Supersymmetry and large scale left-right symmetry

We show that the low energy limit of the minimal supersymmetric left-right models is the supersymmetric standard model with an exact R parity. The theory predicts a number of light Higgs scalars and fermions with masses much below the B-L and SU(2)_R breaking scales. The nonrenormalizable version of the theory has a striking prediction of light doubly charged supermultiplets which may be accessible to experiment. Whereas in the renormalizable case the scale of parity breaking is undetermined, in the nonrenormalizable one it must be bigger than about 10¹⁰-10¹² GeV. The precise nature of the seesaw mechanism differs in the two versions, and has important implications for neutrino masses.