This thesis considers the role of singlet neutrinos in the generation of an appreciable baryon asymmetry in the early Universe. We complete an in-depth analysis of different physical phenomena that contribute to the CP asymmetry and the inclusion of out-of-equilibrium effects. In the case of the former, we critically consider the dynamics of unstable two-level systems and identify physically distinct regions of the parameter space through a geometric decomposition of the effective Hamiltonian. In the case that the so-called decay, Î, and energy, E, vectors are orthogonal to each other and the dimensionless parameter r = |Î|/(2|E|) is below unity, we observe non-trivial phenomena, such as coherence-decoherence oscillations, and the inhomogeneous rotation of the Bloch vector, which sweeps out unequal areas in equal times. In the study of an appreciable baryon asymmetry, we consider a symmetry-motivated Yukawa structure, which offers naturally light neutrino masses as well as large CP phases. We consider a set of transport equations and, crucially, preserve the temperature dependence of the relativistic degrees of freedom. We then analyse their impact on the generated baryon asymmetry, with large deviations found in models with heavy neutrinos below the electroweak scale. Finally, we make pertinent comparisons with current and future experiments, with a focus on cLFV processes.
- Heavy Neutrinos
- Critical Qubits
- Degrees of Freedom
- Baryon Asymmetry
- Leptogenesis
Novel Resonant Mechanisms for Generating Matter-Antimatter Asymmetry in Minimal Extensions of the Standard Model
Mckelvey, T. (Author). 1 Aug 2024
Student thesis: Phd