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

Abstract

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 →𝑏⁢𝑏 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 →𝑏⁢𝐻 and 100% 𝐵 →𝑏⁢𝑍, respectively. In most cases, the mass limits obtained exceed previous limits by at least 100 GeV.