Measurement of Rb using a vertex mass tag

Abstract

We report a new measurement of Rb = ГZ0→bbГZ0→hadrons using a double tag technique, where the b hemisphere selection is based on the reconstructed mass of the B hadron decay vertex. The measurement was performed using a sample of 130 × 103 hadronic Z0 events, collected with the SLD detector at SLC. The method utilizes the 3D vertexing abilities of the CCD pixel vertex detector and the small stable SLC beams to obtain a high b-tagging efficiency and purity. We obtain Rb = 0.2142 ° 0.0034(stat) ° 0.0015(syst) ± 0.0002(Rc). © 1998 The American Physical Society.