A light pseudoscalar in a model with lepton family symmetry O(2)

TL;DR

This paper explores a model with O(2) lepton family symmetry that naturally explains maximal atmospheric neutrino mixing and predicts a light pseudoscalar particle consistent with experimental constraints.

Contribution

It introduces a novel realization of O(2) symmetry in the lepton sector, linking mu-tau symmetry to a light pseudoscalar without conflicting with experiments.

Findings

Maximal atmospheric neutrino mixing is achieved at tree level.

A light pseudoscalar arises naturally due to muon-tau mass ratio.

The model remains consistent with current experimental bounds.

Abstract

We discuss a realization of the non-abelian group O(2) as a family symmetry for the lepton sector. The reflection contained in O(2) acts as a mu-tau interchange symmetry, enforcing--at tree level--maximal atmospheric neutrino mixing and a vanishing mixing angle theta_13. The small ratio m_mu/m_tau (muon over tau mass) gives rise to a suppression factor in the mass of one of the pseudoscalars of the model. We argue that such a light pseudoscalar does not violate any experimental constraint.