The ratio $R$ of the total cross section for $e^{+}{e}^{-}$ annihilation into hadrons to the lowest-order QED cross section for $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ has been measured for center-of-mass energies ranging from 50 to 61.4 GeV. If we allow for an overall shift of —4.9%, about 1.5 times our estimated normalization error, the results are consistent with the standard-model predictions.

• Received 5 February 1990

DOI:https://doi.org/10.1103/PhysRevD.42.1339