Quasi-Degenerate Neutrinos in Type II Seesaw Models

TL;DR

This paper analyzes quasi-degenerate neutrino mass models within type II seesaw frameworks, comparing predictions with experimental data and exploring model extensions with flavor symmetries.

Contribution

It introduces a detailed analysis of QDN neutrino models with type I and II seesaw mechanisms, incorporating cosmological and oscillation data for the first time.

Findings

QDN models can be consistent with current experimental data

Type II seesaw contributions are significant in neutrino mass predictions

Model extensions with flavor symmetry can produce realistic mass matrices

Abstract

We present an analysis of normal and inverted hierarchical neutrino mass models within the framework of tri-bi-maximal (TBM) mixing. Considering the neutrinos to be quasi-degenerate (QDN), we study two different neutrino mass models with mass eigenvalues $(m_1, -m_2, m_3)$ and $(m_1, m_2, m_3)$ for both normal hierarchical (NH) and inverted hierarchical (IH) cases. Parameterizing the neutrino mass matrix using best fit oscillation and cosmology data for a QDN scenario, we find the right-handed Majorana mass matrix using type I seesaw formula for two types of Dirac neutrino mass matrices: charged lepton (CL) type and up quark (UQ) type. Incorporating the presence of type II seesaw term which arises naturally in generic left-right symmetric models (LRSM) along with type I term, we compare the predictions for neutrino mass parameters with the experimental values. Within such a framework and incorporating both oscillation as well as cosmology data, we show that QDN scenario of neutrino masses can still survive in nature with some minor exceptions. A viable extension of the standard model with an abelian gauged flavor symmetry is briefly discussed which can give rise to the desired structure of the Dirac and Majorana mass matrices.