$R_b$ in supergravity models

Abstract

We compute the supersymmetric contribution to $R_b\equiv \Gamma (Z\to b\bar{b})/\Gamma (Z\to \mathrm{hadrons})$ in a variety of supergravity models. We find $R_b^{\mathrm{susy}}\text{lsim}0.0004$, which does not shift significantly the Standard Model prediction ($R_b^{\mathrm{SM}}=0.2162$ for $m_t=160\text{GeV}$). An improvement in experimental precision by a factor of four would be required to be sensitive to such an effect.

Comments: 5 pages, LaTeX, 1 figure (included).