Search for Pair-Produced Vectorlike Quarks Coupling To Light Quarks in the Lepton Plus Jets Final State Using 13 Tev <i>pp</I> Collisions With the Atlas Detector

Abstract

A search is presented for the pair production of heavy vectorlike quarks (VLQs) that each decay into a W boson and a light quark. This study focuses on events where one W boson decays into leptons and the other into hadrons. The search analyzed 140 fb(-1) of pp collision data with root s = 13 TeV, recorded by the ATLAS detector from 2015 to 2018 during run 2 of the Large Hadron Collider. The final state is characterized by a high-transverse-momentum isolated electron or muon, large missing transverse momentum, multiple small-radius jets, and a single large-radius jet identified as originating from the hadronic decay of a boosted W boson. With higher center-of-mass energy and integrated luminosity than in the run 1 search, and improved analysis tools, this analysis excludes VLQs (Q) with masses below 1530 GeVat 95% confidence level for the branching ratio B(Q -> Wq) = 1, an improvement of 840 GeV on the previous ATLAS limit.