From the Z decays recorded in 1994 and 1995 by the DELPHI detector at LEP, the charged particle multiplicity of weakly decaying B hadrons was measured to be:4.97±0.03±0.06 excluding the K0 and Λ decay products.
Abreu, P., Cortina Gil, E., DELPHI Collaboration, & et al. (1999). Measurement of the charged particle multiplicity of weakly decaying B hadrons. Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics, 425(3-4), 399-412. https://doi.org/10.1016/S0370-2693(98)00296-2 (Original work published 1998)