A High-precision Study Of The $z\sp0$ Resonance At Opal (z Boson, Electroweek Standard Model)

The subject of this dissertation is the measurement of the properties of the Z<super>0</super> gauge boson made by the OPAL collaboration. The results presented here constitute one of the main goals of the LEP project at CERN: the determination of a few basic parameters of nature, principally the Z<super> 0</super> mass and its total decay width, as well as its couplings to all of its decay products. Thanks to the excellent performance of the LEP accelerator providing high luminosity with low backgrounds and extremely precise energy calibration, to the installation of a high precision small angle Bhabha luminometer: the Silicon-Tungsten detector (SiW), the careful analysis of event selection efficiencies, and to the increase in the theoretical knowledge of higher order corrections, the high precision finally achieved on these measurements allows the most stringent tests of the electroweak Standard Model of particle physics which have yet been made 1ù...