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

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 ?-? interchange symmetry, enforcing—at tree level—maximal atmospheric neutrino mixing and a vanishing mixing angle ?13. The small ratio m?/m? (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.