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 tree-level Yukawa couplings to fermions. The other doublet has no vacuum expectation value and no tree-level 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 CP-odd scalar $A$ and the charged scalar $H^\pm$ couple to fermions at one-loop level. We compute the decays of $A$ and $H^\pm$ and in particular the one-loop 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 tree-level 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 13-43