Survey of Texture Zeros with Light Dirac Neutrinos

TL;DR

This paper systematically classifies all possible texture zeros in the light neutrino mass matrix considering Dirac neutrinos, revealing which textures are compatible with current data and their implications for neutrino parameters.

Contribution

It provides a comprehensive classification of texture zeros for Dirac neutrinos, including non-Hermitian cases, and analyzes their compatibility with experimental constraints.

Findings

Hermitian textures are all disallowed by data.

Some non-Hermitian textures with four zeros are allowed.

Allowed textures show correlations with neutrino mass ordering and cosmological bounds.

Abstract

We classify all possible texture zeros in light neutrino mass matrix in diagonal charged lepton basis by considering Dirac nature of light neutrinos. For Hermitian nature of neutrino mass matrix, the number of possible texture zeros remain same as Majorana texture zeros, but with less free parameters due to the absence of additional Majorana CP phases. Relaxing the Hermitian nature of neutrino mass matrix lead to many more possibilities and freedom due to additional CP phases, mixing angles not constrained by neutrino data. While we find that none of the texture zeros in Hermitian case are allowed, in non-Hermitian case some textures even with four zeros are allowed. While most of the one-zero, two-zero and three-zero textures in this case are allowed, four-zero textures are tightly constrained with only 6 allowed out of 126 possibilities. The allowed textures also give interesting correlations between light neutrino parameters with sharp distinctions between normal and inverted mass ordering. Many of these allowed textures also saturate the Planck 2018 upper bound on the sum of absolute neutrino masses.