Three-generation superstring models with discrete R symmetries

Abstract

Compactification of the ten-dimensional heterotic E 8×E 8 superstring theory on certain Calabi-Yau manifolds yields three-generation models possessing discrete R symmetries. We consider an example based on Z 2 (ordinary symmetry) × Z 3 (R symmetry) with four-dimensional gauge symmetry SU(3) c × SU(3) L × SU(3) R. We investigate how features such as adequate suppression of proton decay, appearance of a pair of electroweak scale Higgs doublets, and perturbative unification of the standard model gauge couplings at the compactification scale can emerge from such models. Matter parity and R symmetry, especially the latter, which are related to Z 2 and Z 3 respectively, play essential roles in our considerations.