Charged particle multiplicity in three-jet events and two-gluon systems
The charged particle multiplicity in hadronic three-jet events from Z decays is investigated. The topology dependence of the event multiplicity is found to be well described by a modified leading logarithmic prediction. A parameter fit of the prediction to the data yields a measurement of the colour factor ratio C A /C F with the result
in agreement with the SU(3) expectation of QCD. The quark-related contribution to the event multiplicity is subtracted from the three-jet event multiplicity resulting in a measurement of the multiplicity of two-gluon colour-singlet states over a wide energy range. The ratios of the gluon and quark multiplicities and of their derivatives are compared with perturbative calculations.
While a good agreement between calculations and data is observed for r (1), larger deviations are found for r indicating that non-perturbative effects are more important for r than for r (1).
© Springer-Verlag, 2005