Observation of the Decay B=> J/psi eta K and Search for X(3872)=> J/psi eta

B. Aubert

We report the observation of the $B$ meson decay $B^{\pm }\to J/\psi \eta K^{\pm }$ and evidence for the decay $B^0\to J/\psi \eta K_S^0$, using {90} million $BBbar$ events collected at the $\ensuremath…