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

TL;DR

This paper explores the scaling hypothesis in the neutrino mass matrix, linking it to mu-tau symmetry and the see-saw mechanism, and demonstrates its implications for neutrino hierarchy, leptogenesis, and model textures.

Contribution

It shows that the scaling hypothesis arises from a generalized mu-tau symmetry in the type-I see-saw model and identifies a unique Dirac mass matrix texture compatible with this scaling.

Findings

Scaling leads to inverted hierarchy and zero U_{e3}.

Scaling results from a generalized mu-tau symmetry in the see-saw model.

A simple two right-handed neutrino model with scaling can successfully produce leptogenesis.

Abstract

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 U_{e3} = 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 mu-tau symmetry imposed on the type-I see-saw model; (ii) there exists a unique texture for the Dirac mass matrix m_D which leads to scaling for arbitrary Majorana 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-handed neutrinos and scaling can lead to successful leptogenesis both with and without the inclusion of flavor effects.