Measurement of the $B$ hadron energy distribution in $Z^0$ decays

We have measured the $B$ hadron energy distribution in $Z^0$ decays using a sample of semileptonic $B$ decays recorded in the SLD experiment at SLAC. The energy of each tagged $B$ hadron was reconstructed using information from the lepton and a partially reconstructed charm-decay vertex. We compared the scaled energy distribution with several models of heavy quark fragmentation. The average scaled energy of primary $B$ hadrons was found to be $〈x_{E_B}〉=0.716\mathrm{}\pm 0.011\left(\mathrm{stat}{)}_{-0.022}^{+0.021\mathrm{}}\right(\mathrm{syst})$.