CP asymmetry factor in decays at finite temperature

TL;DR

This paper provides a comprehensive leading-order calculation of the CP asymmetry factor in finite-temperature decays involving Majorana neutrinos, crucial for understanding matter-antimatter asymmetry in leptogenesis.

Contribution

It offers the complete one-loop evaluation of thermal CP asymmetry factors at finite temperature, including all necessary details for accurate predictions.

Findings

Numerical comparison with previous formulas shows improved accuracy.

Thermal effects significantly influence CP asymmetry predictions.

Provides a framework for reliable matter-antimatter asymmetry estimates.

Abstract

We present in the conventional equilibrium approach to leptogenesis the complete leading order prediction for the CP asymmetry factor in finite-temperature decays involving Majorana neutrinos. As thermal effects are generally not negligible, the knowledge of the high temperature behavior of the underlying particle physics model, in particular that of mass generation, is required for reliable estimates of matter-antimatter asymmetry through the mechanism of leptogenesis. We present all necessary information needed to obtain the full one-loop evaluation for the thermal CP asymmetry factors for the processes $N_i\to \phi + L$ and $\phi \to N_i+L$ at temperatures where they are kinematically allowed. We present a numerical comparison with previous formulae given in the literature.