Abstract

We propose a non-minimal left–right symmetric model with parity symmetry where the fermion mixings arise as a result of imposing an mathbf{S}_{3}otimes mathbf{Z}_{2} flavor symmetry, and an extra mathbf{Z}^{e}_{2} symmetry is considered in the lepton sector. Then the neutrino mass matrix possesses approximately the mu –tau symmetry. The breaking of the mu –tau symmetry induces sizable non-zero theta _{13}, and the deviation of theta _{23} from 45^{circ } is strongly controlled by an epsilon free parameter and the neutrino masses. So, an analytic study of the CP parities in the neutrino masses is carried out to constrain the epsilon parameter and the lightest neutrino mass that accommodate the mixing angles. The results are: (a) the normal hierarchy is ruled out for any values of the Majorana phases; (b) for the inverted hierarchy the values of the reactor and atmospheric angles are compatible up to 2, 3~sigma C.L.; (c) the degenerate ordering is the most favorable such that the reactor and atmospheric angle are compatible with the experimental data for a large set of values of the free parameters. The model predicts defined regions for the effective neutrino mass, the neutrino mass scale and the sum of the neutrino masses for the favored cases. Therefore, this model may be testable by the future experiments.

Highlights

  • We know that neutrinos oscillate and have a tiny mass

  • This problem may be alleviated if the minimal extension of the Standard Model (SM) is replaced by the left– right symmetric model (LRSM) [7,11,12,13,14] where the right-handed neutrinos (RHNs) are already included in the matter content

  • We have extended the scalar sector of the LRSM in order to get masses and mixings for fermions

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Summary

Introduction

We know that neutrinos oscillate and have a tiny mass. In the theoretical framework of three active neutrinos, the difference of the squared neutrino masses for a normal (inverted) hierarchy are given by m. We should point out that the RHN mass scale is introduced by hand with no relation whatsoever to the Higgs mechanism, which gives mass to all other fields This problem may be alleviated if the minimal extension of the SM is replaced by the left– right symmetric model (LRSM) [7,11,12,13,14] where the RHNs are already included in the matter content. The highlighted results are: (a) the normal hierarchy is ruled out since the reactor angle comes out being tiny, for any values of the Majorana phases; (b) for the inverted hierarchy there is one combination in the CP parities where the values of the reactor and atmospheric angles are compatible up to 2, 3 σ C.L., but the parameter space is tight; (c) the model favors the degenerate ordering for one combination in the CP parities In this case, the reactor and atmospheric angle are compatible with the experimental data for a large set of values of the free parameters. We present an analytic study of the mixing angles, the results and the predictions in Sect. 5, and we close our discussion with a summary of conclusions

Flavored left–right symmetric model
Masses and mixings
Neutrinos
Charged leptons
PMNS mixing matrix
Analytic study and results
Mixing angles
The effective neutrinoless mass decay
Conclusions

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