Constraints on baryon-nonconserving Yukawa couplings in a supersymmetric theory

The one-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 ${\mathit{Y}}_{\mathit{i}}$ are required to remain in the perturbative domain (${\mathit{Y}}_{\mathit{i}}$<1) up to 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 ${\mathit{Y}}_{\mathit{i}}$ (including all ${\mathit{Y}}_{\mathit{i}}$ greater than unity) at the unification scale. The coupled evolution of the top quark and B/ Yukawa couplings results in a reduction of the fixed point value of the former.