Measurement of $A_{FB}^{\overline{b}b}$ in Hadronic Z Decays using a Jet Charge Technique

The $\BB$ forward-backward asymmetry %, $\AFBbb$, has been determined from the average charge flow %, $\langle Q_{FB}\rangle$, measured in a sample of 3,500,000 hadronic Z decays collected with the DELPHI detector in 1992 - 1995. The measurement is performed in an enriched $\BB$ sample selected using an impact parameter tag and results in the following values for the $\BB$ forward-backward asymmetry: \begin {center} \begin{tabular}{ccl} \AFBbb (89.55 GeV) & = & $0.068\,\ \pm0.018\,\ (\mbox{stat.})\pm0.0013 (\mbox{syst.})$ \\ \AFBbb (91.26 GeV) & = & $0.0982\pm0.0047(\mbox{stat.})\pm0.0016(\mbox{syst.})$ \\ \AFBbb (92.94 GeV) & = & $0.123\,\ \pm0.016\,\ (\mbox{stat.})\pm0.0027(\mbox{ syst.})$ \\ \end{tabular} \end{center} %at an average center of mass energy of 91.251\, GeV . % The $\BB$ charge separation %, $\db$, required for this analysis is directly measured in the b tagged sample, while the other charge separations %, $\ddusc$, are obtained from a fragmentation model precisely calibrated to data. % The effective weak mixing angle %, $\sweff$, is deduced from the measurement to be: \begin {center} \begin{tabular}{ccl} \sweff & =& $ 0.23186\pm0.00083$ \end{tabular} \end{center}