The charged multiplicity has been measured at the $\Upsilon \mathrm{}\left(4S\right)\mathrm{}$ and a value of 5.75±0.1±0.2 has been obtained for the mean charged multiplicity in $B$-meson decay. Combining this result with the measurement of prompt leptons from $B$ decay, the values 4.1±0.35±0.2 and 6.3±0.2±0.2 are found for the semileptonic and nonleptonic charged multiplicities, respectively. If $b\to c$ dominance is assumed for the weak decay of the $B$ meson, then the semileptonic multiplicity is consistent with the recoil mass determined from the lepton momentum spectrum.

• Received 26 May 1982

DOI:https://doi.org/10.1103/PhysRevLett.49.357