Horizontal Gauge Symmetry and Masses of Neutrinos

Abstract:The only possible doubly-charged scalar decays into two Standard Model particles are into pairs of same-sign charged leptons, H ±± → l ± l ± , l = e, µ, τ , or gauge bosons, H ±± → W ± W ± ; being necessary the observation of both to assert the violation of lepton number. However, present ATLAS and CMS limits on doubly-charged scalar production are obtained under specific assumptions on its branching fractions into dileptons only. Although they can be extended to include decays into dibosons and lepton number violating processes. Moreover, the production rates also depend on the type of electroweak multiplet H ±± belongs to. We classify the possible alternatives and provide the Feynman rules and codes for generating the corresponding signals for pair and associated doubly-charged scalar production, including the leading contribution from the s-channel exchange of electroweak gauge bosons as well as the vector-boson fusion corrections. Then, using the same analysis criteria as the LHC collaborations we estimate the limits on the H ±± mass as a function of the electroweak multiplet it belongs to, and obtain the bounds on the lepton number violating processes pp → H ±± H ∓∓ → ± ± W ∓ W ∓ and pp → H ±± H ∓ → ± ± W ∓ Z, = e, µ, implied by the ATLAS and CMS doubly-charged scalar searches.

Section: Introductionmentioning

confidence: 99%

LHC bounds on lepton number violation mediated by doubly and singly-charged scalars

Águila

Chala

2014

“…To discuss this point, let us investigate the neutrino mass terms. The masses of light neutrinos in our model are given by the ordinary seesaw relation [107][108][109][110][111][112],…”

Section: Jhep02(2016)120mentioning

confidence: 99%

The ATLAS diboson resonance in non-supersymmetric SO(10)

Evans

Olive

Zheng

2016

SO(10) grand unification accommodates intermediate gauge symmetries with which gauge coupling unification can be realized without supersymmetry. In this paper, we discuss the possibility that a new massive gauge boson associated with an intermediate gauge symmetry explains the excess observed in the diboson resonance search recently reported by the ATLAS experiment. The model we find has two intermediate symmetries,where the latter gauge group is broken at the TeV scale. This model achieves gauge coupling unification with a unification scale sufficiently high to avoid proton decay. In addition, this model provides a good dark matter candidates, whose stability is guaranteed by a Z 2 symmetry present after the spontaneous breaking of the intermediate gauge symmetries. We also discuss prospects for testing these models in the forthcoming LHC experiments and dark matter detection experiments.

“…To take a simple example, consider the totally antisymmetric rank-four tensor multiplet of SU (4). This is a singlet, and thus trivially anomaly free.…”

Section: Introductionmentioning

confidence: 99%

Families from supergroups and predictions for leptonic CP violation

Barr

Chen

2017

As was shown in 1984 by Caneschi, Farrar, and Schwimmer, decomposing representations of the supergroup SU(M |N ), can give interesting anomaly-free sets of fermion representations of SU(M ) × SU(N ) × U(1). It is shown here that such groups can be used to construct realistic grand unified models with non-abelian gauged family symmetries. A particularly simple three-family example based on SU(5) × SU(2) × U(1) is studied. The forms of the mass matrices, including that of the right-handed neutrinos, are determined in terms of SU(2) Clebsch coefficients; and the model is able to fit the lepton sector and predict the Dirac CP-violating phase of the neutrinos. Models of this type would have a rich phenomenology if part of the family symmetry is broken near the electroweak scale.