Doubly charged scalar decays in a type II seesaw scenario with two Higgs triplets

Abstract

The type II seesaw mechanism for neutrino mass generation usually makes use of one complex scalar triplet. The collider signature of the doubly-charged scalar, the most striking feature of this scenario, consists mostly in decays into same-sign dileptons or same-sign W boson pairs. However, certain scenarios of neutrino mass generation, such as those imposing texture zeros by a symmetry mechanism, require at least two triplets in order to be consistent with the type II seesaw mechanism. We develop a model with two such complex triplets and show that, in such a case, mixing between the triplets can cause the heavier doubly-charged scalar mass eigenstate to decay into a singly-charged scalar and a W boson of the same sign. Considering a large number of benchmark points with different orders of magnitude of the ∆L = 2 Yukawa couplings, chosen in agreement with the observed neutrino mass and mixing pattern, we demonstrate that H ++ 1 → H + 2 W + can have more than 99% branching fraction in the cases where the vacuum expectation values of the triplets are small. It is also shown that the above decay allows one to differentiate a two-triplet case at the LHC, through the ratios of events in various multi-lepton channels.

CP-violating phase in a two Higgs triplet scenario: Some phenomenological implications

“…An important conclusion of this study was that, whereas the doubly charged scalar in the single triplet scenario would decay mostly in the ± ± or W ± W ± modes, the decay channel H ++ 1 −→ H + 2 W + acquires primacy over a large region of the parameter space. Some predictions on this in the context of the Large Hadron Collider were also shown in reference [3]. However, an added possibility with two triplet is the possibility of at least one CP-violating phase being there.…”

“…It is interesting to note that if we drop those quartic terms for simplification from our scalar potential, then our doubly charged mass matrix remains the same as in [3]. This gives the impression that the relative phase between triplets does not affect the doubly charged mass matrix if we drop the quartic terms in the potential.…”

“…In [3], all the vev's as well the parameters in the potential were assumed to be real. As has already ben mentioned, this need not be the situation in general.…”

“…This resurrects the relevance of the phenomenology of two-triplet, one doublet scalar sectors, this time with practical implications. We have studied such phenomenology in reference [3]. An important conclusion of this study was that, whereas the doubly charged scalar in the single triplet scenario would decay mostly in the ± ± or W ± W ± modes, the decay channel H ++ 1 −→ H + 2 W + acquires primacy over a large region of the parameter space.…”

“…First of all, as a result of mixing between two triplets and presence of a relative phase between them, something on which no phenomenological restrictions exits, the heavier doubly charged scalar can now decay frequently into the lighter doubly charged scalar plus the SM-like Higgs boson, i. + mostly dominates, and its consequence was discussed in some detail in our earlier work [3] on the CP-conserving scenario.…”