W γ decay of the elusive charged Higgs boson in the two-Higgs-doublet model with vectorlike fermions

The LHC search for the charged Higgs boson in the intermediate-mass range (MH±∼mt) is actively being performed after the next-to-leading order calculation of the total production cross section of pp→H±W∓bb¯. In the decay part, only the τν 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 Wγ channel can be helpful in probing this charged Higgs boson, if introducing vectorlike fermions. In the type-I-II model where the standard model fermions are assigned in type-I while the vectorlike fermions are in type-II, the branching ratio is greatly enhanced up to ∼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→H±W∓bb¯ and gg→H/A→H±W∓, are also studied. We find that the signal rate σ×B(Wγ) is quite sizable, more than 10 fb in some parameter space.