Measurement of the charm structure function F₂,c of the photon at LEP

The production of charm quarks is studied in deep-inelastic electron-photon scattering using data recorded by the OPAL detector at LEP at nominal e(+)e(-) centre-of-mass energies from 183 to 209 GeV. The charm quarks have been identified by full reconstruction of charged D-* mesons using their decays into D(0)pi with the DO observed in two decay modes with charged particle final states, Kpi and Kpipipi. The cross-section or D* for production of charged D-* in the reaction e(+)e(-) --> e(+)e(-)D(*)X is measured in a restricted kinematical region using two bins in Bjorken x, 0.0014 <x <0.1 and 0.1 <x <0.87. From sigma(D*) the charm production cross-section sigma(e(+)e(-) --> e(+)e(-)c (c) over barX) and the charm structure function of the photon F-2,c(gamma) are determined in the region 0.0014 <x <0.87 and 5 <Q(2) <100 GeV2. For x > 0.1 the perturbative QCD calculation at next-to-leading order agrees perfectly with the measured cross-section. For x <0. 1 the measured cross-section is 43.8+/-14.3 6.3+/-2.8 pb with a next-to-leading order prediction of 17.0(-2.3)(+2.9) pb. (C) 2002 Elsevier Science B.V. All rights reserved.