Measurement of the Hadronic Cross-Section for the Scattering of Two Virtual Photons at Opal

The interaction of virtual photons is investigated using the reaction e⁺e^- → e⁺e^- hadrons based on data taken by the OPAL experiment at e⁺e^- centre-of-mass energies √ {s_ee} = 189-209\ GeV, for W > 5 GeV and at an average Q² of 17.9 GeV². The measured cross sections are compared to the predictions of the Quark Parton Model (QPM), to the leading order (LO) QCD Monte Carlo model PHOJET, to the NLO prediction for the reaction e⁺e^- -> e⁺e^-qbar {q}, and to BFKL calculations. PHOJET, NLO e⁺e^- -> e⁺e^-qbar {q}, QPM describe the data reasonably well, whereas the cross section predicted by a LO BFKL calculation is too large.