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 tan β ≃ m t /m b. It also predicts an essentially stable proton, and contains both 'cold' and 'hot' 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 'heavy' charge ±e/6 (colored) and ±e/2 (color singlet) states.