Flavoured CP-asymmetry at the effective neutrino mass floor

Abstract

Both neutrinoless double beta decay and leptogenesis require neutrinos to be Majorana fermions. A relation between these two phenomena can be derived once the mechanism of neutrino mass generation is specified. Using the current data from the neutrino oscillations, we constrain the Majorana phases of the neutrino mixing matrix by minimising the effective neutrino mass in neutrinoless double beta decay. Given these Majorana phases at the effective neutrino mass floor, we show that it is possible to obtain a large enough CP asymmetry (≥10−8) required for adequate leptogenesis, without additional phases at high scale. Such scenario pushes the lower bound on M1 (the mass of the lightest of the heavy neutrinos in the Type-I see-saw mechanism) to a higher value compared to the usual Davidson-Ibarra bound. In particular, we find that M1≥1010(109) GeV for the case of Normal (Inverted) hierarchy. We extend our analysis to the case when one of the heavy neutrinos decouples (two right handed neutrino models). In this case we find M1≥1010(1011) GeV for the case of Normal (Inverted) hierarchy.