Light sterile neutrino and dark matter in left-right symmetric models without a Higgs bidoublet

Abstract

We present a class of left-right symmetric models where Dirac as well as Majorana mass terms of neutrinos can arise at one-loop level in a scotogenic fashion: with dark matter particles going inside the loop. We show the possibility of naturally light right handed neutrinos that can have interesting implications at neutrinoless double beta decay experiments as well as cosmology. Apart from a stable dark matter candidate stabilised by a remnant Z 2 symmetry, one can also have a long lived keV sterile neutrino dark matter in these models. This class of models can have very different collider signatures compared to the conventional left-right models.

Compatibility of $$A_{4}$$ A 4 flavour symmetric minimal extended seesaw with $$(3+1)$$ ( 3

“…We first single out the disallowed textures based on the known results from previous analysis [51][52][53][59][60][61][62]. They are given as follows.…”

“…While the usual seesaw mechanisms like type I [28][29][30][31][32], type II [33][34][35][36][37][38][39] and type III [40] explaining the lightness of active neutrinos were studied in details for a long time, their extensions to the 3+1 case was not very straightforward primarily due to the gauge singlet nature of the sterile neutrino. Yet, there have been several proposals to generate a 4 × 4 light neutrino mass matrix within different seesaw frameworks in recent times [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. Here we adopt a minimal framework known as the minimal extended seesaw proposed in the 3 + 1 neutrino context by [42,43] and study different possible realisations within the framework of non-abelian discrete flavour symmetry A 4 .…”

Phenomenological study of texture zeros in lepton mass matrices of minimal left-right symmetric model

“…The SU (2) R triplet scalar masses are allowed to be even smaller than the heaviest right-handed neutrino mass. Right-handed neutrinos could nevertheless be indirectly constrained by neutrinoless double-beta decays and cosmology [114][115][116].…”

Observable lepton number violation with predominantly Dirac nature of active neutrinos

“…Very recently this model was also studied in the context of 750 GeV diphoton excess at LHC [62][63][64] 1 by several authors [67][68][69][70]. As shown recently [71], the heavy fermions introduced to generate light neutrino masses can have some non-trivial transformations under additional discrete symmetries such that, a tiny Dirac neutrino mass can be generated at one-loop level through scotogenic fashion [72]. The scalar fields of SU(2) L and SU(2) R sectors do not necessarily have the same transformations under the additional discrete symmetries thereby deviating from the purely left-right symmetric limit of the conventional LRSM.…”

“…In the fermion content shown in table 1, the doublets are the usual LRSM fermion doublets and the vector like fermions U, D, E are required for the universal seesaw for charged fermion masses. The gauge singlet fermions ν R , ψ are chosen to generate neutrino masses at one loop order, similar to the way it was shown in [71] within LRSM and more recently in [135]. Their …”