Observation of the decay $B^0\to J/\psi \eta$

Abstract

We report the first observation of $B^0\to J/\psi \eta$ decay. These results are obtained from a data sample that contains 449 million $B\bar{B}$ pairs accumulated at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We observe a signal with a significance of 8.1$\sigma$ and obtain a branching fraction of (9.5 $\pm$ 1.7 (stat) $\pm$ 0.8 (syst))$\times 10^{-6}$.

5 pages, 2 figures, submit to PRL (8 pages, 2 figures, ICHEP'06 Conference Paper)