Abstract
Motivated by the recent resurrection of the evidence for an eV scale sterile neutrino from the MiniBooNE experiment, we revisit one of the most minimal seesaw model known as the minimal extended seesaw that gives rise to a 3+1 light neutrino mass matrix. We consider the presence of A_{4} flavour symmetry which plays a non-trivial role in generating the structure of the neutrino mass matrix. Considering a diagonal charged lepton mass matrix and generic vacuum alignments of A_{4} triplet flavons, we classify the resulting mass matrices based on their textures. Keeping aside the disallowed texture zeros based on earlier studies of 3+1 neutrino textures, we categorise the remaining ones based on texture zeros, mu –tau symmetry in the 3times 3 block and hybrid textures. After pointing out the origin of such 3+1 neutrino textures to A_{4} vacuum alignments, we use the latest 3+1 neutrino oscillation data and numerically analyse the texture zeros and mu –tau symmetric cases. We find that a few of them are allowed from each category predicting interesting correlations between neutrino parameters. We also find that all of these allowed cases prefer normal hierarchical pattern of light neutrino masses over inverted hierarchy.
Highlights
Bay [11] and RENO [12]
Adopting the classifications of different textures in 4×4 mass matrix not ruled out from previous studies and the method of numerical analysis discussed in the previous section we have analysed all possible mass matrices either with texture zeros or with μ–τ symmetry in the 3×3 block
Out of four different classes belonging to this type of texture we found three of them to be allowed for normal hierarchy (NH) of active neutrino masses
Summary
Apart from the currently unknown issues in the neutrino sector, like mass hierarchy, Dirac CP violating phase as the global fit data suggest [13], another interesting question in the neutrino sector is the possibility of additional neutrino species with eV scale mass This has turned out to be not just a speculation, but has gathered considerable attention in the last two decades following some anomalies reported by a few experiments. In the original proposal [43] the A4 flavour symmetry was utilised but within the limited discussion the issue of non-zero reactor mixing angle as well as different A4 vacuum alignments were not addressed In another recent work based on the same model with A4 flavour symmetry [56], some details of the associated neutrino phenomenology was discussed by sticking to the effective 3 × 3 active neutrino mass matrix which can be generated by integrating out the sterile neutrino.
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