The ratio $R$ of the total cross section for ${e}^{+}{e}^{\ensuremath{-}}$ annihilation into hadrons to the lowest-order QED cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ 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.
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