keV sterile neutrino dark matter in gauge extensions of the standard model

TL;DR

This paper explores how gauge extensions of the standard model can produce keV sterile neutrinos as warm dark matter, using out-of-equilibrium decays to prevent overproduction and match observed dark matter density.

Contribution

It demonstrates a mechanism within gauge extensions to generate keV sterile neutrino dark matter by utilizing out-of-equilibrium decays for density dilution.

Findings

Out-of-equilibrium decay can dilute sterile neutrino density

Universal conditions for gauge extensions to produce dark matter

Example provided in left-right symmetric model

Abstract

It is known that a keV scale sterile neutrino is a good warm dark matter candidate. We study how this possibility could be realized in the context of gauge extensions of the standard model. The na\"ive expectation leads to large thermal overproduction of sterile neutrinos in this setup. However, we find that it is possible to use out-of-equilibrium decay of the other right-handed neutrinos of the model to dilute the present density of the keV sterile neutrinos and achieve the observed dark matter density. We present the universal requirements that should be satisfied by the gauge extensions of the standard model, containing right-handed neutrinos, to be viable models of warm dark matter, and provide a simple example in the context of the left-right symmetric model.