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

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.

Proceedings for the "17th International Conference on Topics in Astroparticle and Underground Physics" (TAUP 2021). Based on Phys.Rev.Lett. 124 (2020) 8, 081802, and Phys.Rev.Lett. 127 (2021) 4, 041101