Option of three pseudo--Dirac neutrinos

TL;DR

This paper explores a pseudo-Dirac neutrino model as an alternative to the see-saw mechanism, explaining neutrino oscillation phenomena and suggesting a specific neutrino mass matrix structure.

Contribution

It introduces a novel pseudo-Dirac neutrino framework with a specific mass matrix form, providing a consistent explanation for various neutrino oscillation observations.

Findings

Neutrino oscillations explain solar and atmospheric neutrino deficits.

The model accommodates LSND results with adjustable parameters.

Atmospheric neutrinos mainly oscillate into tau neutrinos.

Abstract

As an alternative for popular see-saw mechanism, the option of three pseudo% -Dirac neutrinos is discussed, where ${1/2}(m^{(L)} + m^{(R)}) \ll m^{(D)}$ for their Majorana and Dirac masses. The actual neutrino mass matrix is assumed in the form of tensor product $ M^{(\nu)} \otimes {(\{array} {cc} \lambda^{(L)} & 1 1 & \lambda^{(R)} \{array})}$, where $ M^{(\nu)}$ is a neutrino family mass matrix ($ M^{(\nu) \dagger} = M^{(\nu)}$) and $\lambda^{(L,R)} \equiv m^{(L,R)}/m^{(D)}$ with $ m^{(L)}$, $ m^{(R)}$ and $ m^{(D)} $ being taken as universal for three neutrino families. It is shown that three neutrino effects (deficits of solar $\nu_e $'s and atmospheric $ \nu_\mu $'s as well as the possible LSND excess of $\nu_e $'s in accelerator $\nu_\mu $ beam) can be nicely described by the corresponding neutrino oscillations, though the LSND effect may, alternatively, be eliminated (by a parameter choice). Atmospheric $\nu_\mu $'s oscillate dominantly into $\nu_\tau $'s, while solar $\nu_e $'s - into (existing here automatically) Majorana sterile counterparts of $\nu_e $'s. A phenomenological texture for neutrinos, compatible with the proposed description, is briefly presented.