton-proton collisions at √s = 13 TeV

A search is described for the production of a pair of bottom-type vectorlike quarks (B VLQs) with mass greater than 1000 GeV. Each B VLQ decays into a 𝑏 quark and a Higgs boson, a b quark and a 𝑍 boson, or a t quark and a W boson. This analysis considers both fully hadronic final states and those containing a charged lepton pair from a Z boson decay. The products of the H → bb boson decay and of the hadronic Z or W boson decays can be resolved as two distinct jets or merged into a single jet, so the final states are classified by the number of reconstructed jets. The analysis uses data corresponding to an integrated luminosity of 138 fb⁻¹ collected in proton-proton collisions at √s = 13 TeV with the CMS detector at the LHC from 2016 to 2018. No excess over the expected background is observed. Lower limits are set on the B VLQ mass at the 95% confidence level. These depend on the B VLQ branching fractions and are 1570 and 1540 GeV for 100% B → bH and 100% B → bZ, respectively. In most cases, the mass limits obtained exceed previous limits by at least 100 GeV.