Search for single production of a vector-like $T$ quark decaying into a Higgs boson and top quark with fully hadronic final states using the ATLAS detector

TL;DR

This paper reports a search for vector-like T quarks decaying into Higgs bosons and top quarks in fully hadronic final states using ATLAS data, setting limits on production cross-section and coupling for masses 1.0-2.3 TeV.

Contribution

First search to analyze fully hadronic decay modes of T quarks at 13 TeV with ATLAS, establishing new limits on coupling and mass.

Findings

No significant excess observed over background.

Limits set on T quark production cross-section and coupling.

Coupling limits increase with T quark mass from 0.35 to 1.6.

Abstract

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 fb$^{-1}$. The Higgs-boson and top-quark candidates are identified in the all-hadronic decay mode, where $H\to b\bar{b}$ and $t\to b W \to b q \bar{q}^\prime$ are reconstructed as large-radius jets. The candidate Higgs boson, top quark, and associated B-hadrons are identified using tagging algorithms. 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, $\kappa_T$, of the vector-like $T$ quark to Standard Model particles. In the considered mass range between 1.0 and 2.3 TeV, the upper limit on the allowed coupling values increases with $m_T$ from a minimum value of 0.35 for 1.07 < $m_T$ < 1.4 TeV to 1.6 for $m_T$ = 2.3 TeV.