Measurement of the branching fraction of $B\to D^{(\ast )}\ddot{I}€\ell \hat{I}½$ at Belle using hadronic tagging in fully reconstructed events

Abstract

We report a measurement of the branching fraction of the decay $B\to D^{(\ast )}\ddot{I}€\ell \hat{I}½$. The analysis uses 772$\times 10^6$ $B\bar{B}$ pairs produced in $e^{+}{e}^{-}\to \hat{I}\yen (4S)$ data recorded by the Belle experiment at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The tagging $B$ meson in the decay is fully reconstructed in a hadronic decay mode. On the signal side, we reconstruct the decay $B\to D^{(\ast )}\ddot{I}€\ell \hat{I}½$ $(\ell =e,\hat{I}¼)$. The measured branching fractions are $\mathcal{B}(B^{+}\to D^{-}\ddot{I}{€}^{+}{\ell }^{+}\hat{I}½)$ = [4.55 $\pm$ 0.27 (stat.) $\pm$ 0.39 (syst.)]$\times 10^{-3}$, $\mathcal{B}(B^0\to {\bar{D}}^0\ddot{I}{€}^{-}{\ell }^{+}\hat{I}½)$ = [4.05 $\pm$ 0.36 (stat.) $\pm$ 0.41 (syst.)]$\times 10^{-3}$, $\mathcal{B}(B^{+}\to D^{\ast -}\ddot{I}{€}^{+}{\ell }^{+}\hat{I}½)$ = [6.03 $\pm$ 0.43 (stat.) $\pm$ 0.38 (syst.)]$\times 10^{-3}$, and $\mathcal{B}(B^0\to {\bar{D}}^{\ast 0}\ddot{I}{€}^{-}{\ell }^{+}\hat{I}½)$ = [6.46 $\pm$ 0.53 (stat.) $\pm$ 0.52 (syst.)]$\times 10^{-3}$. These are in good agreement with the current world average values.

8 pages, 2 figures, submitted to PRD