# GeV-scale hot sterile neutrino oscillations: a derivation of evolution equations

## TL;DR

This paper derives evolution equations for GeV-scale sterile neutrinos and active lepton densities, incorporating detailed scattering processes and helicity effects, to better understand leptogenesis at high temperatures.

## Contribution

It provides a systematic derivation of non-equilibrium evolution equations including helicity and scattering effects for sterile neutrinos at GeV scale.

## Key findings

- Derived equations governing sterile neutrino and lepton densities.
- Accounted for LPM resummation and all relevant scatterings.
- Analyzed the decoupling of sphaleron processes.

## Abstract

Starting from operator equations of motion and making arguments based on a separation of time scales, a set of equations is derived which govern the non-equilibrium time evolution of a GeV-scale sterile neutrino density matrix and active lepton number densities at temperatures T > 130 GeV. The density matrix possesses generation and helicity indices; we demonstrate how helicity permits for a classification of various sources for leptogenesis. The coefficients parametrizing the equations are determined to leading order in Standard Model couplings, accounting for the LPM resummation of 1+n <-> 2+n scatterings and for all 2 <-> 2 scatterings. The regime in which sphaleron processes gradually decouple so that baryon plus lepton number becomes a separate non-equilibrium variable is also considered.

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Source: https://tomesphere.com/paper/1703.06087