Study of single Z-boson production and Compton scattering in electron-positron collisions at LEP at centre-of-mass energies up to 209 GeV

This thesis discusses two main topics. First, the cross section of the process e + e - [arrow right]Ze + e - is measured with 0.7 ph - of data collected with the L3 detector at LEP. Decays of the Z boson into quarks and muons are considered at center-of-mass energies ranging frond 183 GeV up to 209 GeV. The measurements are found to agree with Standard Model predictions, achieving a precision of about 10% for the hadronic channel. Second, Compton scattering of quasi-real virtual photons, γe ± [arrow right]γe ± , is studied with 0.6 fb - 1 of data collected by the L3 detector at LEP at center-of-mass energies [Special characters omitted.] = 189--209GeV. About 4500 events produced by the interaction of virtual photons emitted by particles of one beam with particles of the opposite beam are collected for effective center-of-mass energies of photon-electron and photon-positron systems in the range [Special characters omitted.] = 35 GeV up to [Special characters omitted.] = 175 GeV, the highest energy at which Compton scattering was ever probed. The cross sections of the γe ± [arrow right]γe ± process as a function of [Special characters omitted.] and the differential cross section with respect to scattering angle, [straight theta]*, are measured and combined with previous L3 measurements down to [Special characters omitted.] ≈ 20 GeV, and found to agree with the QED expectations.