R-PARITY IN STANDARD-LIKE SUPERSTRING MODELS

Abstract

We investigate the R symmetries of standard-like superstring models. At the level of the cubic superpotential there are three global U(1) R symmetries. These are broken explicitly by N>3 terms in the superpotential and spontaneously by scalar vevs necessary to preserve supersymmetry at Mp. A Z2 discrete symmetry remains but is equivalent to fermion number modulo 2. These models possess an effective R-parity which arises from the interplay between the gauged U(1)B-L and U(1)r i+3.