Direct Measurement of Ab and Ac at the Z0 Pole Using a Lepton Tag

The parity violation parameters Ab and Ac of the Zbb¯ and Zcc¯ couplings have been measured directly, using the polar angle dependence of the Z0-pole polarized cross sections. Bottom and charmed hadrons were tagged via semileptonic decays. Both the muon and electron identification algorithms take advantage of new multivariate techniques, incorporating for the first time information from the SLD Čerenkov Ring Imaging Detector. Based on the 1993–1995 SLD sample of 150 000 Z0 decays produced with highly polarized electron beams, we measure Ab=0.910±0.068(stat)±0.037(syst), Ac=0.642±0.110(stat)±0.063(syst).