Measurement oft he Polarized Forward - Backward

We present a direct measurement of the parity-violating parameter Ab by analyzing the left-right forward-backward asymmetry of b quarks in e+ e– + 2° + b;. The SLD experiment observes hadronic decays of 2° bosons produced at resonance in collisions of longitudinally polarized. . elect rons and unpolarized positrons at the SLC. Heavy flavor decays of the 2° are identified by taking advantage of the long lifetime of B hadrons, the small, stable SLC beam spot, and precise tracking from: SLD. The asymmetry Ab is measured with a self-calibrating technique employing momentum-weighted track charge from both hemispheres in the tagged events. From our 1994–1995 sample of 3.6 pb-l of e+e-annihilation data with a luminosity-wei hted average e– polarization of 5 77.3%, and our 1993 sample of 1.8 pb-with a luminosity-weighted polarization of 63.1%, we obtain Ab(pre]iminary) = 0.843 t 0.046 (stat.) ~ o.051(syst.).