Measurements of BR(b \(\to \tau^- \bar{\nu}_{\tau}\)X) and BR(b\(\to \tau^- \bar{\nu}_{\tau}{\mathrm D}^{\ast\pm}\) X) and upper limits on BR(B\(^- \to \tau^- \bar{\nu}_{\tau})\) and BR(b \(\to{\mathrm s} \nu \bar{\nu})\)

  • The ALEPH Collaboration
  • R. Barate et al.
Experimental physics


Inclusive branching ratios involving b \(\to \tau\) transitions are measured in approximately four million hadronic Z decays collected by the ALEPH detector at LEP. The fully-inclusive branching ratio BR(b \(\to \tau^- \bar{\nu}_{\tau}\) X) and the semi-inclusive branching ratio BR(b \(\to \tau^- \bar{\nu}_{\tau} {\rm D}^{\ast\pm}\)X) are measured to be \((2.43 \pm 0.20 \pm 0.25)%\) and \((0.88\pm 0.31\pm 0.28)%\), in agreement with the standard model predictions. Upper limits on the branching fractions BR(B\(^- \to \tau^- \bar{\nu}_{\tau})\) and BR(b \(\to{\mathrm s} \nu \bar{\nu})\) are set to \(8.3 \times 10^{-4}\) and \(6.4 \times 10^{-4}\) at the 90% C.L. These results allow a 90% C.L. lower limit of 0.40 GeV/\(c^2)^{-1}\) to be set on the \(\tan\beta/m_{{\mathrm H}^\pm}\) ratio, in the framework of type-II two-Higgs-doublet models.


Model Prediction Lower Limit Standard Model Prediction Aleph Detector 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2001

Authors and Affiliations

  • The ALEPH Collaboration
  • R. Barate et al.
    • 1
  1. 1.Laboratoire de Physique des Particules (LAPP), IN2P3-CNRS, 74019 Annecy-le-Vieux Cedex, France FR

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