FERMION MASSES AND MIXINGS IN A STRING INSPIRED MODEL

In the context of Calabi-Yau string models we explore the origin of ch aracteristic pattern of quark-lepton masses and the CKM matrix. The di screte R-symmetry Z(K)xZ(2) is introduced, and the Z(2) is assigned to the R-parity. The gauge symmetry at the string scale, SU(6) x SU(2)(R ), is broken into the standard model gauge group at a Very large inter mediate energy scale. At energies below the intermediate scale down-ty pe quarks and also leptons are mixed with unobserved heavy states, res pectively. On the other hand, there are no such mixings for up-type qu arks. Due to the large mixings between light states and heavy ones we can derive phenomenologically viable fermion mass hierarchies and the CKM matrix. Mass spectra for intermediate-scale matter beyond the MSSM are also determined. Within this framework proton lifetime is long en ough to be consistent with experimental data. As for the string scale unification of gauge couplings, however, consistent solutions have not yet been found.