Measurement of the forward-backward asymmetry of charm and bottom quarks at theZ pole usingD ^*± mesons

Abstract

The forward-backward asymmetries for the processes$e^ + e^ - \to c\bar c$ and$e^ + e^ - \to b\bar b$ at theZ resonance are measured using identifiedD ^*± mesons. In 905,000 selected hadronic events, taken in 1991 and 1992 with the DEL-PHI detector at LEP, 4757D ^*+→D ⁰π⁺ decays are reconstructed. Thec andb quark forward-backward asymmetries are determined to be:

$$\begin{gathered} A_{FB}^{c\bar c} = 0.077 \pm 0.029(stat) \pm 0.012(sys), \hfill \\ A_{FB}^{b\bar b} = 0.059 \pm 0.062(stat) \pm 0.024(sys). \hfill \\ \end{gathered} $$

Constraining theb asymmetry to the value measured by DELPHI using independent analyses, the charm asymmetry is determined to be:

$$A_{FB}^{c,const} = 0.068 \pm 0.027(stat) \pm 0.011(sys).$$

. This result corresponds to an effective electroweak mixing angle measured using charm quark events of:

$$\sin ^2 \theta _{eff}^{lept} = 0.2307 \pm 0.0062(stat) \pm 0.0026(sys).$$