The origin of the light neutrino masses, and the baryon asymmetry of the Universe remain some of the major questions of particle physics. Both of these problems can be solved if we extend the standard model by two right-handed neutrinos. The light neutrino masses can be generated through the type-I seesaw mechanism, and the baryon asymmetry of the Universe through leptogenesis.
In particular, we will consider two realizations of the leptogenesis mechanism: leptogenesis through neutrino oscillations, which is the dominant mechanism for heavy neutrinos with masses below the electroweak scale and resonant leptogenesis, which assumes heavy neutrinos with masses above the electroweak scale. We will discuss the similarities and differences between them and demonstrate how the smooth transition between these regimes makes leptogenesis possible for heavy neutrinos with masses from 100 MeV up to masses where flavoured leptogenesis takes over.
