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

TL;DR

This paper measures the cross-section of virtual photon interactions at LEP energies, comparing experimental data with various theoretical models including QPM, PHOJET, NLO QCD, and BFKL, revealing good agreement with some models and discrepancies with BFKL.

Contribution

First measurement of the hadronic cross-section for virtual photon scattering at LEP energies, with detailed comparison to multiple theoretical predictions.

Findings

PHOJET and NLO QCD models agree well with data.

Leading Order BFKL overestimates the cross-section.

Results support certain QCD models over others.

Abstract

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 sqrt(s_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 e+e- -> e+e-qqbar, and to BFKL calculations. PHOJET, NLO e+e- -> e+e-qqbar, and QPM describe the data reasonably well, whereas the cross-section predicted by a Leading Order BFKL calculation is too large.