Neutrino mass hierarchy and the origin of leptonic flavor mixing from the right-handed sector

TL;DR

This paper proposes a neutrino mass model where leptonic mixing arises from a heavy Majorana sector via the seesaw mechanism, favoring a normal hierarchy and predicting small lightest neutrino mass with implications for neutrinoless double beta decay.

Contribution

It introduces a model with diagonal Dirac mass matrices and a heavy Majorana sector, explaining leptonic mixing and neutrino mass hierarchy within grand unified theories.

Findings

Normal neutrino mass hierarchy is preferred.

Lightest neutrino mass is typically small.

Neutrinoless double beta decay rates are predicted to be unobservable.

Abstract

We consider a neutrino mass model where all leptonic mixing is induced by a heavy Majorana sector through the seesaw type I mechanism, while the Dirac mass matrices are diagonal. Such a pattern occurs naturally in grand unified theories. Constraints on the parameters of the models are considered and it is shown that a normal neutrino mass hierarchy is preferred. The lightest neutrino mass is typically small, leading to nonobservable rates for neutrinoless double beta decay in the normal hierarchy case.