Gauge Coupling Unification in Superstring Derived Standard--like Models

Abstract

I discuss gauge coupling unification in a class of superstring standard--like models, which are derived in the free fermionic formulation. Recent calculations indicate that the superstring unification scale is at $O(10^{18}GeV)$ while the minimal supersymmetric standard model is consistent with LEP data if the unification scale is at $O(10^{16})GeV$. A generic feature of the superstring standard--like models is the appearance of extra color triplets $(D,{\bar D})$, and electroweak doublets $(\ell,{\bar\ell})$, in vector--like representations, beyond the minimal supersymmetric standard model. I show that gauge coupling unification at $O(10^{18}GeV)$ in the superstring standard--like models can be consistent with LEP data. I present an explicit standard--like model that can realize superstring gauge coupling unification.