Effective rank-five superstring models from CP₃×CP₃

We consider three-generation, rank-six superstring models based on the simplest known Calabi-Yau space. Assuming a breaking scale (to rank-five) M_B≳10¹⁶ GeV, as required by cosmology and other constraints, we describe the particle spectrum in a class of models in which the proton is stable and the neutrinos are massless. These models are effectively rank-five down to the weak scale O(100) GeV. We find that Higgs fields typically will have massess in excess of O(10⁶) GeV due to higher order non-renormalizable interactions, hence rendering the conventional spontaneous breakdown of the electroweak symmetries impossible.