Study of time-dependent CP violation in B0 -> J/Psi pi0 decays

We report a measurement of CP asymmetry parameters in the decay B0(B0bar) -> J/Psi pi0, which is governed by the b->c cbar d transition. The analysis is based on a 140/fb data sample accumulated at the Upsilon(4S) resonance by the belle detector at the KEKB asymmetric-energy e+e- collider. We fully reconstruct one neutral B meson in the J/Psi pi0 final state. The accompanying B meson flavor is identified by its decay products. From the distribution of proper time intervals between the two B decays, we obtain the following CP-violating parameters: S_{J/Psi pi0}=-0.72+-0.42+-0.09 and A_{J/Psi pi0}=-0.01 +-0.29+-0.03.