Minimal Seesaw Textures with Two Heavy Neutrinos

TL;DR

This paper classifies minimal neutrino mass matrix textures with two heavy neutrinos, identifying patterns compatible with current data and predicting specific outcomes for future experiments.

Contribution

It systematically analyzes and classifies minimal seesaw textures with two heavy neutrinos, including non-diagonal Majorana masses, revealing new viable solutions with testable predictions.

Findings

Seven viable mass matrix patterns match experimental data.

Predictions for the 1-3 mixing angle and neutrinoless double beta decay.

Identification of novel texture forms and potential symmetry links.

Abstract

We systematically analyze the Dirac and the Majorana mass matrices in seesaw models with two heavy right-handed neutrinos. We perform thorough classification of the vanishing matrix elements which are compatible with the results from the current neutrino oscillation experiments. We include the possibility of a non-diagonal Majorana mass matrix which leads to new solutions viable with data. In a basis where the Majorana mass matrix is diagonal, these solutions imply a Dirac matrix with specific relationships amongst its elements. We find that at the level of total 4 zeros together in the Dirac and the Majorana sectors, the mass matrices are almost consistent with the data but one mixing angle is predicted to be unsuitable. At the next level, i.e. with total 3 zeros, only seven patterns of mass matrices describe the experimental data well. The seven solutions have testable predictions for the future neutrino experiments. In particular, each solution has definite predictions about the observation of the 1-3 leptonic mixing angle and the effective mass measured in neutrino-less double beta decay. The solutions of the mass matrices contain novel texture forms and provide new insights into the lepton-generation structure. We also discuss possible connections between these textures and the tri-bimaximal mixing to search for symmetry principles behind the mass matrix structure.