We have measured the process $e^{+}$$e^{\mathrm{-}}$→${\mu }^{+}$${\mu }^{\mathrm{-}}$ at √s =29 GeV using the High Resolution Spectrometer at SLAC PEP. The forward-backward charge asymmetry is $A_{\mu \mu }$=-(4.9±1.5±0.5)% based on 5057 events. A subsample of 3488 ${\mu }^{+}$${\mu }^{\mathrm{-}}$ events in the angular range ‖cosθ‖<0.55 gives a cross-section ratio of $R_{\mu \mu }$=0.990±0.017±0.030. The resulting couplings of the weak neutral current are $g_a^e$$g_a^{\mu }$=0.208±0.064± 0.021 and $g_v^e$$g_v^{\mu }$=0.027 ±0.051±0.089. The QED cutoff parameters are ${\Lambda }_{+}$>170 GeV and ${\Lambda }_{\mathrm{-}}$>146 GeV at 95% C.L.

• Received 25 October 1984

DOI:https://doi.org/10.1103/PhysRevD.31.2352