Towards leptogenesis at NLO: the right-handed neutrino interaction rate

TL;DR

This paper calculates next-to-leading order quantum and thermal corrections to the right-handed neutrino interaction rate in the early universe, resolving previous infra-red divergence issues and providing a more accurate basis for leptogenesis models.

Contribution

It provides the first comprehensive NLO computation of the neutrino interaction rate including all relevant SM couplings, ensuring infra-red divergences cancel as required by the KLN theorem.

Findings

Infra-red divergences cancel when including 1->3 and virtual corrections.

The corrected interaction rate is more precise for leptogenesis models.

The work sets a new standard for NLO calculations in early universe neutrino interactions.

Abstract

We compute quantum and thermal corrections to the right-handed neutrino interaction rate in the early universe at next-to-leading order in all the relevant SM couplings (gauge, top Yukawa and higgs couplings). Previous computations considered 2 -> 2 scatterings, finding infra-red divergences. The KLN theorem demands that infra-red divergences cancel in the full result: after adding 1 -> 3 and one-loop virtual corrections that enter at the same order we find a simple result.