Scaling in the Neutrino Mass Matrix, mu-tau Symmetry and the See-Saw Mechanism

摘要

The scaling hypothesis postulates proportionality of two columns of theMajorana neutrino mass matrix in the flavor basis. This Ansatz was shown tolead to an inverted hierarchy and U_{e3} = 0. We discuss theoretical andphenomenological properties of this hypothesis. We show that (i) the neutrinomass matrix with scaling follows as a consequence of a generalized mu-tausymmetry imposed on the type-I see-saw model; (ii) there exists a uniquetexture for the Dirac mass matrix m_D which leads to scaling for arbitraryMajorana matrix M_R in the context of the type-I see-saw mechanism; (iii)unlike in the mu-tau symmetric case, a simple model with two right-handedneutrinos and scaling can lead to successful leptogenesis both with and withoutthe inclusion of flavor effects.