Dark-matter sterile neutrinos in models with a gauge singlet in the Higgs sector

TL;DR

This paper explores a model where sterile neutrinos as dark matter are produced via an extended Higgs sector, affecting their relic abundance, free-streaming length, and implications for cosmology and collider experiments.

Contribution

It introduces a novel model with a gauge-singlet Higgs that generates sterile neutrino masses, altering their production and observational constraints.

Findings

Relic abundance independent of mixing angles

Reduced free-streaming length compared to traditional warm dark matter

Implications for electroweak phase transition and collider experiments

Abstract

Sterile neutrino with mass of several keV can be the cosmological dark matter, can explain the observed velocities of pulsars, and can play an important role in the formation of the first stars. We describe the production of sterile neutrinos in a model with an extended Higgs sector, in which the Majorana mass term is generated by the vacuum expectation value of a gauge-singlet Higgs boson. In this model the relic abundance of sterile neutrinos does not necessarily depend on their mixing angles, the free-streaming length can be much smaller than in the case of warm dark matter produced by neutrino oscillations, and, therefore, some of the previously quoted bounds do not apply. The presence of the gauge singlet in the Higgs sector has important implications for the electroweak phase transition, baryogenesis, and the upcoming experiments at the Large Hadron Collider and a Linear Collider.