Measurement of the Decays $\mathbf{B}\to \hat{\mathbf{I}}\cdot \mathbf{\ell }\hat{\mathbf{I}}{½}_{\mathbf{\ell }}$ and $\mathbf{B}\to \hat{\mathbf{I}}{\cdot }^{\prime }\mathbf{\ell }\hat{\mathbf{I}}{½}_{\mathbf{\ell }}$ in Fully Reconstructed Events at Belle

Abstract

We report branching fraction measurements of the decays $B^{+}\to \hat{I}\cdot {\ell }^{+}\hat{I}{½}_{\ell }$ and $B^{+}\to \hat{I}{\cdot }^{\prime }{\ell }^{+}\hat{I}{½}_{\ell }$ based on 711~fb${}^{-1}$ of data collected near the $\hat{I}\yen (4S)$ resonance with the Belle experiment at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. This data sample contains 772 million $B\bar{B}$~events. One of the two $B$~mesons is fully reconstructed in a hadronic decay mode. Among the remaining ("signal-$B$") daughters, we search for the $\hat{I}\cdot$~meson in two decay channels, $\hat{I}\cdot \to {\hat{I}}^3{\hat{I}}^3$ and $\hat{I}\cdot \to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$, and reconstruct the $\hat{I}{\cdot }^{\prime }$~meson in $\hat{I}{\cdot }^{\prime }\to \hat{I}\cdot \ddot{I}{€}^{+}\ddot{I}{€}^{-}$ with subsequent decay of the $\hat{I}\cdot$ into ${\hat{I}}^3{\hat{I}}^3$. Combining the two $\hat{I}\cdot$ modes and using an extended maximum likelihood, the $B^{+}\to \hat{I}\cdot {\ell }^{+}\hat{I}{½}_{\ell }$ branching fraction is measured to be $(4.2\pm 1.1(stat.)\pm 0.3(syst.))\times 10^{-5}$. For $B^{+}\to \hat{I}{\cdot }^{\prime }{\ell }^{+}\hat{I}{½}_{\ell }$, we observe no significant signal and set an upper limit of $0.72\times 10^{-4}$ at 90\% confidence level.

8 pages, 4 figures