Electroweak Precision Tests ∗

The Standard Model (SM) constitutes one of the most successful achievements in modern physics. It provides a very elegant theoretical framework, which is able to describe all known experimental facts in particle physics. A detailed description of the SM and its impressive phenomenological success can be found in Refs. [1] and [2], which discuss the electroweak and strong sectors, respectively. The high accuracy achieved by the most recent experiments allows to make stringent tests of the SM structure at the level of quantum corrections. The different measurements complement each other in their different sensitivity to the SM parameters. Confronting these measurements with the theoretical predictions, one can check the internal consistency of the SM framework and determine its parameters. The following sections provide an overview of our present experimental knowledge on the electroweak couplings. A brief description of some classical QED tests is presented in Section 2. The leptonic couplings of the W± bosons are analyzed in Section 3, where the tests on lepton universality and the Lorentz structure of the l− → νll′−ν̄l′ transition amplitudes are discussed. Section 4 describes the status of the neutral–current sector, using the latest experimental results reported by LEP and SLD. Some summarizing comments are finally given in Section 5.