SO(10)-like Superstring Standard Model with R-parity from the Heterotic String

We construct a supersymmetric standard model in the context of the Z12−I orbifold compactification of the E8 × E ′ 8 heterotic string theory. The gauge group is SU(3)c × SU(2)L × U(1)Y ×U(1) 4 × [SO(10)× U(1)] with sinθ W = 3/8. We obtain three families of SO(10) spinor-like chiral matter states, and Higgs doublets. All other extra states are exactly vector-like under the standard model gauge symmetry. There are numerous standard model singlets, many of which get VEVs such that only the standard model gauge symmetry survives and desired Yukawa couplings can be generated at lower energies. In particular, all vector-like exotic states achieve superheavy masses and the R-parity can be preserved. PACS. 11.25.Mj Compactification and four-dimensional models