Neutrino physics from a U(2) flavor symmetry

We consider the neutrino physics of models with a sequentially broken U(2) flavor symmetry. Such theories yield the observed pattern of quark and lepton masses, while maintaining sufficient degeneracies between superparticles of the first two generations to solve the supersymmetric flavor problem. Neutrino mass ratios and mixing angles in these models may differ significantly from those of the charged leptons, even though the neutrinos and charged leptons transform identically under the flavor group. A wide class of well-motivated U(2) theories yield order one ν_μ-ν_τ mixing, without a fine-tuning of parameters. These models provide a natural solution to the atmospheric neutrino deficit, and also have distinctive signatures at long-baseline neutrino oscillation experiments.