Cosmological Dependence of Sterile Neutrino Dark Matter With Self-Interacting Neutrinos

TL;DR

This paper investigates how uncertainties in early Universe cosmology and neutrino self-interactions influence the parameter space for sterile neutrino dark matter, revealing a significantly expanded viable range for their role as dark matter.

Contribution

It introduces an analysis of the impact of pre-BBN cosmological uncertainties on sterile neutrino dark matter production via active neutrino self-interactions.

Findings

Uncertainties in early Universe cosmology expand sterile neutrino parameter space.

Self-interacting neutrinos can produce keV-mass sterile neutrinos before BBN.

The viable parameter space for sterile neutrino dark matter is significantly larger than previously thought.

Abstract

Unexplored interactions of neutrinos could be the key to understanding the nature of the dark matter (DM). In particular, active neutrinos with new self-interactions can produce keV-mass sterile neutrinos that account for the whole of the DM through the Dodelson-Widrow mechanism for a large range of active-sterile mixing values. This production typically occurs before Big-Bang Nucleosynthesis (BBN) in a yet uncharted era of the Universe. We assess how the mixing range for keV-mass sterile neutrino DM is affected by the uncertainty in the early Universe pre-BBN cosmology. This is particularly relevant for identifying the viable parameter space of sterile neutrino searches allowed by all astrophysical limits, as well as for cosmology, since the detection of a sterile neutrino could constitute the first observation of a particle providing information about the pre-BBN epoch. We find that the combined uncertainties in the early Universe cosmology and neutrino interactions significantly expand the allowed parameter space for sterile neutrinos that can constitute the whole of the DM.