Realistic sterile neutrino dark matter with keV mass does not contradict cosmological bounds

TL;DR

This paper demonstrates that keV-mass sterile neutrinos produced resonantly can serve as viable dark matter candidates without conflicting with cosmological constraints, challenging previous assumptions about their exclusion.

Contribution

It shows that resonantly produced sterile neutrinos with masses as low as 2 keV are compatible with cosmological data, expanding the viable parameter space for dark matter models.

Findings

Sterile neutrinos with ≥2 keV can account for all dark matter.

Resonant production models align with neutrino oscillation and baryogenesis data.

Cosmological signatures resemble mixed Cold plus Warm Dark Matter models.

Abstract

Previous fits of sterile neutrino dark matter models to cosmological data assumed a peculiar production mechanism, which is not representative of the best-motivated particle physics models given current data on neutrino oscillations. These analyses ruled out sterile neutrino masses smaller than 8-10 keV. Here we focus on sterile neutrinos produced resonantly. We show that their cosmological signature can be approximated by that of mixed Cold plus Warm Dark Matter (CWDM). We use recent results on LambdaCWDM models to show that for each mass greater than or equal to 2 keV, there exists at least one model of sterile neutrino accounting for the totality of dark matter, and consistent with Lyman-alpha and other cosmological data. Resonant production occurs in the framework of the nuMSM (the extension of the Standard Model with three right-handed neutrinos). The models we checked to be allowed correspond to parameter values consistent with neutrino oscillation data, baryogenesis and all other dark matter bounds.