Search for Pair Production of Vector-Like Quarks in the Fully Hadronic Channel

The results of two searches for vector-like T or B quark pair production using the fully hadronic final state are presented, using data from the CMS experiment at a center of mass energy of 13 TeV collected during the 2016 run, corresponding to an integrated luminosity of $35.9~\mathrm{fb}^{-1}$. A multiclassification algorithm, the ``boosted event shape tagger'', is deployed to label candidate jets as originating from top quarks, W, Z, or Higgs bosons. Candidate events are categorized according to the multiplicities of heavy objects observed in the final state, and the scalar sum of all observed jet momenta is used to discriminate signal events from the QCD multijet background. This novel strategy is complemented by a second, cut-based analysis that specifically targets the bW decay mode of the T quark, and allows for the reconstruction of the T quark candidates, providing additional sensitivity. Both analyses probe all possible branching fraction combinations of the T and B quarks and set limits on their masses, ranging from 740 to 1370 GeV. These results represent a significant improvement relative to existing searches in the fully hadronic final state.