A NEW STRING-INSPIRED STANDARD MODEL (SISM)

The unification of gauge couplings in string models is predicted to occur at scales (approximately 10(18) GeV) which are in disagreement with those obtained, using precise LEP data, in supersymmetric models with minimal matter content (approximately 10(16) GeV). We present a string-inspired extension of the standard model with one pair of extra vector-like Q and D(c) representations which allows string unification for D(c) masses in the few TeV region or less, predicts a light (< 1 TeV) sparticle spectrum which differs from that of the standard supersymmetric model, and allows for adequate radiative electroweak symmetry breaking. The proposed model is the unique minimal choice in this class of extra vector models, it can be embedded most economically in a flipped SU(5) structure, and may be derivable from string.