TTP99-18 On the Precise Determination of the Fermi Coupling Constant from the Muon Lifetime

The determination of the Fermi coupling constant, G_F, is examined in the light of recently calculated 2-loop QED corrections and planned experiments tomeasure the muon lifetime to a level below 1ppm. The methods used in the calculation of the QED corrections are described in detail. Sources of thedominant theoretical and experimental uncertainties are identified. Finally the incorporation of G_F into analyses using the full electroweak Standard Model is discussed.