Using A4 to Ameliorate Popular Lepton Mixings: A Model for Realistic Neutrino Masses and Mixing Based on Seesaw

Abstract

A neutrino mass model conserving discrete flavour symmetry A4 is proposed. Using an interplay of both Type-I and Type-II seesaw mechanisms the discrepancies present in the popular lepton mixing patterns, viz., Tribimaximal (TBM), Bimaximal (BM), and Golden Ratio (GR) mixings are cured and they were harmonized with the present neutrino oscillation observations. A scenario with no solar mixing (NSM) was also considered. The model has several predictions testable in the light of future oscillation experiments. IntroductionThis talk is based on [1]. A model with two-component Lagrangian formalism based on Type-I and Type-II seesaw mechanism is proposed for tree-level generation of realistic neutrino masses and mixing using the discrete flavour symmetry A4 in [1]. The Type-II seesaw is the dominant contribution, Type-I seesaw is the sub-dominant contribution. Type-II seesaw features vanishing solar splitting ( m 2 solar = 0), θ 13 = 0, θ 23 = π/4 and can have any solar mixing angle. Choices of θ 0 12 corresponding to certain mixing patterns, viz., θ 0 12 = 35.3 • (tribimaximal), 45.0 • (bimaximal), 31.7 • (golden ratio) were considered. Tribimaximal, Bimaximal, Golden Ratio mixing are abbreviated as TBM, BM, and GR mixing, respectively. No solar mixing (NSM), i.e., θ 0 12 = 0 was also studied. Including first-order corrections originating from the sub-dominant Type-I seesaw can yield the values of these oscillation parameters into the ranges allowed by the data leading to interesting interrelationships between them that are testable in future oscillation experiments. For example, normal (inverted) ordering gets associated with first (second) octant of θ 23 . The 3σ neutrino oscillation parameters global fits [2, 3]: