Session J10 - Electro Weak Interactions.
CONTRIBUTED session, Sunday morning, April 20
Room 5, Renaissance
We report a measurement of R_b=\Gamma_Z^o\rightarrow bøverlineb/ \Gamma_Z^0\rightarrow hadrons using a double tag technique where the b selection is based on topological reconstruction of the mass of the B-decay vertex. The measurement was performed using a sample of 150k hadronic Z^0 events collected with the SLD at the SLAC Linear Collider during 1993-1995. The method utilizes the 3-D vertexing abilities of the SLD CCD pixel vertex detector and the small stable SLC beams to obtain a high b tagging efficiency of 37 for a purity of 97. The high purity reduces the systematics introduced by charm contamination and correlations with R_c. We obtain errors of \delta R_b=\pm0.0032_stat.\pm0.0021_syst.\pm0.0007_R_c.