Neutrino masses from U(1) symmetries and the Super-Kamiokande data

Motivated by the Super-Kamiokande data, we revisit models with U(1) symmetr ies and discuss the origin of neutrino masses and mixings in such theories. We show that, in models with just three light neutrinos and a hierarchy of neutrino masses, large (2-3) mixing fixes the lepton doublet U(1) charges and is thus related to the structure of the charged lepton mass matrix. We discuss the fermion mass structure that follows from the abelian family sym metry with an extended gauge group. Requiring that the quark and lepton mas ses be ordered by the family symmetry, we identify the most promising schem e. This requires large, but not necessarily maximal, mixing in the mu tau s ector and gives e mu mixing in the range that is required for the small ang le solution of the solar neutrino deficit. (C) 1999 Elsevier Science B.V. A ll rights reserved.