An alternative for righthanded neutrinos: lefthanded see--saw

TL;DR

This paper proposes a novel lefthanded see-saw mechanism where sterile neutrinos are active participants, leading to small active neutrino masses without righthanded neutrinos, and the neutrino mass term is purely Majorana.

Contribution

It introduces a new see-saw model utilizing lefthanded sterile neutrinos, differing from traditional models that rely on righthanded neutrinos.

Findings

Active neutrino masses are small due to the new mechanism.

Heavy passive neutrinos decouple similarly to conventional see-saw.

The neutrino mass term is purely Majorana in this model.

Abstract

A new lefthanded see-saw mechanism is constructed, implying both the smallness of active-neutrino masses and decoupling of heavy passive neutrinos, similarly to the situation in the case of conventional see-saw. But now, in place of the conventional righthanded neutrinos, the lefthanded sterile neutrinos play the role of heavy passive neutrinos, the righthanded neutrinos and righthanded sterile neutrinos being absent. In this case, the neutrino mass term is necessarily of pure Majorana type.