Axion-assisted Resonance Oscillation Rescues the Dodelson-Widrow Mechanism

TL;DR

This paper proposes an axion-assisted mechanism that enhances sterile neutrino production, resolving conflicts in the Dodelson-Widrow model by introducing effective interactions that increase conversion probability with smaller mixing angles.

Contribution

It introduces a novel axion-assisted interaction that boosts sterile neutrino production, alleviating astrophysical constraints on the Dodelson-Widrow mechanism.

Findings

Enhanced sterile neutrino production rate.

Reduced mixing angle needed for dark matter abundance.

Potential resolution of astrophysical constraints.

Abstract

The $\rm{keV}$ scale sterile neutrino was a qualified candidate for dark matter particles in the Dodelson-Widrow mechanism. But the mixing angle, needed to provide enough amount of dark matter, is in contradiction with the astrophysical observations. To alleviate such tension, we introduce an effective interaction, i.e. $g_a (\phi/\Lambda)\partial_{\mu}a \overline{\nu_\alpha}\gamma^{\mu} \gamma_5 \nu_\alpha$, among Standard Model neutrino $\nu_\alpha$, axion $a$, and singlet $\phi$. The axial-vector interaction form is determined by the axion shift symmetry, and the singlet $\phi$ with dynamically varied vacuum expectation value is introduced to reinforce the axial-vector coupling strength and evade the stringent neutrino oscillation constraints. The effective potential generated by the new interaction {could cancel} the SM counterpart, resulting in an {enhanced converting} probability between SM neutrino and sterile neutrino. Hence, the production rate of sterile neutrinos can be substantially enlarged with smaller mixing compared to the DW mechanism.