Search for bottom-type vectorlike quark pair production in dileptonic and fully hadronic final states in proton-proton collisions at $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$

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 $H\to bb$ 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 $138\text{}\text{}{\mathrm{fb}}^{-1}$ collected in proton-proton collisions at $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$ 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% $B\to bH$ and 100% $B\to bZ$, respectively. In most cases, the mass limits obtained exceed previous limits by at least 100 GeV.