On different approaches to freeze-in and freeze-out leptogenesis with quasi-degenerate neutrinos

J. Racker

doi:10.1140/epjc/s10052-023-11321-4

2022 Impact factor 4.4

Particles and Fields

Open Access

Eur. Phys. J. C (2023) 83: 170
https://doi.org/10.1140/epjc/s10052-023-11321-4

Regular Article - Theoretical Physics

On different approaches to freeze-in and freeze-out leptogenesis with quasi-degenerate neutrinos

J. Racker¹^,2^a

¹ Instituto de Astronomía Teórica y Experimental (IATE), Universidad Nacional de Córdoba (UNC)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Laprida 854, X5000BGR, Córdoba, Córdoba, Argentina
² Observatorio Astronómico de Córdoba (OAC), Universidad Nacional de Córdoba (UNC), Laprida 854, X5000BGR, Córdoba, Córdoba, Argentina

^a jracker@unc.edu.ar

Received: 19 December 2022
Accepted: 12 February 2023
Published online: 22 February 2023

Abstract

We compare two approaches for determining the generation of lepton asymmetry during production and decay of quasi-degenerate neutrinos, namely the density matrix formalism and a recent proposal which does not involve any counting of neutrino number densities and is based on plugging the resummed propagator in a quantum field theory model for neutrino oscillations. We show numerically and analytically that they are almost equivalent for small mass splittings and also discuss the hierarchical limit. The comparison, performed in a simple scalar toy model, helps to understand several issues that have been discussed in the literature.

© The Author(s) 2023

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/.