Minimal supersymmetric SU(4)×SU(2)L×SU(2)R

We present a minimal string-inspired supersymmetric SU(4)×SU(2)L×SU(2)R model, and provide a detailed analysis of the symmetry breaking potential in this model, based on a generalisation of that recently proposed by Dvali, Lazarides and Shafi. The model contains a global U(1) R-symmetry and reduces to the MSSM at low energies. However it improves on the MSSM since it explains the magnitude of its μ term and gives a prediction for tanβ≃mt/mb. It also predicts an essentially stable proton, and contains both `coldʹ and `hotʹ dark matter candidates. A period of hybrid inflation above the symmetry breaking scale is also possible in this model. Finally it suggests the existence of `heavyʹ charge ±e/6 (colored) and ±e/2 (color singlet) states.