Signature of a light charged Higgs boson from top quark pairs at the LHC

Abstract

The charged Higgs boson is a smoking gun of extensions of the standard model with multiple Higgs doublets, and has been searched for at various collider experiments. In this paper, we study the signature of a light charged Higgs boson produced by top quark pairs at the Large Hadron Collider (LHC), with subsequent three-body decays into a $W$ boson and a pair of bottom quarks. Cross sections on final states of two $W$ bosons plus four bottom quarks have been measured by the ATLAS Collaboration at the LHC 13 TeV. We reinterpret the experimental data under the scenario of a light charged Higgs boson and find improved agreements. We obtain the first limit from LHC direct searches on the total branching ratio of the three-body decay, $\mathrm{Br}(t\ensuremath{\rightarrow}{H}^{+}b)\ifmmode\times\else\texttimes\fi{}\mathrm{Br}({H}^{+}\ensuremath{\rightarrow}{W}^{+}b\overline{b})$, and the strongest direct constraints on the parameter space of a class of type-I two-Higgs-doublet models.