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: ${\bar{n}}_{uds}=20.21\pm 0.10(stat.)\pm 0.22(syst.)$, ${\bar{n}}_c=21.28\pm 0.46(stat.{)}_{-0.36}^{+0.41}(syst.)$ ${\bar{n}}_b=23.14\pm 0.10(stat.{)}_{-0.37}^{+0.38}(syst.)$, from which we derived the differences between the total average charged multiplicities of $c$ or $b$ quark events and light quark events: $\Delta {\bar{n}}_c=1.07\pm 0.47(stat.{)}_{-0.30}^{+0.36}(syst.)$ and $\Delta {\bar{n}}_b=2.93\pm 0.14(stat.{)}_{-0.29}^{+0.30}(syst.)$. 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.

Comments: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters B