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 ($B\bar{B}$) vector-like quarks (VLQ’s) with masses greater than 900 GeV in a di-lepton final state using data from 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 modified-$\chi^2$ procedure 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 to a single jet, we carry out two independent analyses depending on the number of observed jets. We present the expected exclusion limits from the combined analyses corresponding to 137 fb$^{-1}$ of integrated luminosity collected by CMS during 2016, 2017, and 2018 run period.