Test of the electroweak interaction in the reaction e+e- → μ+μ-

The reaction e+e- → μ+μ- has been studied with the MARK J detector at the PETRA storage ring at c.m. energies of 14-46.78 GeV. The measured characteristic quantities of the muon pair production, the total cross section and the charge asymmetry show a very good agreement with the standard model of the electroweak interaction. Nearly 10000 observed events are available for the analysis. From this purely leptonic process values for the electroweak parameters, the weak mixing angle θW and the mass of the Z0 boson mZ: sin2θW = 0.19(+0.04-0.02)±0.01 and mZ = (89(+4-3)±1) GeV. These values possess only low experimental and theoretical uncertainties. They are in very good agreement with other results from the e+e- annihilation and the results derived from other physical processes. For the vector and axial-vector coupling constant of electron and muon in this experiment the following values have been determined: vertical strokegvvertical stroke = 0.21(+0.10-0.21) and vertical strokegavertical stroke = 0.52±0.02. The ρ parameter could from the measured charge asymmetry be determined to ρ = 1.09±0.10±0.03. A special regard of this thesis lies on the experimental test of the radiative corrections up to including the order α3 on the asymmetry. The excellent directional resolution of the MARK J detector for muons allows the study of the charge asymmetry as function of the polar-angle difference also for very small angles. By this the separation of bremsstrahlung diagrams and other corrections is reached so that its specific influence on the asymmetry can be measured. The theoretical predictions could be verified in the experiment. (orig.)