Charged particle multiplicities in e+e- annihilation at 29 GeV: measurements in the central rapidity regions and in the gluon jet

The charged particle multiplicity distribution for e+e- annihilations at √s = 29 GeV has been measured using the High Resolution Spectrometer at PEP. Firstly, the multiplicity distributions for particles selected in different central rapidity spans are presented. All of these are well represented by the negative binomial distribution. As the rapidity span is narrowed, the distributions become broader and approach a constant value of the parameter K. Secondly, the charged particle multiplicities of the quark and gluon jets in the three-fold symmetric e+e- → qantiqg events have been studied. A value of < n >g = 6.7 +1.1-2.1 ± 1.0 for gluon jets with an energy of 9.7 +1.5-2.0 GeV is measured. The ratio, < n >g/ < g >q, is 1.29 +0.21-0.41 ± 0.20, which is significantly lower than the value of 9/4 naively expected from the ratio of the quark-to-quark color charges. 5 figs.; 13 refs