Search for a Light Charged Higgs Boson in T → H±b Decays, With H±→ Cs, in Pp Collisions at √s=13 Tev With the Atlas Detector

Abstract

A search for a light charged Higgs boson produced in decays of the top quark, t -> H(+/-)b with H-+/- -> cs, is presented. This search targets the production of top-quark pairs t (t) over bar. WbH(+/-)b, with W -> lv (l = e, mu), resulting in a lepton-plus-jets final state characterised by an isolated electron or muon and at least four jets. The search exploits b-quark and c-quark identification techniques as well as multivariate methods to suppress the dominant t (t) over bar background. The data analysed correspond to 140 fb(-1) of pp collisions at root s = 13 TeV recorded with the ATLAS detector at the LHC between 2015 and 2018. Observed (expected) 95% confidence-level upper limits on the branching fraction B(t -> H(+/-)b), assuming B(t -> Wb) + B(t -> H +/-(-> cs)b) = 1.0, are set between 0.066% (0.077%) and 3.6% (2.3%) for a charged Higgs boson with a mass between 60 and 168 GeV.