Flavour effects on leptogenesis predictions

Abstract

We show that flavour effects in leptogenesis reduce the region of the seesaw parameterspace where the final predictions do not depend on the initial conditions, the strongwash-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 getrelaxed compared to the usual ones in the one-flavour approximation, GeV. Flavour effects can however relax down to these minimal valuesthe lower bounds holding for fixed large values of the decay parameterK1. We discuss a relevant definite example showing that, when the known information on theneutrino mixing matrix is employed, the lower bounds for are relaxed by a factor 2–3 for fully hierarchical light neutrinos, without any dependence onθ13 and on possible phases. On the other hand, going beyond the limit of hierarchical lightneutrinos and taking into account Majorana phases, the lower bounds can be relaxed byone order of magnitude. Therefore, Majorana phases can play an important role inleptogenesis when flavour effects are included.