Z→bb¯inU(1)Rsymmetric supersymmetry

We compute the one-loop corrections to the $Z\to b\overline{b}$ vertex in the $\mathrm{U}{\mathrm{}\left(1\right)\mathrm{}}_R$ symmetric minimal supersymmetric extension of the standard model. We find that the predicted value of $R_b$ is consistent with the experimental value if the mass of the lighter top squark is no more than 180 GeV. Furthermore, other data combine to place a lower bound of 88 GeV on the mass of the light top squark. A top squark in this mass range should be accessible to searches by experiments at Fermilab and at CERN LEP.