Combination of searches for singly produced vector-like top quarks in pp collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

Abstract

A combination of searches for the single production of vector-like top quarks ($T$) is presented. These analyses are based on proton$-$proton collisions at $\sqrt{s}=13$ TeV recorded in 2015$-$2018 with the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb${}^{-1}$. The $T$-quark decay modes considered in this combination are into a top quark and either a Standard Model Higgs boson or a $Z$ boson ($T\to Ht$ and $T\to Zt$). The individual searches used in the combination are differentiated by the number of leptons ($e$, $\mu$) in the final state. The observed data are found to be in good agreement with the Standard Model background prediction. Interpretations are provided for a range of masses and couplings of the vector-like top quark for benchmark models and generalized representations in terms of 95% confidence level limits. For a benchmark signal prediction of a vector-like top quark SU2 singlet with electroweak coupling, $\kappa$, of 0.5, masses below 2.1 TeV are excluded, resulting in the most restrictive limits to date.

43 pages in total, author list starting page 26, 7 figures, 5 tables, published in PRD. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2021-02/

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• Search for charged Higgs bosons through vector-like top quark pair production at the LHC
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