The $W\gamma$ decay of the elusive charged Higgs boson in the two-Higgs-doublet model with vectorlike fermions

Abstract

The LHC search for the charged Higgs boson in the intermediate-mass range ($M_{H^{\pm }}\sim m_t$) is actively being performed after the next-to-leading order calculation of the total production cross section of $pp\to H^{\pm }{W}^{\mp }b\bar{b}$. In the decay part, only the $\tau \nu$ mode is mainly concerned because of the experimental difficulty in the $tb$ mode. In the framework of a two-Higgs-doublet model, we suggest that the $W\gamma$ channel can be helpful in probing this charged Higgs boson, if introducing vectorlike fermions. In type-I-II model where the SM fermions are assigned in type-I while the vectorlike fermions are in type-II, the branching ratio is greatly enhanced up to $\sim \mathcal{O}(0.01)$ in a large portion of the parameter space allowed by the Higgs precision data, the electroweak oblique parameters, and the direct search bounds at the LHC. Two kinds of production channels, $gg\to H^{\pm }{W}^{\mp }b\bar{b}$ and $gg\to H/A\to H^{\pm }{W}^{\mp }$, are also studied. We find that the signal rate $\sigma \times \mathcal{B}(W\gamma )$ is quite sizable, more than 10 fb in some parameter space.

Comments: The study is extended in the whole intermediate mass range of the charged Higgs boson. 35 pages, 14 figures, To appear in PRD