Investigation of the two-photon production of D*-mesons with the ALEPH detector at LEP

The inclusive production of D∗± mesons in two-photon collisions has been measured with the ALEPH detector at center-of-mass energies in the range √s = 183 − 189 GeV. D∗+ mesons are reconstructed in the decay D∗+ → D0π+ and the D0’s in turn are identified in the decay channels (i) K−π+, (ii) K−π+π0, and (iii) K−π+π−π+, and analogously for D∗− modes. A total number of 113 ± 15 D∗ events was observed from an integrated luminosity of L = 23 6.3pb−1. Contributions from direct and single resolved processes have been separated using event shape variables. Differential cross sections of D∗ production as a function of the transverse momentum pD∗ t and of the pseudorapidity ηD∗ of the D∗ meson have been measured in the range 2 GeV < pD∗ t < 12 GeV and |ηD∗ | < 1.5 and have been compared to NLO calculations as well as to an OPAL measurement. An extrapolation of the integrated visible D∗ cross section to the total charm cross section has been performed using predictions of the Pythia Monte Carlo program as well as predictions from a NLO calculation which show significant deviations.