Charged particle multiplicities in heavy and light quark initiated events above the Z0 peak

The mean charged particle multiplicity has been measured separately for heavy and light quark initiated events produced in e+e- annihilations at LEP. In particular, the energy dependence of their difference has been determined, for which theoretical predictions exist. Perturbative QCD calculations in the MLL approximation with the assumption of Local Parton Hadron Duality predict this difference to be energy independent, due to the combination of coherence and quark-mass effects. In contrast, a more phenomenological naive model, which assumes that the multiplicity accompanying the decay of a heavy quark is independent of the quark mass itself, predicts a difference which decreases with energy