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.
We consider a scenario where, along with the usual Higgs doublet, two scalar triplets are present. The extension of the triplet sector is required for the Type II mechanism for the generation of neutrino masses, if this mechanism has to generate a neutrino mass matrix with two-zero texture. One CP-violating phase has been retained in the scalar potential of the model, and all parameters have been chosen consistently with the observed neutrino mass and mixing patterns. We find that a large phase ( 60 • ) splits the two doubly-charged scalar mass eigenstates wider apart, so that the decay H ++ 1
The type III seesaw mechanism for neutrino mass generation usually makes use of at least two Y = 0, SU (2) L lepton triplets. We augment such a model with a third triplet and a sterile neutrino, both of which are odd under a conserved Z 2 symmetry. With all new physics confined to the Z 2 -odd sector, whose low energy manifestation is in some higher-dimensional operators, a fermionic dark matter candidate is found to emerge. We identify the region of the parameter space of the scenario, which is consistent with all constraints from relic density and direct searches, and allows a wide range of masses for the dark matter candidate.
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