UNIFIED QCD DESCRIPTION OF HADRON AND JET MULTIPLICITIES

The evolution equation for parton multiplicities in quark and gluon je ts which takes into account the soft gluon interference and energy con servation is solved numerically using the initial conditions at thresh old. If the k perpendicular to-cutoff Q(c) is lowered towards the hadr onic scale eo of a few hundred MeV, the jets are fully resolved into h adrons. Both hadron and jet multiplicities in e(+)e(-) annihilation ar e well described with a common normalization. Evidence is presented wi thin this perturbative approach that the coupling alpha(s)(k perpendic ular to) rises by an order of magnitude when approaching the low energ y region. The ratio of hadron multiplicities in gluon and quark jets i s found smaller than in previous approximate solutions of the evolutio n equation. (C) 1998 Elsevier Science B.V.