New results on the reactione+e−→Author(s) - M. Derrick, E. Fernández, Rainer J. Fries, L. Hyman, P. Kooijman, J. S. Loos, B. Musgrave, L. E. Price, J. Schlereth, K. Sugano, J. M. Weiss, D. Wood, S. P. Ahlen, G. Baranko, P. Baringer, D. Blockus, B. Brabson, M. Daigo, G. E. Forden, S. W. Gray, J.P. Guillaud, C. K. Jung, H. A. Neal, H. Ogren, D. R. Rust, M. Valdata-Nappi, C. Akerlof, J. Chapman, D. Errede, N. Harnew, P. Kesten, S.A.L.M. Kooijman, D. I. Meyer, D. Nitz, D. Rubin, A. A. Seidl, R. Thun, T. Trinko, M. Willutzky, I. Beltrami, R. DeBonte, K. K. Gan, D. Koltick, F.J. Loeffler, U. Mallik, R. L. McIlwain, D. H. Miller, C. R. Ng, P. P. Ong, L. K. Rangan, E. I. Shibata, R. Stevens, R. J. Wilson, B. Cork, L. Keller, J. Va’vra

We have measured the process e+e-→μ+μ- at s =29 GeV using the High Resolution Spectrometer at SLAC PEP. The forward-backward charge asymmetry is Aμμ=-(4.9±1.5±0.5)% based on 5057 events. A subsample of 3488 μ+μ- events in the angular range cosθ<0.55 gives a cross-section ratio of Rμμ=0.990±0.017±0.030. The resulting couplings of the weak neutral current are gaegaμ=0.208±0.064± 0.021 and gvegvμ=0.027 ±0.051±0.089. The QED cutoff parameters are Λ+>170 GeV and Λ->146 GeV at 95% C.L. © 1985 The American Physical Society