Large mixing angle MSW solution in U(1) flavor symmetry

We have discussed the quark–lepton mass matrices with the U(1) flavor symmetry in SU(5), which lead to the large mixing-angle MSW solution of solar neutrinos. The solar-neutrino solution depends on the next-leading terms in the neutrino mass matrix. We have found the lepton mass matrices with the U(1)×Z2 symmetry, which give the LMA-MSW solution uniquely. The coefficients of the matrix elements of the charged leptons are constrained strongly due to the bound of Ue3 in the CHOOZ experiment.