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 \({\rm e^+e^-} \rightarrow{\rm e^+e^-}\) hadrons based on data taken by the OPAL experiment at \({\rm e^+e^-}\) centre-of-mass energies \(\sqrt{s_{\rm ee}}=189-209\) 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 \({\rm e^+e^-}\rightarrow{\rm e^+e^-} q\bar{q}\), and to BFKL calculations. PHOJET, NLO \({\rm e^+e^-}\rightarrow{\rm e^+e^-} q\bar{q}\), and QPM describe the data reasonably well, whereas the cross-section predicted by a Leading Order BFKL calculation is too large.