Higgs phenomenology in the stealth doublet model

We analyze a model for the Higgs sector with two scalar doublets and a Z(2) symmetry that is manifest in the Yukawa sector but broken in the potential. Thus, one of the doublets breaks the electroweak symmetry and has tree-level Yukawa couplings to fermions, whereas the other doublet has no vacuum expectation value and no tree-level couplings to fermions. Since the Z(2) parity is broken the two doublets can mix, which leads to a distinct and novel phenomenology. This stealth doublet model can be seen as a generalization of the inert doublet model with a broken Z(2) symmetry. We outline the model and present constraints from theory, electroweak precision tests, and collider searches, including the recent observation of a Higgs boson at the LHC. The charged scalar H-+/- and the CP-odd scalar A couple to fermions at one-loop level. We compute the decays of H-perpendicular to and A and in particular the one-loop decays A -> f (f) over bar, H-perpendicular to -> f (f) over bar', H-+/- -> W-+/- Z and H-+/- -> W-+/-gamma. We also describe how to calculate and renormalize such processes in our model. We find that if one of H-+/- or A is the lightest scalar, H-+/- -> W-+/-gamma or A -> b (b) over bar are typically their respective dominating decay channels. Otherwise, the dominating decays of H-+/- and A are into a scalar and a vector. Due to the absence of tree-level fermion couplings for H-+/- and A, we consider pair production and associated production with vector bosons and scalars at the LHC. If the parameter space of the model that favors H-+/- -> W-+/-gamma. is realized in Nature, we estimate that there could be a considerable amount of such events in the present LHC data. (Less)