Measurement of the Parity-Violation ParametersAbandAcfrom the Left-Right Forward-Backward Asymmetry of Leptons in Hadronic Events at theZ0Resonance

The parity-violating parameters ${A}_{b}$ and ${A}_{c}$ are directly measured by the SLD experiment at the SLAC Linear Collider in ${e}^{+}{e}^{\ensuremath{-}}$ collisions with polarized electrons at the ${Z}^{0}$ resonance. Leptons with distinctive total and transverse momenta are used to select and analyze ${Z}^{0}\ensuremath{\rightarrow}b\overline{b}$ and ${Z}^{0}\ensuremath{\rightarrow}c\overline{c}$ events. ${A}_{b}$ and ${A}_{c}$ are extracted by forming the left-right forward-backward asymmetry in electron beam polarization and quark polar angle. From our 1993 sample of 1.8 p${\mathrm{b}}^{--1}$ of ${Z}^{0}$ decay data with an average electron beam polarization of 63% we find ${A}_{b}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.91\ifmmode\pm\else\textpm\fi{}0.14$ (stat) $\ifmmode\pm\else\textpm\fi{}0.07$ (syst) and ${A}_{c}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.37\ifmmode\pm\else\textpm\fi{}0.23$ (stat) $\ifmmode\pm\else\textpm\fi{}0.21$ (syst).