A simple approximation of the one-loop corrected cross section for e+e− → W+W− at LEP 2

Using the SU(2) gauge coupling, gW± (MW±2), at the high-energy scale of MW±, defined by the (theoretical value of the) leptonic W-width, rather than using the low-energy value, defined via the Fermi coupling, Gμ, in the Born approximation, and supplementing with Coulomb corrections and initial state radiation, errors with respect to the exact one-loop results for the differential cross section of e+e− → W+W− are below 1% at LEP 2 energies at all W+W− production angles. A similar procedure is suggested to incorporate leading bosonic loop effects into four-fermion production in the fermion-loop scheme. The resulting accuracy below 1% is sufficient for LEP 2 experiments.