Schizophrenic Neutrinos and $\nu$-less Double Beta Decay

TL;DR

This paper proposes a novel neutrino model where neutrinos can be partly Dirac and partly Majorana, linking neutrino properties to cosmological phenomena and predicting larger lower limits for neutrinoless double beta decay in inverted hierarchy.

Contribution

It introduces a new neutrino mass model with mixed Dirac and Majorana characteristics using an $S_3$ symmetry, connecting neutrino physics with cosmology.

Findings

Inverted hierarchy predicts higher lower limits for neutrinoless double beta decay.

Tri-bi-maximal mixing is achieved at leading order.

The model is compatible with supersymmetric see-saw frameworks.

Abstract

We point out a novel possibility for neutrinos where all neutrino flavors can be part Dirac and part Majorana. Our primary motivation for this model comes from an attempt to use supersymmetric see-saw models to tie inflation, baryon asymmetry of the Universe and dark matter to the neutrino sector. The idea however could stand on its own, with or without supersymmetry. We present a realization of this possibility within an $S_3$ family symmetry for neutrino masses, where we obtain tri-bi-maximal mixing for neutrinos to the leading order. The model predicts that for the case of inverted hierarchy, the lower limit on the neutrino mass measured in neutrinoless double beta decay experiments is about a factor of two larger than the usual case.