Pseudo-Dirac Solar Neutrinos

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Three of the viable solutions of the solar neutrino problem are consistent with close to maximal leptonic mixing: ²θ₁₂=12(1-ε₁₂) with |ε₁₂|≪1. Flavor models can naturally explain close to maximal mixing if approximate horizontal symmetries force a pseudo-Dirac structure on the neutrino mass matrix. An experimental determination of |ε₁₂| and sign(ε₁₂) can constrain the structure of the lepton mass matrices and consequently provide stringent tests of such flavor models. If both |ε₁₂| and Δm²₂₁ are known, it may be possible to estimate the mass scale of the pseudo-Dirac neutrinos. Radiative corrections to close to maximal mixing are negligible. Subtleties related to the kinetic terms in Froggatt-Nielsen models are clarified.