Flavour-Covariant Rate Equations for Resonant Leptogenesis

Scenarios of leptogenesis provide a mechanism for generating the observed baryon asymmetry of the Universe, while also explaining the light neutrino masses. The former is generated by decays of heavy right-handed Majorana neutrinos in the early Universe and the latter, by means of the see-saw mechanism. Moreover, in scenarios of Resonant Leptogenesis (RL), the masses of the Majorana neutrinos can be at the electroweak scale, whilst maintaining sizable couplings to standard model fermions. Thus, such models may be testable at current and future experiments, including the LHC.

The final lepton asymmetry is obtained by solving systems of transport equations, describing the evolution of particle number densities. We present a fully flavour-covariant formulation of transport phenomena and illustrate that the final asymmetry in RL depends upon three distinct flavour effects: (i) oscillations and (ii) resonant mixing between heavy-neutrino flavours as well as (iii) (de)coherence in the charged-lepton sector. By accounting consistently for these effects, we show that the final asymmetry may be enhanced by as much as an order of magnitude, compared to partially flavoured treatments.