Measurement of the probability for gluon splitting into $b\overline{b}$ in $Z^{0}$ decays

We present a preliminary measurement of the rate of gluon splitting into bottom quarks, g -> b bbar, in hadronic Z0 decays collected by SLD between 1996 and 1998. The analysis was performed by looking for secondary bottom production in 4-jet events of any primary flavour. 4-jet events were identified, and a topological vertex-mass technique was applied to each jet in order to identify b or bbar jets. The upgraded CCD based vertex detector gives very high B-tagging efficiency, especially for B hadrons of the low energies typical of this process. The two most nearly collinear b/bbar jets were tagged as originating from g -> b bbar. We measured the rate of secondary b/bbar production per hadronic event, g_bb, to be (3.07+-0.71(stat.)+-0.66(syst.)) * 10**-3