Radiative neutrino mass model with degenerate right-handed neutrinos

TL;DR

This paper presents an extension of the radiative neutrino mass model with a U(1) gauge symmetry, enabling degenerate right-handed neutrinos and tiny Yukawa couplings at the TeV scale, linking neutrino masses, dark matter, and leptogenesis.

Contribution

The proposed model extension simultaneously realizes degenerate right-handed neutrinos, tiny Yukawa couplings, and a stable dark matter candidate through TeV scale symmetry breaking.

Findings

Achieves resonant leptogenesis conditions at TeV scale.

Links small scalar couplings to symmetry breaking.

Provides a unified framework connecting neutrino mass, dark matter, and leptogenesis.

Abstract

The radiative neutrino mass model can relate neutrino masses and dark matter at a TeV scale. If we apply this model to thermal leptogenesis, we need to consider resonant leptogenesis at that scale. It requires both finely degenerate masses for the right-handed neutrinos and a tiny neutrino Yukawa coupling. We propose an extension of the model with a U(1) gauge symmetry, in which these conditions are shown to be simultaneously realized through a TeV scale symmetry breaking. Moreover, this extension can bring about a small quartic scalar coupling between the Higgs doublet scalar and an inert doublet scalar which characterizes the radiative neutrino mass generation. It also is the origin of the $Z_2$ symmetry which guarantees the stability of dark matter. Several assumptions which are independently supposed in the original model are closely connected through this extension.