Sterile neutrino dark matter, neutrino secret self-interactions, and extra radiation

TL;DR

This paper proposes that secret self-interactions among active neutrinos can produce keV-scale sterile neutrino dark matter efficiently, avoiding X-ray constraints and offering testable signatures in experiments and cosmology.

Contribution

It introduces a novel mechanism involving neutrino self-interactions mediated by a scalar to generate sterile neutrino dark matter.

Findings

Self-interactions enable sterile neutrino production without X-ray constraints.

Testable signatures in laboratory experiments for mediators > a few MeV.

Observable cosmological effects for lighter mediators.

Abstract

keV scale sterile neutrinos are excellent warm dark matter candidates. In the early Universe, these can be produced from oscillations and scatterings of active neutrinos. However, in the absence of any new physics, this mechanism is in severe tension with observations from X-ray searches. In this work, we show that secret self-interactions of active neutrinos, mediated by a scalar, can efficiently produce these sterile neutrinos without being ruled out by X-ray observations. These neutrino self-interactions are also testable: for a mediator mass greater than a few MeV, these self-interactions can give signatures in laboratory based experiments, while for lighter mediators, there will be observable consequences for upcoming cosmology probes.