Coupling strengths of weak neutral currents from leptonic final states at 22 and 34 GeV

Differential cross sections for e+e-→e+e-, μ+μ-, tau+tau- measured with the CELLO detector at <√s>=34.2 GeV have been analyzed for electroweak contributions. Vector and axial vector coupling constants were obtained in a simultaneous fit to the three differential cross sections assuming a universal weak interaction for the charged leptons. The results, ν2=-0.12+-0.33 and a2=1.22+-0.47, are in good agreement with predictions from the standard SU(2)xU(1) model for sin2Osub(w)=0.228. Combining this result with neutrino-electron scattering data gives a unique axial vector dominated solution for the leptonic weak couplings. Assuming the validity of the standard model, a value of sin2THETAsub(w)=0.21sub(-0.09)sup(+0.14) is obtained for the electroweak mixing angle. Additional vector currents are not observed (C<0.031 is obtained at the 95% C.L.). (orig.)