Measurement of the charged multiplicities in b, c and light quark events from Z0 decays

Average charged multiplicities have been measured separately in b, c and light quark (u, d, s) events from Z0 decays measured in the SLD experiment. Impact parameters of charged tracks were used to select enriched samples of b and light quark events, and reconstructed charmed mesons were used to select c quark events. We measured the charged multiplicities: nuds = 20.21 ± 0.10(stat.) ± 0.22(syst.), nc = 21.28 ± 0.46(stat.)−0.36+0.41syst.) and nb = 23.14 ± 0.10(stat.)−0.37+0.38(syst.), from which we derived the differences between the total average charged multiplicities of c or b quark events and light quark events: Δnc = 1.07 ± 0.47(stat.)−0.30+0.36(syst.) and Δnb = 2.93 ± 0.14(stat.)−0.29+0.30(syst.). We compared these measurements with those at lower center-of-mass energies and with perturbative QCD predictions. These combined results are in agreement with the QCD expectations and disfavor the hypothesis of flavor-independent fragmentation.