Tri-resonant leptogenesis in a seesaw extension of the Standard Model

• Published in: The journal of high energy physics 2022-11, Vol.2022 (11), p.65-38, Article 65
• Main Authors: Candia da Silva, P., Karamitros, D., McKelvey, T., Pilaftsis, A.
• Format: Article
• Language: English
• Subjects: Asymmetry; Baryo-and Leptogenesis; Classical and Quantum Gravitation; Degrees of freedom; Early Universe Particle Physics; Elementary Particles; Evolution; Flavor (particle physics); High energy physics; Leptons; Mathematical models; Neutrino Mixing; Neutrinos; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Regular Article - Theoretical Physics; Relativistic effects; Relativity Theory; Sterile or Heavy Neutrinos; String Theory; Temperature dependence
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP11(2022)065

A bstract We study a class of leptogenesis models where the light neutrinos acquire their observed small masses by a symmetry-motivated construction. This class of models may naturally include three nearly degenerate heavy Majorana neutrinos that can strongly mix with one another and have mass differences comparable to their decay widths. We find that such a tri-resonant heavy neutrino system can lead to leptonic CP asymmetries which are further enhanced than those obtained in the usual bi-resonant approximation. Moreover, we solve the Boltzmann equations by paying special attention to the temperature dependence of the relativistic degrees of freedom of the plasma. The latter results in significant corrections to the evolution equations for the heavy neutrinos and the lepton asymmetry that have been previously ignored in the literature. We show the importance of these corrections to accurately describe the dynamical evolution of the baryon-to-photon ratio η B for heavy neutrino masses at and below 100 GeV, and demonstrate that successful leptogenesis at lower masses can be significantly affected by the variation of the relativistic degrees of freedom. The parameter space for the leptogenesis model is discussed, and it could be probed in future experimental facilities searching for charged lepton flavour violation and heavy neutrinos in future Z -boson factories.