Deviations from Tri-Bimaximal Neutrino Mixing Using Type II Seesaw

TL;DR

This paper explores how deviations from tri-bimaximal neutrino mixing, caused by type II seesaw contributions, can explain the non-zero reactor angle, fitting data within flavor symmetry models and analyzing parameter predictions.

Contribution

It introduces a minimal type II seesaw structure to generate deviations from TBM mixing, aligning theoretical predictions with experimental data.

Findings

Type II seesaw induces necessary deviations from TBM.

Predictions for neutrino parameters fit within 3σ experimental range.

Two flavor symmetry models justify the minimal structure used.

Abstract

We study the possibility of generating deviations from tri-bimaximal (TBM) neutrino mixing to explain the non-zero reactor mixing angle within the framework of both type I and type II seesaw mechanisms. The type I seesaw term gives rise to the $\mu-\tau$ symmetric TBM pattern of neutrino mass matrix as predicted by generic flavor symmetry models like $A_4$ whereas the type II seesaw term gives rise to the required deviations from TBM pattern to explain the non-zero $\theta_{13}$. Considering extremal values of Majorana CP phases such that the neutrino mass eigenvalues have the structure $(m_1, -m_2, m_3)$ and $(m_1, m_2, m_3)$, we numerically fit the type I seesaw term by taking oscillation as well as cosmology data and then compute the predictions for neutrino parameters after the type II seesaw term is introduced. We consider a minimal structure of the type II seesaw term and check whether the predictions for neutrino parameters lie in the $3\sigma$ range. We also outline two possible flavor symmetry models to justify the minimal structure of the type II seesaw term considered in the analysis.