Light Charged Higgs Bosons to AW/HW via Top Decay

TL;DR

This paper explores the potential of detecting light charged Higgs bosons via exotic decay channels in top quark decays at the 14 TeV LHC, providing new bounds and discovery prospects in the Type II 2HDM.

Contribution

It introduces a detailed collider analysis for the exotic decay channel $H^ ightarrow AW/HW$, expanding search strategies beyond conventional methods.

Findings

Exclusion limits on ${\rm BR}(t \rightarrow H^+ b)$ are about 0.2% (single top) and 0.03% (top pair) at 300 fb$^{-1}$.

Discovery is feasible at large and small $\tan\beta$ values within certain mass ranges.

Exotic decay channels complement traditional $H^\pm \rightarrow \tau\nu$ searches.

Abstract

While current ATLAS and CMS measurements exclude a light charged Higgs ($m_{H^\pm}<160$ GeV) for most of the parameter region in the context of the MSSM scenarios, these bounds are significantly weakened in the Type II 2HDM once the exotic decay channel into a lighter neutral Higgs, $H^\pm \to AW/HW$, is open. In this study, we examine the possibility of a light charged Higgs produced in top decay via single top or top pair production, with the subsequent decay $H^\pm \rightarrow AW/HW$, which can reach a sizable branching fraction at low $\tan\beta$ once it is kinematically permitted. With a detailed collider analysis, we obtain exclusion and discovery bounds for the 14 TeV LHC assuming the existence of a 70 GeV neutral scalar. Assuming ${\rm BR}(H^\pm \rightarrow AW/HW)=100\%$ and ${\rm BR}(A/H \rightarrow \tau\tau)=8.6\%$, the 95% exclusion limits on ${\rm BR}(t \rightarrow H^+ b)$ are about 0.2% and 0.03% for single top and top pair production respectively, with an integrated luminosity of 300 ${\rm fb}^{-1}$. The discovery reaches are about 3 times higher. In the context of the Type II 2HDM, discovery is possible at both large $\tan\beta > 17$ for 155 GeV $< m_{H^\pm} <$ 165 GeV, and small $\tan\beta < 6$ over the entire mass range. Exclusion is possible in the entire $\tan\beta$ versus $m_{H^\pm}$ plane except for charged Higgs masses close to the top threshold. The exotic decay channel $H^\pm \to AW/HW$ is therefore complementary to the conventional $H^\pm \rightarrow \tau\nu$ channel.