Speaker
Description
A search is made for a vector-like $T$ quark decaying into a Higgs boson and a top quark in 13 TeV proton-proton collisions using the ATLAS detector at the Large Hadron Collider with a data sample corresponding to an integrated luminosity of $139\rm~^{-1}$. The all-hadronic decay modes $H\to b\bar{b}$ and $t\to bW\to bq\bar{q'}$ are reconstructed as large-radius jets and identified using tagging algorithms. Improvements in background estimation, signal discrimination, and a larger data sample, contribute to an improvement in sensitivity over previous all-hadronic searches. No significant excess is observed above the background, so limits are set on the production cross-section of a singlet $T$ quark at 95\% confidence level, depending on the mass, $m_T$, and coupling, $κ_T$, of the vector-like $T$ quark to Standard Model particles. This search targets a mass range between 1.0 to 2.3 TeV, and a coupling value between 0.1 to 1.6, expanding the phase space of previous searches. In the considered mass range, the upper limit on the allowed coupling values increases with $m_T$ from a minimum value of 0.35 for $1.07 \lt m_T \lt 1.4\rm~ TeV$ up to 1.6 for $m_T=2.3\rm~TeV$.
