Inclusive production of D*+- mesons in photon-photon collisions at sqrt(s) = 183 and 189 GeV and a first measurement of the the charm structure function of the photon

TL;DR

This paper reports on the measurement of D*+- meson production in photon-photon collisions at LEP energies, providing insights into charm quark production and the photon’s charm structure function, with results compared to NLO QCD predictions.

Contribution

It presents the first measurement of the charm structure function of the photon and compares experimental data with NLO QCD calculations.

Findings

Measured total charm production cross-section: 842+-97 pb.

First determination of the photon charm structure function F2.

Differential cross-sections align with NLO QCD within uncertainties.

Abstract

The inclusive production of D*+- mesons in photon-photon collisions has been measured using the OPAL detector at LEP at e+e- centre-of-mass energies of 183 and 189GeV. The D* mesons are reconstructed in their decay to D0pi+ with the D0 observed in the two decay modes Kpi+ and Kpi+pi-pi+. After background subtraction, 100.4+-12.6(stat) D*+- mesons have been selected in events without observed scattered beam electron ("anti-tagged") and 29.8+-5.9 (stat) D*+- mesons in events where one beam electron is scattered into the detector ("single-tagged"). Direct and single-resolved events are studied separately. Differential cross-sections as functions of the D* transverse momentum p_t and pseudorapidity \eta are presented in the kinematic region 2<p_t<12GeV and \eta<1.5. They are compared to next-to-leading order (NLO) perturbative QCD calculations. The total cross-section for the process (e+e- to e+e-ccbar), where the charm quarks are produced in the collision of two quasi-real photons, is measured to be 842+-97(stat)+-75(syst)+-196(extrapolation)pb. A first measurement of the charm structure function F2 of the photon is performed in the kinematic range 0.0014<x<0.87 and 5<Q^2<100 GeV^2, and the result is compared to a NLO perturbative QCD calculation.