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 ( Lambda(QCD)/Q)(n) to the total cross section may become non-negligible . Based on a dispersion relation for the running coupling, we discuss these contributions and calculate the coefficients of the leading powe r correction for transversely polarized and longitudinally polarized v irtual photons.