Sterile neutrino dark matter as a consequence of nuMSM-induced lepton asymmetry

TL;DR

This paper investigates sterile neutrino dark matter production in the nuMSM framework, using quantum field theory to refine relic density calculations and confronts these with astrophysical data to set bounds on neutrino properties.

Contribution

It provides a quantum field theoretic re-computation of sterile neutrino relic density and momentum distribution in the nuMSM, improving constraints on dark matter candidates.

Findings

Refined relic density calculations for sterile neutrinos.

Derived astrophysical bounds on sterile neutrino properties.

Spectra useful for structure formation and small-scale structure analysis.

Abstract

It has been pointed out in ref.[1] that in the nuMSM (Standard Model extended by three right-handed neutrinos with masses smaller than the electroweak scale), there is a corner in the parameter space where CP-violating resonant oscillations among the two heaviest right-handed neutrinos continue to operate below the freeze-out temperature of sphaleron transitions, leading to a lepton asymmetry which is considerably larger than the baryon asymmetry. Consequently, the lightest right-handed (``sterile'') neutrinos, which may serve as dark matter, are generated through an efficient resonant mechanism proposed by Shi and Fuller [2]. We re-compute the dark matter relic density and non-equilibrium momentum distribution function in this situation with quantum field theoretic methods and, confronting the results with existing astrophysical data, derive bounds on the properties of the lightest right-handed neutrinos. Our spectra can be used as an input for structure formation simulations in warm dark matter cosmologies, for a Lyman-alpha analysis of the dark matter distribution on small scales, and for studying the properties of haloes of dwarf spheroidal galaxies.