R symmetry in the minimal supersymmetric standard model and beyond with several consequences

The supersymmetric sector of the minimal supersymmetric standard model possesses a U(1) R symmetry which contains Z{sub 2} matter parity. Nonzero neutrino masses, consistent with a {open_quotes}redefined{close_quotes} R symmetry, are possible through the seesaw mechanism and/or a pair of superheavy (mass M) SU(2){sub L} triplets with a VEV{approximately}M{sub W}{sup 2}/M. If this R symmetry is respected by the higher order terms, then baryon number conservation follows as an immediate consequence. In the presence of right-handed neutrinos, the observed baryon asymmetry of the universe arises via leptogenesis. An interplay of R and Peccei-Quinn symmetry simultaneously resolves the strong CP and {mu} problems. {copyright} {ital 1998} {ital The American Physical Society}