Neutrino decay into fermionic quasiparticles in leptogenesis

TL;DR

This paper calculates the decay rate of the lightest heavy Majorana neutrino in a thermal environment, revealing significant deviations from traditional methods due to altered leptonic dispersion relations, impacting leptogenesis models.

Contribution

It introduces a novel finite temperature calculation of neutrino decay rates using cutting rules and effective Green's functions, highlighting the importance of dispersion relations.

Findings

Decay rate differs by over an order of magnitude from traditional estimates.

Thermal effects significantly modify leptonic dispersion relations.

Results impact the understanding of neutrino decay in the early universe.

Abstract

We calculate the decay rate of the lightest heavy Majorana neutrino in a thermal bath using finite temperature cutting rules and effective Green's functions according to the hard thermal loop resummation technique. Compared to the usual approach where thermal masses are inserted into the kinematics of final states, we find that deviations arise through two different leptonic dispersion relations. The decay rate differs from the usual approach by more than one order of magnitude in the temperature range which is interesting for the weak washout regime. This work summarizes the results of Ref. [1], to which we refer the interested reader.