Simple renormalizable flavor symmetry for neutrino oscillations

TL;DR

The paper introduces a renormalizable flavor symmetry model based on A4 that explains neutrino mixing angles, CP violation, and leptogenesis, fitting current experimental data and making testable predictions for future experiments.

Contribution

It presents a new neutrino mixing model with A4 symmetry and type-I seesaw that accommodates non-zero θ13 and CP violation within a renormalizable framework.

Findings

Normal and inverted hierarchies are compatible within 3σ bounds.

Inverted hierarchy is disfavored by 1σ global analysis, but recent data may favor it.

Predicted effective mass |m_ee| is within reach of upcoming neutrinoless double beta decay experiments.

Abstract

The recent measurement of a non-zero neutrino mixing angle $\theta_{13}$ requires a modification of the tri-bimaximal mixing pattern that predicts a zero value for it. We propose a new neutrino mixing pattern based on a spontaneously-broken $A_{4}$ flavor symmetry and a type-I seesaw mechanism. Our model allows for approximate tri-bimaximal mixing and non-zero $\theta_{13}$, and contains a natural way to implement low and high energy CP violation in neutrino oscillations, and leptogenesis with a renormalizable Lagrangian. Both normal and inverted mass hierarchies are permitted within $3\sigma$ experimental bounds, with the prediction of small (large) deviations from maximality in the atmospheric mixing angle for the normal (inverted) case. Interestingly, we show that the inverted case is excluded by the global analysis in $1\sigma$ experimental bounds, while the most recent MINOS data seem to favor the inverted case. Our model make predictions for the Dirac CP phase in the normal and inverted hierarchies, which can be tested in near-future neutrino oscillation experiments. Our model also predicts the effective mass $|m_{ee}|$ measurable in neutrinoless double beta decay to be in the range $0.04\lesssim |m_{ee}| \lesssim 0.15$ eV for the normal hierarchy and $0.06\lesssim |m_{ee}| \lesssim 0.11$ eV for the inverted hierarchy, both of which are within the sensitivity of the next generation experiments.