ON THE OBSERVATION OF BOSONIC LOOP CORRECTIONS IN ELECTROWEAK PRECISION EXPERIMENTS

We investigate the structure of the experimentally significant electro weak bosonic loop corrections to the leptonic weak mixing angle, the l eptonic Z-boson decay width, and the W-boson mass. It is shown that th e bosonic corrections that have a sizable effect at the present level of experimental accuracy are directly related to the use of the Fermi constant G(mu) as input parameter for analyzing the LEP observables. I ndeed, if the (theoretical value of the) leptonic width of the W boson is used as input parameter instead of the low-energy parameter G(mu) determined from muon decay, fermion-loop corrections are sufficient fo r compatibility between theory and experiment.