mu-tau Interchange symmetry and lepton mixing

TL;DR

This paper explores mu-tau interchange symmetry as a means to explain lepton mixing features, reviewing models based on the seesaw mechanism and soft symmetry breaking, and discusses naturalness arguments for mass ratios.

Contribution

It introduces models utilizing mu-tau symmetry and generalized CP symmetry to explain lepton mixing and mass ratios, expanding theoretical understanding.

Findings

Models achieve maximal atmospheric neutrino mixing

Symmetry can be embedded in generalized CP symmetry

Naturalness arguments explain small mass ratios

Abstract

We focus on the use of a mu-tau interchange symmetry to explain features of lepton mixing, especially maximal atmospheric neutrino mixing. We review two models which achieve this goal and are based on the seesaw mechanism and on the soft breaking of the family-lepton-number symmetries. We also note that that symmetry may be embedded in a generalized CP symmetry. We show that, in the context of some of our models, arguments of naturalness may be used for explaining the smallness of the mass ratio m_mu / m_tau.