CP asymmetry factor in decays at finite temperature

Key Points

Leptogenesis predicts changes in CP asymmetry factors at high temperatures, which can impact matter-antimatter asymmetry.
Mass generation parameters significantly influence the finite-temperature decay behavior of Majorana neutrinos.
Observational evaluation applies one-loop calculations to assess thermal CP asymmetry across various processes in particle physics.
Findings highlight the necessity for accurate thermal modeling in understanding CP violation and its implications for the universe's matter content.

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 Nᵢ ϕ+ L and ϕ Nᵢ+L at temperatures where they are kinematically allowed. We present a numerical comparison with previous formulae given in the literature.

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