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

The ALEPH Collaboration R. Barate; et al.

doi:doi:10.1007/s100520100612

EPJ

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

The ALEPH Collaboration R. Barate and et al.

(Received: 2 October 2000 / Published online: 15 March 2001 -© Springer-Verlag 2001)

Abstract
Inclusive branching ratios involving ${\mathrm b} \to \tau$ transitions are measured in approximately four million hadronic Z decays collected by the ALEPH detector at LEP. The fully-inclusive branching ratio $\mathrm{BR}(\mathrm{b}\to \tau^- \bar{\nu}_{\tau} \mathrm{X})$ and the semi-inclusive branching ratio $\mathrm{BR}({\mathrm{b}} \to \tau^- \bar{\nu}_{\tau} \mathrm{D}^{\ast\pm}\mathrm{X})$ 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 $\mathrm{BR}(\mathrm{B}^- \to \tau^- \bar{\nu}_{\tau})$ and $\mathrm{BR}(\mathrm{b} \to \mathrm{s} \nu \bar{\nu})$ 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/c²)^-1 to be set on the $\tan\beta/m_{\mathrm{H}^\pm}$ ratio, in the framework of type-II two-Higgs-doublet models.

Società Italiana di Fisica, Springer-Verlag 2001