Measurements of the Running of the Electromagnetic Coupling at LEP

Abstract

The study of Bhabha scattering at e^+e^- colliders probes the running of the electromagnetic coupling. After early measurements by the VENUS collaboration at TRISTAN and the by L3 collaboration at LEP, two recent analyses have been performed by the OPAL and L3 collaborations. The OPAL collaboration studied high-statistics low-angle Bhabha scattering at LEP, achieving a precise determination of the running of alpha in the region 1.8GeV^2<-Q^2<6.1GeV^2. The L3 collaboration investigated high-energy large-angle Bhabha scattering to first probe the region 1800GeV^2 < -Q^2 < 21600GeV^2. All measurements are described and a global overview of their agreement with QED predictions is given.