$R_b$ in supergravity models

Abstract

We compute the supersymmetric contribution to $R_{b}\equiv Γ(Z\to b{\bar b})/Γ(Z\to {\rm hadrons})$ in a variety of supergravity models. We find $R^{\rm susy}_b\lsim0.0004$, which does not shift significantly the Standard Model prediction ($R^{\rm SM}_b=0.2162$ for $m_t=160\GeV$). An improvement in experimental precision by a factor of four would be required to be sensitive to such an effect.

5 pages, LaTeX, 1 figure (included).