Search for Rare $b\to d{\ell }^{+}{\ell }^{-}$ Transitions at Belle

Abstract

We present the results of a search for the $b\to d{\ell }^{+}{\ell }^{-}$ flavor-changing neutral-current rare decays $B^{+,0}\to (\hat{I}\cdot ,\ddot{I}‰,\ddot{I}{€}^{+,0},\ddot{I}{}^{+,0})e^{+}{e}^{-}$ and $B^{+,0}\to (\hat{I}\cdot ,\ddot{I}‰,\ddot{I}{€}^0,\ddot{I}{}^{+})\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ using a $711$ fb${}^{-1}$ data sample that contains $772\times 10^6$ $B\overline{B}$ events. The data were collected at the $\hat{I}\yen (4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We find no evidence for signal and set upper limits on branching fractions at the $90\%$ confidence level in the range $(3.8-47)\times 10^{-8}$ depending on the decay channel. The obtained limits are the world's best results. This is the first search for the channels $B^{+,0}\to (\ddot{I}‰,\ddot{I}{}^{+,0})e^{+}{e}^{-}$ and $B^{+,0}\to (\ddot{I}‰,\ddot{I}{}^{+})\hat{I}{¼}^{+}\hat{I}{¼}^{-}$.

7 pages, 12 figures