Leptogenesis within a generalized quark-lepton symmetry
Abstract
Quark-lepton symmetry has been shown to be inconsistent with baryogenesis via leptogenesis in natural schemes of the see-saw mechanism. Within the phenomenological approach of textures, we relax this strict symmetry and propose weaker conditions, namely models of the neutrino Dirac mass matrix MD which have the same hierarchy as the matrix elements of Mu. We call this guide-line generalized hierarchical quark-lepton symmetry. We consider in detail particular cases in which the moduli of the matrix elements of MD are equal to those of Mu. Within the phenomenological approach of textures, we try for the heavy Majorana mass matrix diagonal and off-diagonal forms. We find that an ansatz for MD preserving the hierarchy, together with an off-diagonal model for the heavy Majorana neutrino mass, is consistent with neutrino masses, neutrino mixing and baryogenesis via leptogenesis for an intermediate mass scale mR 1012 GeV. The preservation of the hierarchical structure could come from a possible symmetry scheme.