Neutrino collective effects and sterile neutrino production in the early universe

TL;DR

This paper investigates how neutrino-neutrino interactions in the early universe can significantly boost sterile neutrino production via the Dodelson-Widrow mechanism, potentially explaining dark matter even with weak active-sterile couplings.

Contribution

It demonstrates that standard model neutrino interactions can enhance sterile neutrino production, expanding the viable parameter space for sterile neutrino dark matter.

Findings

Neutrino self-interactions can increase sterile neutrino production in the early universe.

Enhanced production occurs in the temperature range 5-15 MeV.

Sterile neutrinos can account for dark matter with small active-sterile couplings.

Abstract

Neutrino-neutrino interactions, as mediated by standard model Z exchange, can drastically enhance the Dodelson-Widrow mechanism for the production of sterile neutrinos in the region of temperature $5-15$MeV. For a sterile mass in the KeV region with the usual type of active-sterile neutrino coupling, the production can be copious enough to provide ample dark matter, even when the active-sterile coupling is small enough to avoid the bounds set by laboratory results.