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

Abstract Average charged multiplicities have been measured separately in b , c and light quark ( u , d , s ) events from Z 0 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: n uds = 20.21 ± 0.10( stat. ) ± 0.22( syst. ) , n c = 21.28 ± 0.46( stat. ) −0.36 +0.41 syst. ) and n b = 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: Δ n c = 1.07 ± 0.47( stat. ) −0.30 +0.36 ( syst. ) and Δ n b = 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.