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Inclusive production of D\(^{\ast\pm}\) mesons in photon-photon collisions at \(\sqrt{s}_{\rm ee}=183\) and 189 GeV and a first measurement of \(F^\gamma _{2,{\rm c}}\)

  • The OPAL Collaboration
  • G. Abbiendi et al.
Experimental physics

Abstract.

The inclusive production of \({{\rm D}^{\ast\pm}}\) mesons in photon-photon collisions has been measured using the OPAL detector at LEP at \(\mboxe^+\mboxe^-\) centre-of-mass energies \(\sqrt{s_{\rm ee}}\) of 183 and 189 GeV. The \({{\rm D}^{\ast+}}\) mesons are reconstructed in their decay to \({\rm D}^0\pi^+\) with the \({\rm D}^0\) observed in the two decay modes \({\rm K}^-\pi^+\) and \({\rm K}^-\pi^+\pi^-\pi^+\). After background subtraction, \(100.4\pm12.6 (\rm stat)\)\({\rm D}^{\ast\pm}\) mesons have been selected in events without observed scattered beam electron (“anti-tagged”) and \(29.8 \pm 5.9 ({\rm stat}){{\rm D}^{\ast\pm}}\) 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 \({\rm d}\sigma/{\rm d}p_{\rm T}^{{\rm D}^{\ast}}\) and \({\rm d} \sigma/{\rm d} \vert \eta^{{\rm D^{\ast}}}\vert\) as functions of the \({{\rm D}^{\ast\pm}}\) transverse momentum \(p^{\rm D^{\ast}}_{\rm T}\) and pseudorapidity \(\eta^{{\rm D}^{\ast}}\) are presented in the kinematic region \(2{\rm GeV} < p^{\rm D^{\ast}}_{\rm T} < 12{\rm GeV}\) and \(|\eta^{{\rm D}^{\ast}}|< 1.5\). They are compared to next-to-leading order (NLO) perturbative QCD calculations. The total cross-section for the process \(\mboxe^+\mboxe^- \to \mboxe^+\mboxe^- \mbox c\overline{\mbox c}\) where the charm quarks are produced in the collision of two quasi-real photons is measured to be \(\sigma({\rm e}^+{\rm e}^- \to{\rm e}^+{\rm e}^-{\rm c}\bar{{\rm c}}) = 963\pm 110 ({\rm stat})\pm 86({\rm sys})\pm 224 ({\rm extrapolation}){\rm pb}\). A first measurement of the charm structure function \(F^\gamma _{2,{\rm c}}\) of the photon is performed in the kinematic range \(0.0014 < x < 0.87\) and \(5 {\rm GeV}^2 < Q^2 < 100{\rm GeV}^2\), and the result is compared to a NLO perturbative QCD calculation.

Keywords

Beam Electron Transverse Momentum Structure Function Opal Detector Decay Mode 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • The OPAL Collaboration
  • G. Abbiendi et al.
    • 1
  1. 1.Dipartimento di Fisica dell' Università di Bologna and INFN, 40126 Bologna, ItalyIT

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