Flavour effects on leptogenesis predictions

Abstract

We show that flavour effects in leptogenesis reduce the region of the seesaw parameter space where the final predictions do not depend on the initial conditions, the strong wash-out regime. In this case the lowest bounds holding on the lightest right-handed (RH) neutrino mass and on the reheating temperature for hierarchical heavy neutrinos do not get relaxed compared to the usual ones in the one-flavour approximation, GeV. Flavour effects can however relax down to these minimal values the lower bounds holding for fixed large values of the decay parameter K 1 . We discuss a relevant definite example showing that, when the known information on the neutrino mixing matrix is employed, the lower bounds for are relaxed by a factor 2–3 for fully hierarchical light neutrinos, without any dependence on θ 13 and on possible phases. On the other hand, going beyond the limit of hierarchical light neutrinos and taking into account Majorana phases, the lower bounds can be relaxed by one order of magnitude. Therefore, Majorana phases can play an important role in leptogenesis when flavour effects are included.