A Measurement of the Forward-BackwardAsymmetry of e + e � ! bbby Applying a Jet Charge Algorithmto Lifetime Tagged EventsThe

The forward-backward asymmetry of e + e ? ! Z 0 ! bb has been measured using approximately 2.15 million hadronic Z 0 decays collected at the LEP e + e ? collider with the OPAL detector. A lifetime tag technique was used to select an enriched bb event sample. The measurement of the bb asymmetry was then performed using a jet charge algorithm to determine the direction of the primary quark. were measured where, in each case, the rst error is statistical, the second is systematic and the third term gives the variation due to a change (? bb =? had) in the value of ? bb =? had = 0:216 assumed. The dependence on the assumed charm asymmetry at the same energy is (A b FB) +0:077(A c FB). Assuming the Standard Model form for the couplings, these measurements correspond to an eeective weak mixing angle of: sin 2 ee;e +16 ?19 GeV/c 2 , where the rst error is statistical and the second is systematic. The Higgs mass assumed is 300 GeV/c 2. A variation in the assumed mass of the Higgs boson between 60 and 1000 GeV/c 2 corresponds to an uncertainty in sin 2 ee;e W of 0:00006 and on M top of +20 ?26 GeV/c 2 .