Supersymmetric Left-Right Model, Automatic R-parity Conservation and   Constraints on the $W_R$ Mass
  Supersymmetric left-right models with the see-saw mechanism for the neutrino masses have the attractive property that they conserve baryon and lepton number exactly in the Lagrangian. In this talk, I review the recent results valid for a large class of minimal versions of the model that supersymmetry combined with the requirement that the ground state of the model conserve electric charge constrains the mass of the right handed $W_R$ boson to be in a certain range i.e. $M_{W_R}\leq$ 10 TeV or $\geq 10^{10}$ GeV. In the former case (low $M_{W_R}$), the vacuum breaks R-parity spontaneously and the latter case (high $M_{W_R}$) is required if vacuum is to conserve R-parity. In the second case, the effective low energy theory is the MSSM with exact R-parity, nonvanishing neutrino masses and a pair of light doubly charged Higgs fields and their fermionic partners. Exact R-parity conservation via see saw mechanism therefore implies that the neutrino masses must be in the desired range to solve the solar and atmospheric neutrino puzzles. 
R. N. Mohapatra