LARGE LEPTON FLAVOR MIXING AND E-6-TYPE UNIFICATION MODELS

There are experimental indications of large flavor mixing between nu(m u) and nu(tau). In the unification models, in which the massless secto r includes extra particles beyond the standard model, there possibly a ppear mixings between quarks (leptons) and extra particles. When large mixings occur, lepton flavor mixings can be quite different from quar k flavor mixings. By studying the string inspired SU(6) x SU(2)(R) mod el with global flavor symmetries, we obtain the neutrino flavor mixing sin theta(23) similar or equal to lambda = sin theta(C) up to renorma lization effects. It can be expected that due to large Yukawa coupling s of the third generation, the renormalization effect increases sin2 t heta(23) naturally up to similar to 1 at the electroweak scale. The fe rmion mass spectra and the CKM matrix of quarks obtained in this paper are also phenomenologically viable.