Charged-particle multiplicities of quark and gluon jets in e+ e− annihilation at TRISTAN

Charged-particle multiplicity was studied in e+e− annihilation at s = 57.8 GeV using the TOPAZ detector at TRISTAN. The average multiplicity was 〈nch〉 = 17.64± 0.05(stat.) ± 0.41(syst.). It was found that the multiplicity depends on the thrust (T) of an event. From extrapolating this relation to T = 23, the multiplicity for three-fold symmetric events was estimated to be 〈nch〉T = 23 = 23.50−1.45+1.25. From this, the multiplicity ratio between gluon- and quark-jet was estimated to be rgq = 1.46−0.13+0.09 without any possible bias from jet clustering.