O(NfαL2) Radiative Corrections in Low-Energy Electroweak Processes

Abstract

Of the the three best-measured electroweak observables, α, G μ and M z , the first two are extracted from low-energy processes. Both G μ and M z are now known to an accuracy of about 2 parts in 105 and there is a proposal to improve the measurement of the muon lifetime by a factor of 10 in an experiment at Brookhaven. Yet calculations of electroweak radiative corrections currently do no better than a few parts in 103–104 and therefore cannot exploit to available experimental precision. We report on the calculation of the O(N fα2) corrections to Thomson scattering and the muon lifetime from which α and G μ, respectively, are obtained. The O(N fα2) corrections are expected to be a dominant gauge-invariant subset of 2-loop corrections.