Aad, G.Abbott, B.Abbott, D.C.Abed Abud, A.Abeling, K.Abhayasinghe, D.K.Abidi, S.H.Aboulhorma, A.Abramowicz, H.Abreu, H.Abulaiti, Y.Abusleme Hoffman, A.C.Acharya, B.S.Achkar, B.Adam, L.Adam Bourdarios, C.Adamczyk, L.Adamek, L.Addepalli, S.V.Adelman, J.et al.2022-07-122022-07-122022Physical Review D, 2022; 105(9):092012-1-092012-342470-00102470-0029https://hdl.handle.net/2440/135784A search is made for a vectorlike 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→bb¯ and t→bW→bqq¯′ 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 mT and coupling κT of the vectorlike 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 mT from a minimum value of 0.35 for 1.07<mT<1.4 TeV to 1.6 for mT=2.3 TeV.en© 2022 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Journal article10.1103/PhysRevD.105.0920122022-07-12600616Ting, E.X.L. [0000-0002-5886-6339]Potti, H. [0000-0002-0800-9902]White, M.J. [0000-0001-5474-4580]Jackson, P. [0000-0002-0847-402X]