Scaling in the neutrino mass matrix, μ–τ symmetry and the see-saw mechanism

摘要

The scaling hypothesis postulates proportionality of two columns of the Majorana neutrino mass matrix in the flavor basis. This ansatz was shown to lead to an inverted hierarchy and Ue3 = 0. We discuss theoretical and phenomenological properties of this hypothesis. We show that (i) the neutrino mass matrix with scaling follows as a consequence of a generalized μ–τ symmetry imposed on the type-I see-saw model; (ii) there exists a unique texture for the Dirac mass matrix mD which leads to scaling for arbitrary Majorana matrix MR in the context of the type-I see-saw mechanism; (iii) unlike in the μ–τ symmetric case, a simple model with two right-handed neutrinos and scaling can lead to successful leptogenesis both with and without the inclusion of flavor effects.