TEST OF QED IN e+ e- ANNIHILATION AT ENERGIES BETWEEN 12-GeV AND 31.6-GeV

We have measured the reactions e+e− → e+e− → μ+μ− and e+e− → γγ at c.m. energies between 12 and 31.6 GeV. Excellent agreement with the predictions of QED has been found, resulting in cut off parameters Λ+ > 112 GeV and Λ− > 139 GeV for the first process and Λ+ > 34 GeV and Λ− > 42 GeV (95% c.1.) for the last one. A limit on the Weinberg angle of sin2θW < 0.55 (95% c.1.) has been obtained