Axion-Sterile-Neutrino Dark Matter

TL;DR

This paper explores a comprehensive model extending the Standard Model with axions and sterile neutrinos, addressing multiple fundamental issues like dark matter, neutrino oscillations, and the strong CP problem, while analyzing various dark matter production mechanisms.

Contribution

It provides a general analysis of dark matter in the $a u$MSM, connecting axion and neutrino parameters, and rules out primordial black holes as a dark matter source within this model.

Findings

Dark matter cannot originate from primordial black holes in this model.

The model predicts a multicomponent dark matter consisting of axions and sterile neutrinos.

It links axion decay constants to neutrino parameters.

Abstract

Extending the Standard Model with three right-handed neutrinos and a simple QCD axion sector can account for neutrino oscillations, dark matter and baryon asymmetry; at the same time, it solves the strong CP problem, stabilizes the electroweak vacuum and can implement critical Higgs inflation (satisfying all current observational bounds). We perform here a general analysis of dark matter (DM) in such a model, which we call the $a\nu$MSM. Although critical Higgs inflation features a (quasi) inflection point of the inflaton potential we show that DM cannot receive a contribution from primordial black holes in the $a\nu$MSM. This leads to a multicomponent axion-sterile-neutrino DM and allows us to relate the axion parameters, such as the axion decay constant, to the neutrino parameters. We include several DM production mechanisms: the axion production via misalignment and decay of topological defects as well as the sterile-neutrino production through the resonant and non-resonant mechanisms and in the recently proposed CPT-symmetric universe.