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Small Dirac neutrino masses in supersymmetric grand unified theories

A simple mechanism to generate Dirac masses for the neutrinos in SU(5) supersymmetric grand unified theory is proposed. The tiny Dirac masses are induced by the small mixing between the Higgs fields and another superheavy fields. The mixing terms are obtained by the same mechanism as the mu-term generation of the order of the supersymmetry breaking scale, so that the mixing of order TeV / M_GUT \sim 10^{-13} is realized. We consider the lepton flavor violating processes in this model. The branching ratios are directly related to the neutrino oscillation parameters and we can predict the B(τ-> μγ) / B(μ-> e γ) ratio once the neutrino oscillation parameters are determined.