
Rikard Enberg, Johan Rathsman, Glenn Wouda
Higgs phenomenology in the Stealth Doublet Model
Abstract
We analyze a model for the Higgs sector with two scalar doublets and a softly broken $Z_2$ symmetry. One of the doublets breaks the electroweak symmetry and has treelevel Yukawa couplings to fermions. The other doublet has no vacuum expectation value and no treelevel couplings to fermions. Because 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 CPodd scalar $A$ and the charged scalar $H^\pm$ couple to fermions at oneloop level. We compute the decays of $A$ and $H^\pm$ and in particular the oneloop decays $A \to f \bar{f}$, $H^\pm \to f \bar{f}^\prime $, $H^\pm \to W^\pm Z $ and $H^\pm \to W^\pm \gamma$. We also describe how to calculate and renormalize such processes in our model. We find that if one of $H^\pm$ or $A$ is the lightest scalar, $H^\pm \to W^\pm \gamma$ or $ A \to b \bar{b} $ are typically their respective dominating decay channels. Otherwise, the dominating decays of $H^\pm$ and $A$ are into a scalar and a vector. Due to the absence of treelevel fermion couplings for $H^\pm$ 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 $H^\pm \to W^\pm \gamma$ is realized in Nature, we estimate that there should be a considerable amount of such events in the present LHC data.
LU TP 1343
