Precision measurement of the total cross section fore+e−→hadrons at a center-of-mass energy of 29 GeV

We report a high-precision measurement of the ratio R of the total cross section for e/sup +/e/sup -/..-->..hadrons to that for e/sup +/e/sup -/..--> mu../sup +/..mu../sup -/, at a center-of-mass energy of 29.0 GeV using the MAC detector. The result is R = 3.96 +- 0.09. This value of R is used to determine a value of the strong coupling constant ..cap alpha../sub s/ of 0.23 +- 0.06, nearly independent of fragmentation models. Two different analysis methods having quite different event-selection criteria have been used and the results are in agreement. Particular attention has been given to the study of systematic errors. New higher-order QED calculations are used for the luminosity determination and the acceptance for hadrons.