Heterotic road to the MSSM withRparity

Abstract

In a previous paper, referred to as a ``Mini-Landscape'' search, we explored a ``fertile patch'' of the heterotic landscape based on a ${\mathbb{Z}}_{6}\ensuremath{-}\mathrm{II}$ orbifold with SO(10) and ${\mathrm{E}}_{6}$ local grand unified theory structures. In the present paper we extend this analysis. We find many models with the minimal supersymmetric standard model spectra and an exact $R$ parity. In all of these models, the vectorlike exotics decouple along $D$-flat directions. We present two benchmark models which satisfy many of the constraints of a realistic supersymmetric model, including nontrivial Yukawa matrices for three families of quarks and leptons and Majorana masses for right-handed neutrinos with nontrivial seesaw masses for the three light neutrinos. In an appendix we comment on the important issue of string selection rules and, in particular, the so-called ``gamma-rule''.