Degenerate neutrino mass models revisited

TL;DR

This paper introduces a parametrisation for degenerate neutrino mass models with $$ symmetry, allowing detailed numerical analysis and compatibility with experimental data, including oscillation and cosmological bounds.

Contribution

The paper presents a new parametrisation for degenerate neutrino mass models that can adjust the solar mixing angle while satisfying experimental constraints.

Findings

The parametrisation can lower the solar mixing angle below tri-bimaximal value.

Models maintain maximal atmospheric mixing and zero reactor angle.

Constraints from oscillation, $0 uetaeta$, and cosmology are considered.

Abstract

A parametrisation of the degenerate neutrino mass matrix obeying $\mu -\tau$ symmetry, is introduced for detailed numerical analysis. As a continuation of our earlier work on normal and inverted hierarchical models, the present parametrisation for degenerate models has the ability to lower the solar mixing angle below the tri-bimaximal value $\tan^{2}\theta_{12}=0.5$, while maintaining the condition of maximal atmospheric mixing angle and zero reactor angle. The combined data on the mass-squared differences derived from various oscillation experiments, and also from the bounds on absolute neutrino masses in $0\nu\beta\beta$ decay and cosmology, gives certain constraints on the validity of the degenerate models.