Lepton Number-Driven Sterile Neutrino Production in the Early Universe

TL;DR

This paper investigates how lepton number influences sterile neutrino production in the early universe, revealing resonance effects that shape the resulting dark matter energy spectra.

Contribution

It introduces a detailed quantum kinetic approach to model lepton number-driven sterile neutrino production, highlighting resonance phenomena and spectral features.

Findings

Resonances occur with significant lepton asymmetry, enhancing sterile neutrino production.

Relic sterile neutrino spectra are sharply peaked in energy due to resonance evolution.

Quantum kinetic treatment provides insights beyond the quantum Zeno approximation.

Abstract

We examine medium-enhanced, neutrino scattering-induced decoherent production of dark matter candidate sterile neutrinos in the early universe. In cases with a significant net lepton number we find two resonances, where the effective in-medium mixing angles are large. We calculate the lepton number depletion-driven evolution of these resonances. We describe the dependence of this evolution on lepton numbers, sterile neutrino rest mass, and the active-sterile vacuum mixing angle. We find that this resonance evolution can result in relic sterile neutrino energy spectra with a generic form which is sharply peaked in energy. We compare our complete quantum kinetic equation treatment with the widely-used quantum Zeno ansatz.