Some consequences of a Higgs triplet

Abstract

We consider an extension of the scalar sector of the Standard Model with a single complex Higgs triplet X. Such extensions are the most economic, model-independent way of generating neutrino masses through triplet interactions. We show that a term like a₀ΦΦX† must be included in the most general potential of such a scenario in order to avoid a massless neutral physical scalar. We also demonstrate that a₀ must be real, thus ruling out any additional source of CP violation. We then examine the implications of this term in the mass matrices of the singly and doubly charged scalar, neutral scalar and pseudoscalar fields. We find that, for small values of a₀/v₂, where v₂ is the triplet vev, the spectrum allows the decay of heavier scalars into lighter ones via gauge interactions. For large a₀/v₂, the doubly charged, singly charged and neutral pseudoscalar bosons become practically degenerate, while the even-parity neutral scalars remain considerably lighter, thus emphasizing the possibility of decay of the singly charged or neutral pseudoscalar states into the neutral scalars. Constraints from the ρ-parameter are used to find nontrivial limits on the charged Higgs mass depending on a₀. We also study the couplings of the various physical states in this scenario. For small values of |a₀|/v₂, we find the lightest neutral scalar field to be triplet dominated, and thus having extremely suppressed interactions with fermion as well as gauge–boson pairs.