Search for $B^{+}\to e^{+}\hat{I}½$ and $B^{+}\to \hat{I}{¼}^{+}\hat{I}½$ decays using hadronic tagging

Abstract

We present a search for the rare leptonic decays $B^{+}\to e^{+}\hat{I}{½}_e$ and $B^{+}\to \hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$, using the full $\hat{I}\yen (4S)$ data sample of $772\times 10^6$ $B\bar{B}$ pairs collected with the Belle detector at the $\text{KEKB}$ asymmetric-energy $e^{+}{e}^{-}$ collider. One of the $B$ mesons from the $\hat{I}\yen (4S)\to B\bar{B}$ decay is fully reconstructed in a hadronic mode, while the recoiling side is analyzed for the signal decay. We find no evidence of a signal in any of the decay modes. Upper limits of the corresponding branching fractions are determined as $\mathcal{B}(B^{+}\to e^{+}\hat{I}{½}_e)<3.5\times 10^{-6}$ and $\mathcal{B}(B^{+}\to \hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼)<2.7\times 10^{-6}$ at 90$\%$ confidence level.

13 pages, 7 figures, Submitted to PRD