Coherent particle production and multiplicities in three-jet-events of Z0 annihilations

Abstract The particle production in hadronic three-jet eventsfrom Z -decays is studied with data from the DELPHI-experiment. The topology dependence of the multiplicityproduced with large angles to the event plane is compared with a LO prediction revealing a 1/ N c -suppressed destructive gluoninterference. The topology dependence of the total charged event multiplicityis compared with a MLLA prediction. A parameter fit to the data results in a precise measurement of the colour factor ratio C A / C F = 2.261 ± 0.014(stat.) ± 0.036(syst.) ± 0.052(theor.) ± 0.041(clus.). The multiplicityof two- gluonsystems is extracted from the measured multiplicitiesover a wide range of energy scale, allowing for studies of the ratio of the multiplicitiesof q - and gg -systems and the ratio of the derivatives of the multiplicitiesw.r.t. energy.