Measurement of the branching fractions of the $B^{+}\to \hat{I}\cdot {\ell }^{+}\hat{I}{½}_{\ell }$ and $B^{+}\to \hat{I}{\cdot }^{\prime }{\ell }^{+}\hat{I}{½}_{\ell }$ decays with signal-side only reconstruction in the full $q^2$ range

Abstract

The branching fractions of the decays $B^{+}\to \hat{I}\cdot {\ell }^{+}\hat{I}{½}_{\ell }$ and $B^{+}\to \hat{I}{\cdot }^{\prime }{\ell }^{+}\hat{I}{½}_{\ell }$ are measured, where $\ell$ is either an electron or a muon, using a data sample of $711{\mathrm{fb}}^{-1}$ containing $772\times 10^{6}B\bar{B}$ pairs collected at the $\hat{I}\yen (4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. To reduce the dependence of the result on the form factor model, the measurement is performed over the entire $q^2$ range. The resulting branching fractions are $\mathcal{B}(B^{+}\to \hat{I}\cdot {\ell }^{+}\hat{I}{½}_{\ell })=(2.83\pm 0.55_{(stat.)}\pm 0.34_{(syst.)})\times 10^{-5}$ and $\mathcal{B}(B^{+}\to \hat{I}{\cdot }^{\prime }{\ell }^{+}\hat{I}{½}_{\ell })=(2.79\pm 1.29_{(stat.)}\pm 0.30_{(syst.)})\times 10^{-5}$.

9 pages, 3 figures