Effective QCD coupling and power corrections to photon-photon scattering

The scattering of two off-shell photons is an infrared-safe process in QCD. For photon virtualities Q in the range of a few GeV, accessible at the CERN e+e- collider LEP II, power-behaved contributions in (ΛQCD/Q)n to the total cross section may become non-negligible. Based on a dispersion relation...