A Search for Di-Leptonic Final State Vector-Like Quark Pair Production in 13 TeV $pp$ Collisions Using CMS Data

We describe a search for the production of a pair of Bottom-type ($B\overline{B}$) Vector-Like Quarks (VLQ’s) with masses greater than 900 GeV in a di-leptonic final state in proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the CMS Experiment. The analysis is based on the detection of a di-lepton pair from the decay of a $Z$ boson and is sensitive to events in which one VLQ decays to a $b$ quark and a $Z$ boson and the other to a $b$ quark and either a $Z$ or a Higgs boson. Requiring that the event kinematics are consistent with a di-leptonic $Z$ decay, with either a $Z$ or Higgs decaying to jets and that the reconstructed VLQ’s have equal masses greatly reduces the background from Standard Model processes. We use a $\chi^2$ metric based on the Higgs or $Z$ mass and the equality of the two VLQ masses to select the correct combinations of jets. Since for a highly boosted Higgs or $Z$ the two jets resulting from the daughter quarks might be merged, we carry out independent analyses depending on the number of observed jets. We present the expected exclusion limits using 137 fb$^{-1}$ of integrated luminosity collected by CMS during 2016, 2017 and 2018 run periods.