Tests of the Standard Model with Lepton Pair Production Ine + E ? Reactions

The differential cross section of the reactione+e−→e+e− at a c.m. energy of 34.7 GeV has been measured. The result, together with our previously measurede+e−→α+α− data, are compared with the standard model predictions. We obtain for the weak neutral current couplings the valuesg v 2 =0.09×0.06,g a 2 =0.38×0.08. A fit of the Weinberg mixing angle gives the valueg v 2 =0.09×0.06,g a 2 =0.038×0.08. The data are also used to set limits on possible deviations from the pointlike structure of leptons. An upper limit for thee+e− coupling to a heavy spin 0 boson is also given.