Neutrino Mixing: $A_4$ Variations

TL;DR

This paper discusses the shift from tribimaximal to cobimaximal neutrino mixing within the $A_4$ symmetry framework, proposing three realistic models that align with current experimental data.

Contribution

It introduces three specific models under $A_4$ symmetry that realize cobimaximal mixing, improving upon previous tribimaximal models.

Findings

Models successfully reproduce current neutrino mixing angles.

Two models with three parameters, one with two, fit experimental data.

Supports cobimaximal mixing as a viable neutrino mixing pattern.

Abstract

In the context of the non-Abelian discrete symmetry $A_4$, the neutrino mass matrix has been studied extensively. A brief update is presented to focus on the conceptual shift from tribimaximal mixing ($\theta_{13} = 0$, $\theta_{23} = \pi/4$, $\tan^2 \theta_{12} = 1/2$) to $\underline{\rm cobimaximal}$ mixing ($\theta_{13} \neq 0$, $\theta_{23} = \pi/4$, $\delta_{CP} = \pm \pi/2$) which agrees well with present data. Three specific realistic examples are proposed, two with three and the third with just two parameters.