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Measurement of the forward-backward asymmetries of \(e^ + e^- \rightarrow Z \rightarrow b \overline{b}\) and \(e^ + e^- \rightarrow Z \rightarrow c \overline{c}\) using prompt leptons

  • experimental physics
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Abstract.

The forward-backward asymmetries of the processes \({e^ + e^-\ \rightarrow Z\ \rightarrow b \overline{b}}\) and \(e^ + e^- \rightarrow Z\;\; \rightarrow c \overline{c}\) were measured from a sample of hadronic \(Z\;\;\) decays collected by the DELPHI experiment between 1993 and 1995. Enriched samples of \(b\bar{b}\) and \(c\bar{c}\) events were obtained using lifetime information. The tagging of b and c quarks in these samples was based on the semileptonic decay channels \(b/c \rightarrow X + \mu \) and \( b/c \rightarrow X + e \) combined with charge flow information from the hemisphere opposite to the lepton.

Combining the \(A_{\mathrm{FB}}^{\mathrm{b\overline{\mathrm{b}}}}\) and \(A_{\mathrm{FB}}^{\mathrm{c\overline{\mathrm{c}}}}\) measurements presented in this paper with published results based on 1991 and 1992 DELPHI data samples, the following pole asymmetries were obtained: \( \begin{array}{l} A_{\mathrm{FB}}^{\mathrm{0,b}} = 0.1021 \pm 0.0052 \mathrm{~(stat)} \pm 0.0024 \mathrm{~(syst)} \\ A_{\mathrm{FB}}^{\mathrm{0,c}} = 0.0728 \pm 0.0086 \mathrm{~(stat)} \pm 0.0063 \mathrm{~(syst)} \end{array} \) The effective value of the weak mixing angle derived from these measurements is \( \sin ^2 \theta_{\mathrm{W,eff}}^{\mathrm{lept}} = 0.23170 \pm 0.00097 . \)

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Received: 10 December 2003, Revised: 3 February 2004, Published online: 9 March 2004

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The DELPHI Collaboration. Measurement of the forward-backward asymmetries of \(e^ + e^- \rightarrow Z \rightarrow b \overline{b}\) and \(e^ + e^- \rightarrow Z \rightarrow c \overline{c}\) using prompt leptons. Eur. Phys. J. C 34, 109–125 (2004). https://doi.org/10.1140/epjc/s2004-01708-6

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