Measurement of the forward backward asymmetry of c and b quarks at the Z pole using reconstructed D mesons

A measurement of the forward-backward asymmetry of e+e- → cc̄ and e+e- → bb̄ on the Z resonance is performed using about 3.5 million hadronic Z decays collected by the DELPHI detector at LEP in the years 1992 to 1995. The heavy quark is tagged by the exclusive reconstruction of several D meson decay modes. The forward-backward asymmetries for c and b quarks at the Z resonance are determined to be: AcFB(√s = 91.235GeV) = 0.0659 ± 0.0094 (stat) ± 0.0035 (syst) AbFB(√s = 91.235 GeV) = 0.0762 ± 0.0194 (stat) ± 0.0085 (syst) AcFB(√s = 89.434 GeV) = -0.0496 ± 0.0368 (stat) ± 0.0053 (syst) AbFB(√s = 89.434 GeV) = 0.0567 ± 0.0756 (stat) ± 0.0117 (syst) AcFB(√s = 92.990 GeV) = 0.1180 ± 0.0318 (stat) ± 0.0062 (syst) AbFB(√s = 92.990 GeV) = 0.0882 ± 0.0633 (stat) ± 0.0122 (syst) The combination of these results leads to an effective electroweak mixing angle of: sin2 θlepteff = 0.2332 ± 0.0016.