Sterile neutrino dark matter catalyzed by a very light dark photon

TL;DR

This paper proposes a new mechanism where a very light dark photon induces resonant oscillations between active and sterile neutrinos, enabling sterile neutrinos to be viable dark matter candidates without conflicting with existing constraints.

Contribution

It introduces a novel resonant production mechanism for sterile neutrino dark matter via coupling to a light dark photon condensate, expanding the parameter space.

Findings

Resonant oscillations allow sterile neutrinos to be dark matter.

The mechanism is consistent with X-ray constraints.

Potential deviations in solar and atmospheric neutrino oscillations.

Abstract

Sterile neutrinos ($\nu_s$) that mix with active neutrinos ($\nu_a$) are interesting dark matter candidates with a rich cosmological and astrophysical phenomenology. In their simplest incarnation, their production is severely constrained by a combination of structure formation observations and X-ray searches. We show that if active neutrinos couple to an oscillating condensate of a very light $L_{\mu}-L_{\tau}$ gauge field, resonant $\nu_a$-$\nu_s$ oscillations can occur in the early universe, consistent with $\nu_s$ constituting all of the dark matter, while respecting X-ray constraints on $\nu_s\to\nu_a\gamma$ decays. Interesting deviations from standard solar and atmospheric neutrino oscillations can persist to the present.