Measurement of the hadronic cross-section for the scattering of two virtual photons at LEP

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 roots(ec) = 189-209 GeV, for W > 5 GeV and at an average Q(2) of 17.9 GeV(2). The measured cross-sections are compared to predictions of the Quark Parton Model (QPM), to the Leading Order QCD Monte Carlo model PHOJET, to the NLO prediction for the reaction e(+)e(-) --> e(+)e(-) q (q) over bar, and to BFKL calculations. PHOJET, NLO e(+)e(-) --> e(+)e(-) q (q) over bar, and QPM describe the data reasonably well, whereas the cross-section predicted by a Leading Order BFKL calculation is too large.