Search for pair-production of vector-like quarks in lepton plus jets final states containing at least one <i>b</i>-tagged jet using the Run 2 data from the ATLAS experiment

Abstract

<p>A search is presented for the pair-production of heavy vector-like quarks in the lepton+jets final state using 140 fb⁻¹ of proton–proton collisions at �=13 TeV collected with the ATLAS detector. The search is optimised for vector-like top-quarks (<em>T</em>) that decay into a <em>W</em> boson and a <em>b</em>-quark, with one <em>W</em> boson decaying leptonically and the other hadronically. Other vector-like quark flavours and decay modes are also considered. Events are selected with one high transverse-momentum electron or <a href="https://www.sciencedirect.com/topics/physics-and-astronomy/muon" title="Learn more about muon from ScienceDirect's AI-generated Topic Pages">muon</a>, large missing <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/transverse-momentum" title="Learn more about transverse momentum from ScienceDirect's AI-generated Topic Pages">transverse momentum</a>, a large-radius jet identified as a <em>W</em> boson, and multiple small-radius jets, at least one of which is <em>b</em>-tagged. Vector-like <em>T</em>-quarks with 100% branching ratio to <em>Wb</em> are excluded at 95% CL for masses below 1700 GeV. These limits are also applied to vector-like <em>Y</em>-quarks, which decay exclusively into a <em>W</em> boson and a <em>b</em>-quark. Isospin singlets with �(�→��:��:��)=1/2:1/4:1/4 are excluded for masses below 1360 GeV.</p><ul><li><br></li></ul>