Speaker
Jan Hasenbusch
(Univ. of Bonn)
Description
We report the first branching fraction measurement of the inclusive Cabibbo favoured semileptonic decay $B\to X_c \tau\nu$ by the Belle experiment. The branching fraction of this kinematically suppressed mode is highly sensitive to new physics beyond the Standard Model, such as a charged Higgs, which couples strongly to the massive $\tau$ lepton and interfere with the Standard Model process. This measurement will shed light on the contributions from all tauonic $B$ decay modes, including high mass and non-resonant contributions, $B \to D^{**}/D^{(*)}n\pi \tau \nu$ which may be the cause for observed excesses above the SM in the exclusive channels. The full Belle dataset is used, containing 772 million $B\bar{B}$ meson pairs recorded near the $\Upsilon(4S)$ resonance at the KEKB asymmetric-energy $e^+e^-$ collider. The $B$ meson events are tagged by fully reconstructing one $B$ in a hadronic mode. The charm meson on the signal side is identified by the presence of a wrong-sign lepton, and the $\tau$ is reconstructed in several leptonic and hadronic modes. Multivariate selection techniques are used to optimise the signal selection.
Author
Prof.
Youngjoon Kwon
(Yonsei University)
