Measurement of the parity-violation parameter Ab from the left-right forward-backward asymmetry of b quark production in Z0 decays using a momentum-weighted track-charge technique

Using an impact parameter tag to select an enriched sample of Z0→bb̄ events, and the net momentum-weighted track charge to identify the sign of the charge of the underlying b quark, we have measured the left-right forward-backward asymmetry for b quark production as a function of polar angle. Based on 1.8 pb-1 of Z0 decay data produced with a mean electron beam polarization of Pe=63%, this yields a direct measurement of the extent of parity violation in the Zbb coupling of Ab=0.87±0.11(stat)±0. 09(syst).