We propose a new possibility to realize simultaneously the sufficient proton
stability and the interesting structure of neutrino mass matrix in superstring
inspired E6β models. In this model the leptons and Higgs fields are assigned
to a fundamental representation {\bf 27} in the different way among
generations. Two pairs of Higgs doublets naturally remain light from three
generation ones by imposing certain discrete symmetries, although all extra
color triplets become sufficiently heavy. Under these symmetries suitable
ΞΌ-terms to bring appropriate vacuum expectation values are prepared and the
dangerous FCNC is avoidable. Some related phenomena to this model, especially,
the structure of neutrino mass matrix are also discussed.Comment: 20 pages, latex, a version published in Prog. Theor. Phys.,
discussions related to neutrino masses are change