Skip to main content

Measurement of \(A_{\rm FB}^b\) using inclusive \(b\)-hadron decays


Based on a sample of four million events collected by ALEPH from 1991 to 1995, a measurement of the forward-backward asymmetry in \(Z \rightarrow b\bar{b}\) decays using inclusive final states is presented. High-performance tagging of \(b\bar{b}\) events in a wide angular range is achieved using neural network techniques. An optimal hemisphere charge estimator is built by merging primary and secondary vertex information, leading kaon identification and jet charge in a neural network. The average charge asymmetry, the flavour tagging efficiencies and mean b-hemisphere charges are measured from data and used to extract the pole b asymmetry in the Standard Model

\begin{eqnarray*} \nonumber A^{0,b}_{\rm FB} & = & 0.1011 \, \pm \,0.0027\,(stat) \,\pm \,0.0012\,(syst)\,, \end{eqnarray*}

corresponding to a value of the effective weak mixing angle of

\[ {\rm sin^2} \theta_{\rm W}^{\rm eff} = 0.23189 \pm 0.00056\,. \]

This is a preview of subscription content, access via your institution.

Author information

Authors and Affiliations



Additional information

Received: 4 July 2001 / Published online: 12 November 2001

Rights and permissions

Reprints and Permissions

About this article

Cite this article

The ALEPH Collaboration., Heister et al., A. Measurement of \(A_{\rm FB}^b\) using inclusive \(b\)-hadron decays. Eur. Phys. J. C 22, 201–215 (2001).

Download citation

  • Issue Date:

  • DOI:


  • Neural Network
  • Angular Range
  • Charge Asymmetry
  • Average Charge
  • Secondary Vertex