Resonant enhancement in leptogenesis

Understand

Vanilla leptogenesis within the type I seesaw framework requires the mass scale of the right-handed neutrinos to be above 10^9 GeV.

• This lower bound can be avoided if at least two of the sterile states are almost mass degenerate, which leads to an enhancement of the decay asymmetry.
• Leptogenesis models that can be tested in current and upcoming experiments often rely on this resonant enhancement, and a systematic and consistent description is therefore necessary for phenomenological applications.
• In this review article, we give an overview of different methods that have been used to study the saturation of the resonant enhancement when the mass difference becomes comparable to the characteristic width of the Majorana neutrinos.