Constraining Type I Seesaw with $A_4$ Flavor Symmetry From Neutrino Data and Leptogenesis

TL;DR

This paper explores a type I seesaw model with $A_4$ flavor symmetry, constraining neutrino parameters and vacuum alignments through leptogenesis, and linking them to observable neutrino data.

Contribution

It introduces a detailed $A_4$ flavor symmetry framework for neutrino masses, constrains model parameters using leptogenesis, and predicts testable ranges for neutrino observables.

Findings

Constraints on $A_4$ vacuum alignments from successful leptogenesis

Predicted ranges for lightest neutrino mass and CP phases

Testable implications for ongoing neutrino experiments

Abstract

We study a type I seesaw model of neutrino masses within the framework of $A_4$ flavor symmetry. Incorporating the presence of both singlet and triplet flavons under $A_4$ symmetry, we construct the leptonic mass matrices involved in type I seesaw mechanism. We then construct the light neutrino mass matrix using the $3\sigma$ values of neutrino oscillation parameters keeping the presently undetermined parameters namely, the lightest neutrino mass $m_{\text{lightest}}$, one Dirac CP phase $\delta$ and two Majorana phases $\alpha, \beta$ as free parameters. Comparing the mass matrices derived using $A_4$ parameters as well as light neutrino parameters, we then evaluate all the $A_4$ parameters in terms of light neutrino parameters. Assuming some specific vacuum alignments of $A_4$ triplet flavon field, we then numerically evaluate all the free parameters in the light neutrino sector, using which we also find out the remaining $A_4$ parameters. We then use the numerical values of these parameters to calculate baryon asymmetry through the mechanism of leptogenesis. We not only constrain the $A_4$ vacuum alignments from the requirement of successful leptogenesis, but also constrain the free parameters in the light neutrino sector $(m_{\text{lightest}}, \delta, \alpha, \beta)$ to certain range of values. These values can be tested in ongoing and future neutrino experiments providing a way to discriminate between different possible $A_4$ vacuum alignments discussed in this work.