  We study bottom-quark fragmentation in e+e- annihilation, top and Higgs decay
H -> b bbar, using Monte Carlo event generators, as well as calculations, based
on the formalism of perturbative fragmentation functions, which resum soft- and
collinear-radiation effects in the next-to-leading logarithmic approximation.
We consider the PYTHIA and HERWIG generators, and implement matrix-element
corrections to the parton shower simulation of the H -> b bbar process in
HERWIG. We tune the Kartvelishvili, string and cluster models to B-hadron data
from LEP and SLD, and present results in both x_B and moment spaces. The
B-hadron spectra yielded by HERWIG, PYTHIA and resummed calculations show small
discrepancies, which are due to the different approaches and models employed
and to the quality of the fits to the e+e- data.
