We present the perturbative QCD results for heavy quark event multiplicities in ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ annihilation, which provide that the difference ${\mathrm{\delta }}_{\mathit{Q}\mathit{l}}$ between heavy and light quark event multiplicities at the same c.m.-systems (c.m.s.) energy should be a calculable constant, independent of c.m.s. energy. Published data on heavy quark event multiplicities are presented in this light, and are consistent with the energy independence of the multiplicity difference. Averaging over c.m.s. energy, we find that ${\mathrm{\delta }}_{\mathit{b}\mathit{l}}$=4.3±0.9 and ${\mathrm{\delta }}_{\mathit{c}\mathit{l}}$=2.3±1.0 tracks, while the perturbative QCD expectations are 5.5±0.8 and 1.7±0.5 tracks, respectively.

• Received 24 August 1992

DOI:https://doi.org/10.1103/PhysRevLett.69.3025