Observation of the Decay B0→J/ψη

We report the first observation of B-0 -> J/psi eta decay. These results are obtained from a data sample that contains 449x10(6) B (B) over bar pairs accumulated at the Upsilon(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 +/- 1.7(stat)+/- 0.8(syst))x10(-6).