Measurement of muon-pair production with the L3 experiment

This thesis reports on measurements of $\rm e\sp+e\sp-$ annihilation into muon pairs with the L3 detector at LEP. At center-of-mass energies around the Z mass, 16833 muon pairs are selected, corresponding to 23.7 pb$\sp{-1}$ of integrated luminosity. From the data samples taken at center-of-mass energies between 130 GeV and 183 GeV, 692 muon pairs are selected, corresponding to 88.5 pb$\sp{-1}$ of integrated luminosity. The cross section and forward-backward asymmetry measurements, combined with other results on lepton-pair production, are used to determine the mass and width of the Z boson, its couplings to lepton and the $\gamma$Z interference. The results obtained The results of all measurements agree well with the Standard Model predictions.