Measurement of the Hadronic Photon Structure Function F2gamma at LEP2

TL;DR

This paper measures the photon structure function F2gamma at LEP2 across various x and Q2 values, confirming QCD predictions of positive scaling violations and comparing different theoretical models with experimental data.

Contribution

It extends previous measurements of F2gamma to higher Q2 and provides detailed analysis of its Q2 evolution and x dependence at LEP2 energies.

Findings

F2gamma increases with Q2 in the central x region, confirming positive scaling violations.

Several parameterisations agree qualitatively with data, but quark-parton model predictions do not.

Measurement covers a broad kinematic range, improving understanding of photon structure.

Abstract

The hadronic structure of the photon F2gamma is measured as a function of Bjorken x and of the photon virtuality Q2 using deep-inelastic scattering data taken by the OPAL detector at LEP at e+e- centre-of-mass energies from 183 to 209 GeV. Previous OPAL measurements of the x dependence of F2gamma are extended to an average Q2 of <Q2>=780GeV2 using data in the kinematic range 0.15 < x < 0.98. The Q2 evolution of F2gamma is studied for 12.1 < <Q2> < 780GeV2 using three ranges of x. As predicted by QCD, the data show positive scaling violations in F2gamma for the central x region 0.10-0.60. Several parameterisations of F2gamma are in qualitative agreement with the measurements whereas the quark-parton model prediction fails to describe the data.