Measurements of $Z^0$ to Heavy-quark couplings at SLD

Abstract

We present measurements of $Z^0$ to heavy-quark coupling electroweak parameters, $R_b$, $R_c$, and parity-violation parameter $A_c$, from SLD. The measurements are based on approximately 550k hadronic $Z^0$ events collected in 1993-98. Obtained preliminary results of $R_b$ and $R_c$ measurements are $R_b=0.2159\pm 0.0014\pm 0.0014$ and $R_c=0.1685\pm 0.0047\pm 0.0043$. In the $A_c$ measurement, we use four methods to determine the initial-quark charge: combined Kaon charge and Vertex charge, lepton, exclusively reconstructed D*, D-mesons, and a new method using inclusive soft-pion from D*. The preliminary results of these four methods were combined to give $A_c=0.634\pm 0.027$.

10 pages 5 figures Latex, Contribution to DPF '99