Charged particle multiplicity in e(+)e(-)-> q(q)over-bar events at 161 and 172 GeV and from the decay of the W boson

The data collected by DELPHI in 1996 have been used to measure the average charged particle multiplicities and dispersions in q (q) over bar events at centre-of-mass energies of root s = 161 GeV and root s = 172 GeV, and the average charge multiplicity in WW events at root s = 172 GeV. The multiplicities in q (q) over bar events are consistent with the evolution predicted by QCD. The dispersions in the multiplicity distributions are consistent with Koba-Nielsen-Olesen (KNO) scaling. The average multiplicity of charged particles in hadronic W decays has been measured for the first time; its value, 19.23 +/- 0.74(stat + syst), is consistent with that expected for an e(+)e(-) interaction at a centre-of-mass energy equal to the W mass. The charged particle multiplicity in W decays shows no evidence of effects of colour reconnection between partons from different W's at the present level of statistics. (C) 1998 Elsevier Science B.V.