Sterile neutrino dark matter via coinciding resonances

Abstract

It has been proposed that two resonances could coincide in the early universe at temperatures $T\sim \mathrm{0.2...0.5}$ GeV: one between two nearly degenerate GeV-scale sterile neutrinos, producing a large lepton asymmetry through freeze-out and decays; another between medium-modified active neutrinos and keV-scale sterile neutrinos, converting the lepton asymmetry into dark matter. Making use of a framework which tracks three sterile neutrinos of both helicities as well as three separate lepton asymmetries, and scanning the parameter space of the GeV-scale species, we establish the degree of fine-tuning that is needed for realizing this scenario.

Comments: 14 pages. v2: clarification added