Author(s): The SLD Collaboration Presenting author: Tracy Usher Corresponding author's e-mail: usher@slac.stanford.edu Title of the presentation: Direct Measurements of Ab and Ac using Vertex/Kaon Charge Tags at SLD Link to the full paper: Session of 1st preference: 5-Test of the Standard Model Session of 2nd preference:   Abstract   We present measurements of the parity-violation parameters A_b and A_c at the Z pole. These measurements include the data taken with the SLD detector at the SLAC Linear Collider (SLC) during the period 1996-98. Heavy flavor events are selected with high efficiency and purity using the invariant mass of displaced vertices, identified with the SLD precision CCD vertex detector. Two methods are used for quark/antiquark discrimination: one uses the net charge of the displaced vertex, the second uses the charge of tracks in the displaced vertex that are identified as kaons by the SLD Cherenkov Ring Imaging Detector (CRID). The signal purities and analyzing powers are calibrated from the data to reduce the systematic errors and avoid experimental bias.