Non-zero θ13 and δCP phase with A4 flavor symmetry and deviations to tri-bi-maximal mixing via Z2 × Z2 invariant perturbations in the neutrino sector

Abstract

In this work, a flavour theory of a neutrino mass model based on A4 symmetry is considered to explain the phenomenology of neutrino mixing. The spontaneous symmetry breaking of A4 symmetry in this model leads to tribimaximal mixing in the neutrino sector at a leading order. We consider the effect of Z2×Z2 invariant perturbations in neutrino sector and find the allowed region of correction terms in the perturbation matrix that is consistent with 3σ ranges of the experimental values of the mixing angles. We study the entanglement of this formalism on the other phenomenological observables, such as δCP phase, the neutrino oscillation probability P(νμ→νe), the effective Majorana mass |mee| and |mνeeff|. A Z2×Z2 invariant perturbations in this model is introduced in the neutrino sector which leads to testable predictions of θ13 and CP violation. By changing the magnitudes of perturbations in neutrino sector, one can generate viable values of δCP and neutrino oscillation parameters. Next we investigate the feasibility of charged lepton flavour violation in type-I seesaw models with leptonic flavour symmetries at high energy that leads to tribimaximal neutrino mixing. We consider an effective theory with an A4×Z2×Z2 symmetry, which after spontaneous symmetry breaking at high scale which is much higher than the electroweak scale leads to charged lepton flavour violation processes once the heavy Majorana neutrino mass degeneracy is lifted either by renormalisation group effects or by a soft breaking of the A4 symmetry. In this context the implications for charged lepton flavour violation processes like μ→eγ, τ→eγ, τ→μγ are discussed.