Abstract
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.
Highlights
The study of heavy quark pair production in e+e−collisions with centre-of-mass energies greatly exceeding the heavy quark masses provides important tests of perturbative QCD
For a recent review see for example [4]. This prediction is in striking contrast with that from a more phenomenological approach, the so-called naıve model [5, 6], which assumes that the hadron multiplicity accompanying the heavy hadrons in bbevents is the same as the multiplicity in light quark events at the energy left to the system once the heavy quarks have fragmented
The numbers of events collected at these higher energies are much smaller than at LEP1, and the results will be much less precise. In this analysis we have measured the mean charged particle multiplicity separately for b, c and uds initiated event√s observed with th√e OPAL detector at all eleven LEP energies above the Z0 resonance, ranging from s = 130 GeV to s = 206 GeV, and derived at each energy the difference δbl
Summary
The study of heavy quark pair production in e+e−collisions with centre-of-mass energies greatly exceeding the heavy quark masses provides important tests of perturbative QCD. For a recent review see for example [4] This prediction is in striking contrast with that from a more phenomenological approach, the so-called naıve model [5, 6], which assumes that the hadron multiplicity accompanying the heavy hadrons in bbevents is the same as the multiplicity in light quark events at the energy left to the system once the heavy quarks have fragmented. The numbers of events collected at these higher energies are much smaller than at LEP1, and the results will be much less precise In this analysis we have measured the mean charged particle multiplicity separately for b, c and uds initiated event√s observed with th√e OPAL detector at all eleven LEP energies above the Z0 resonance, ranging from s = 130 GeV to s = 206 GeV, and derived at each energy the difference δbl. Their measured values of δbl were found to be consistent with an energy independent extrapolation from lower energy data, and inconsistent with the prediction of the naıve model by more than three standard deviations
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