Constraints on baryon-nonconserving Yukawa couplings in a supersymmetric theory.

The 1-loop evolution of couplings in the minimal supersymmetric standard model, extended to include baryon nonconserving (B/) operators through explicit R-parity violation, is considered keeping only B/ superpotential terms involving the maximum possible number of third generation superfields. If all retained Yukawa couplings Yi are required to remain in the perturbative domain (Yi < 1) upto the scale of gauge group unification, upper bounds ensue on the magnitudes of the B/ coupling strengths at the supersymmetry breaking scale, independent of the model of unification. They turn out to be similar to the corresponding fixed point values reached from a wide range of Yi (including all Yi greater than unity) at the unification scale. The coupled evolution of the top and B/ Yukawa couplings results in a reduction of the fixed point value of the former. Address after 1st October 1994: High Energy Section, International Center For Theoretical Physics, P.O. Box 586, 34100 Trieste, Italy.