https://doi.org/10.1140/epjc/s10052-025-15015-x
Letter
CP asymmetry factor in decays at finite temperature
1
Department of Theoretical Physics, ELTE Eötvös Loránd University, Pázmány Péter sétány 1/A, 1117, Budapest, Hungary
2
II. Institut für Theoretische Physik, Universität Hamburg, Luruper Chaussee 149, 22761, Hamburg, Germany
3
HUN-REN ELTE Theoretical Physics Research Group, Pázmány Péter sétány 1/A, 1117, Budapest, Hungary
a
karoly.seller@uni-hamburg.de
Received:
21
March
2025
Accepted:
1
November
2025
Published online:
13
November
2025
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 
and 
at temperatures where they are kinematically allowed. We present a numerical comparison with previous formulae given in the literature.
© The Author(s) 2025
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Funded by SCOAP3.
