Minimal supersymmetric SU(4)xSU(2)LxSU(2)R

We present a minimal string-inspired supersymmetric SU(4)xSU(2)(L) x 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 mu term and gives a prediction for tan beta similar or equal to(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. (C) 1998 Elsevier Science B.V.