Baryon and lepton nonconservation in supersymmetric models

The possible baryon- and lepton-nonconserving effective interactions among ordinary particles are analysed in the frame of SU 3×SU2×U1supersymmetric models. Operators of lower dimensionalities than in ordinary GUTs are generally allowed in the supersymmetric schemes of Dimopoulos and Georgi type, in which a discrete symmetry is imposed to guarantee B and L conservation in renormalizable terms. Operators of the same dimensionalities as in GUTs are obtained, instead, in the schemes of the type considered by Weinberg and by Sakai and Yanagida, where either R-invariance or an extra U 1 gauge factor is assumed. However, the different terms lead in most cases, with the exception of the ΔB=ΔL proton decay, to unobservable rates for physical processes, unless Higgs supermultiplets are introduced at an intermediate mass scale. © 1982 Società Italiana di Fisica.