Maximal atmospheric neutrino mixing and the small ratio of muon to tau mass

Abstract

We discuss the problem of the small ratio of muon mass to tau mass in a class of seesaw models where maximal atmospheric neutrino mixing is enforced through a $\mu$--$\tau$ interchange symmetry. We introduce into those models an additional symmetry $T$ such that $m_{\mu }=0$ in the case of exact $T$ invariance. The symmetry $T$ may be softly broken in the Higgs potential, and one thus achieves $m_{\mu }\ll m_{\tau }$ in a technically natural way. We speculate on a wider applicability of this mechanism.

Comments: 10 pages, plain LaTeX, no figures, minor changes, final version for J. Phys. G