Search for a heavy charged Higgs boson decaying into a $\textit{W}$ boson and a Higgs boson in final states with leptons and $\textit{b}$-jets in = 13 TeV $\textit{pp}$ collisions with the ATLAS detector

This article presents a search for a heavy charged Higgs boson produced in association with a top quark and a bottom quark, and decaying into a $\textit{W}$ boson and a 125 GeV Higgs boson $\textit{h}$. The search is performed in final states with one charged lepton, missing transverse momentum, and jets using proton-proton collision data at = 13 TeV recorded with the ATLAS detector during Run 2 of the LHC at CERN. This data set corresponds to a total integrated luminosity of 140 fb . The search is conducted by examining the reconstructed invariant mass distribution of the $\textit{Wh}$ candidates for evidence of a localised excess in the charged Higgs boson mass range from 250 GeV to 3 TeV. No significant excess of data over the expected background is observed and 95% confidence-level upper limits between 2.8 pb and 1.2 fb are placed on the production cross-section times branching ratio for charged Higgs bosons decaying into $\textit{Wh}$.