GeV-scale hot sterile neutrino oscillations: a numerical solution

TL;DR

This paper provides a comprehensive numerical solution to the complex equations governing baryogenesis via GeV-scale sterile neutrino oscillations, highlighting the importance of full momentum and helicity dependence.

Contribution

It introduces a detailed numerical approach incorporating full momentum and helicity dependence, improving accuracy over previous simplified models.

Findings

Density matrix deviates from kinetic equilibrium

IR modes equilibrate faster than UV modes

Final results differ by ~50% from recent benchmarks

Abstract

The scenario of baryogenesis through GeV-scale sterile neutrino oscillations is governed by non-linear differential equations for the time evolution of a sterile neutrino density matrix and Standard Model lepton and baryon asymmetries. By employing up-to-date rate coefficients and a non-perturbatively estimated Chern-Simons diffusion rate, we present a numerical solution of this system, incorporating the full momentum and helicity dependences of the density matrix. The density matrix deviates significantly from kinetic equilibrium, with the IR modes equilibrating much faster than the UV modes. For equivalent input parameters, our final results differ moderately (~50%) from recent benchmarks in the literature. The possibility of producing an observable baryon asymmetry is nevertheless confirmed. We illustrate the dependence of the baryon asymmetry on the sterile neutrino mass splitting and on the CP-violating phase measurable in active neutrino oscillation experiments.