Search for Vector-like Quarks in the All-hadronic Decay Channel using the ATLAS Detector

Abstract

A search is made for a vector-like top quark partner T decaying hadronically to a Standard Model top quark and a Higgs boson in $\sqrt{s} = 13$ TeV proton-proton collisions at the Large Hadron Collider. The data sample corresponds to an integrated luminosity of 139 fb$^{-1}$ collected by the ATLAS detector. The decaying $H \rightarrow b\bar{b}$ and $t \rightarrow bW \rightarrow bq\bar{q}'$ are reconstructed as large-radius jets. Candidate Higgs bosons, top quarks, and associated $B$-hadrons are identified using tagging algorithms. No significant excess is observed above the Standard Model background. Limits are set on the production cross-section of a singlet $T$ quark at 95% confidence level, depending on the mass of the $T$ quark, $m_{T}$, and its coupling strength to Standard Model particles, $\kappa_{T}$. In the considered mass range between 1.0 and 2.3 TeV, the upper limit on allowed coupling values increases with $m_{T}$, up to $m_{T} = 1.7$ TeV at $\kappa_{T} = 0.7$.