Measurement of the hadronic photon structure function F₂γ at LEP2

The hadronic structure function of the photon F-2(gamma) (x, Q(2)) is measured as a function of Bjorken x and of the photon virtuality Q(2) 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 F-2(gamma) are extended to an average Q(2) of = 780 GeV2 using data in the kinematic range 0.15 <x <0.98. The Q(2) evolution of F-2(gamma) is studied for 12.1 <<Q(2)> <780 GeV2 using three ranges of x. As predicted by QCD, the data show positive scaling violations in F-2(gamma) with F-2(gamma) (Q(2))/alpha = (0.08 +/- 0.02(-0.03)(+0.05)) + (0.13 +/- 0.01(-0.01)(+0.01)) In Q(2), where Q(2) is in GeV2, for the central x region 0.10-0.60. Several parameterisations of F-2(gamma) are in qualitative agreement with the measurements whereas the quark-parton model prediction fails to describe the data. (C) 2002 Elsevier Science B.V. All rights reserved.