Measurement of the inclusive D$^{*\pm}$ production in $\gamma\gamma$ collisions at LEP

Abstract.

The inclusive production of D$^{*\pm}$ mesons in two-photon collisions is measured with the ALEPH detector at e⁺e^- centre-of-mass energies from 183 GeV to 209 GeV. A total of $360 \pm 27$ D$^{*\pm}$ meson events are observed from an integrated luminosity of 699pb^-1. Contributions from direct and single-resolved processes are separated using the ratio of the transverse momentum $p_{t}^{D^{*\pm}}$ of the D$^{*\pm}$ to the visible invariant mass W_vis of the event. Differential cross sections of D$^{*\pm}$ production as functions of $p_{t}^{D^{*\pm}}$ and the pseudorapidity $\vert\eta^{D^{*\pm}}\vert$ are measured in the range 2 GeV$/c < p_{t}^{D^{*\pm}} < 12$ GeV/c and $\vert\eta^{D^{*\pm}}\vert < 1.5$. They are compared to next-to-leading order (NLO) perturbative QCD calculations. The extrapolation of the integrated visible D$^{*\pm}$ cross section to the total charm cross section, based on the Pythia Monte Carlo program, yields $\sigma (e^+e^- \rightarrow e^+e^- c\bar{c})_{\left<\sqrt{s}\right> = 197 GeV} = 731 \pm 74_{stat} \pm 47_{syst} \pm 157_{extr}$pb .