IMPROVED MEASUREMENT OF THE PROBABILITY FOR GLUON SPLITTING INTO bb̄ IN Z DECAYS

We have measured gluon splitting into bottom quarks, g → bb̄, 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 flavor. 4-jet events were identified, and in each event a topological vertex-mass technique was applied to the two jets closest in angle in order to identify them as b or b jets. The upgraded CCD-based vertex detector gives very high B-tagging efficiency, especially for B hadrons with the low energies typical of this process. We measured the rate of g → bb̄ production per hadronic event, gbb̄, to be (2.44 ± 0.59(stat.) ± 0.34(syst.))× 10−3. (Submitted to Physics Letters B) ∗ Work supported by Department of Energy contract DE-AC03-76SF00515 (SLAC).