Hadronization properties of b quarks compared to light quarks in $e^{+}e^{-} \to q\overline{q}$ from 183 to 200 GeV

The DELPHI detector at LEP has collected 54 pb$^{-1}$ of dataat a centre-of-mass energy around 183 GeV during 1997,158 pb$^{-1}$ around 189 GeV during 1998,and 187 pb$^{-1}$ between 192 and 200 GeV during 1999.These data were used tomeasure the average charged particle multiplicity in $e^+e^-ightarrow bar{b}$ events, $langle nangle_b$, and the difference $delta_{bl}$between $langle nangle_b$ and themultiplicity, $langle nangle_ll$, in generic light quark (u,d,s) events:egin{eqnarray*}delta_{bl}m{(183 , GeV)} &=& 4.55 pm 1.31 (stat) pm 0.73 (syst) \delta_{bl}m{(189 , GeV)} &=& 4.43 pm 0.85 (stat) pm 0.61 (syst) \delta_{bl}m{(200 , GeV)} &=& 3.42 pm 0.89 (stat) pm 1.01 (syst) , .end{eqnarray*}This result is consistent with QCD predictions, while it isinconsistent with calculations assuming that themultiplicity accompanying the decay of a heavy quark is independent of the mass ofthe quark itself.