Tri-bimaximal Neutrino Mixing from A(4) and \theta_{13} \sim \theta_C

TL;DR

This paper presents a Seesaw A(4) model that naturally explains a relatively large reactor angle _{13}  _C, consistent with experimental data, while maintaining the Tri-bimaximal mixing pattern for _{12}.

Contribution

It introduces a novel Seesaw A(4) model that allows _{13}  _C without conflicting with TBM predictions, evading previous assumptions.

Findings

_{13}  _C is achievable in the model.

The model predicts a sum-rule for _{23} deviation.

The model aligns with current experimental data.

Abstract

It is a common believe that, if the Tri-bimaximal mixing (TBM) pattern is explained by vacuum alignment in an A(4) model, only a very small reactor angle, say \theta_{13} \sim \lambda^2_C being \lambda_C \equiv \theta_C the Cabibbo angle, can be accommodated. This statement is based on the assumption that all the flavon fields acquire VEVs at a very similar scale and the departures from exact TBM arise at the same perturbation level. From the experimental point of view, however, a relatively large value \theta_{13} \sim \lambda_C is not yet excluded by present data. In this paper, we propose a Seesaw A(4) model in which the previous assumption can naturally be evaded. The aim is to describe a \theta_{13} \sim \lambda_C without conflicting with the TBM prediction for \theta_{12} which is rather close to the observed value (at \lambda^2_C level). In our model the deviation of the atmospherical angle from maximal is subject to the sum-rule: \sin ^2 \theta_{23} \approx 1/2 + \sqrt{2}/2 \sin \delta \cos \theta_{13} which is a next-to-leading order prediction of our model.