Electroweak effects on the reaction e+e- → μ+μ- at √s = 29 GeV

We have measured the differential cross section for the reaction e+e- → μ+μ- at √s = 29 GeV, using the High Resolution Spectrometer at PEP. From the angular distribution based on 5057 μ+μ- events (total integrated luminosity 106 pb-1), we find the forward-backward charge asymmetry to be A/sub μμ/ = -(4.9 +- 1.5 +- 0.5)%. The first error is statistical and the second systematic. The QED correction up to order α3 included in the above number is +1.6%. The absolute cross section based on the subsample of 3488 μ+μ- events in the angular range -0.55 < cos theta < +0.55 gives a cross section ratio to the QED prediction of R/sub μμ/ = 0.990 +- 0.017 +- 0.030. We measure the axial vector coupling and the vector coupling of the weak neutral current to be g/sub a//sup e/g/sub a//sup μ/ = 0.208 +- 0.064 +- 0.021 and g/sub v//sup e/g/sub v//sup μ/ = 0.027 +- 0.051 +- 0.089, respectively. These numbers are consistent with the standard model