Light neutrinos from massless texture and below TeV seesaw scale

TL;DR

This paper explores conditions under which a type-I seesaw mechanism can produce exactly massless neutrinos at tree level, with potential for small observed masses via higher order corrections, even at low energy scales.

Contribution

It identifies specific conditions and symmetries allowing three massless neutrinos in a low-scale seesaw model, expanding understanding of neutrino mass generation.

Findings

Conditions for massless neutrinos at tree level are established.

Examples relate these conditions to an underlying U(1) symmetry.

Higher order corrections can generate small neutrino masses at low scales.

Abstract

We present general conditions on Dirac and Majorana mass terms under which a type-I seesaw mechanism can lead to three exactly massless neutrinos at the tree level. We depict several examples where the conditions are satisfied and relate some of them to an underlying U(1) symmetry. We show that higher order corrections may generate the small observed masses and this may be achieved even when the heavy Majorana neutrinos are at the electroweak scale or a little higher.