A Preliminary Improved Measurement of the B Hadron Energy Distribution in Z 0 Decays

We h a v e measured the B hadron energy distribution in Z 0 decays using a new technique applied to a sample of inclusive B decays recorded in the SLD experiment at SLAC b e t w een 1996 and 1997. The upgraded CCD vertex detector is used to reconstruct B-decay v ertices with high eeciency and purity, and to provide precise measurements of the kinematic quantities used in this technique. For each reconstructed B-decay v ertex, the part of the B energy missing from the vertex is derived from the kinematic quantities. B vertices with low missing mass are selected to provide a very high purity sample and to obtain good energy resolution. We compare the scaled B hadron energy distribution with the predictions of several QCD and phenomenological models of heavy quark fragmention. The average scaled energy x B is measured to be 0.7190.005 stat.0.001 unfolding preliminary.