Measurement of the forward-backward asymmetry of b and c quark at the Z peak

The forward-backward asymmetries of the processes e/sup +/e/sup -/ to Z to bb and e/sup +/e/sup -/ to Z to cc were measured from a sample of hadronic Z decays collected by the DELPHI experiment between 1993 and 1995. Enriched samples of bb and cc events were obtained using lifetime information. The tagging of b and c quarks in these samples was based on the semileptonic decay channels b/c to X+ mu and b/c to X+e combined with the charge flow information in the hemisphere opposite to the lepton. Averaging the results presented in this paper with those already published with 1991 and 1992 DELPHI data sample, the following pole asymmetries were obtained : A/sub FB//sup 0, b /=0.1013+or-0.0053 (stat.)+or-0.0023 (syst.) A/sub FB//sup 0, c /=0.0735+or-0.0086 (stat.)+or-0.0062 (syst.). (5 refs).