Electroweak Effects ine+e−→μ+μ−at 29 GeV

Abstract

A measurement of the cross section for production of collinear muon pairs based upon a sample of about 3000 events observed in the MAC detector at the storage ring PEP is presented. From the angular asymmetry $A_{\mu \mu }=0.076\mathrm{}\pm 0.018$ the axial-vector weak neutral coupling is found to be given by ${g_A}^e{g_A}^{\mu }=0.31\mathrm{}\pm 0.08$.