U(2)and maximal mixing ofνμ

A $U\left(2\right)\mathrm{}$ flavor symmetry can successfully describe charged fermion masses and mixings, and suppress SUSY FCNC processes, making it a viable candidate for a theory of flavor. We show that a direct application of this $U\left(2\right)\mathrm{}$ flavor symmetry automatically predicts a mixing of 45° for ${\nu }_{\mu }\Rightarrow {\nu }_s,$ where ${\nu }_s$ is a light, right-handed state. The introduction of an additional flavor symmetry acting on the right-handed neutrinos makes the model phenomenologically viable, explaining the solar neutrino deficit as well as the atmospheric neutrino anomaly, while giving a potential hot dark matter candidate and retaining the theory’s predictivity in the quark sector.