2025 Articles

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

Al Khoury, Konie; Angerami, Aaron; Brooijmans, Gustaaf H.; Cole, Brian A.; Busch, Elena Laura

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 𝑡𝑡̄ → 𝑊𝑏𝐻±𝑏, with 𝑊 → 𝓁𝜈 (𝓁 = 𝑒,𝜇), 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 𝑡𝑡̄ background.

The data analysed correspond to 140 fb⁻¹ of 𝑝𝑝 collisions at √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.