Study of time-dependent CP-violation in B⁰ → J/ψ π⁰ decay

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We report a measurement of CP asymmetry parameters in the b → ccd-transition-induced decays B⁰(B⁰) → J/ψpi⁰. The analysis is based on a 140 fb⁻¹ data sample accumulated at the Υ(4S) resonance by the Belle detector at the KEKB asymmetric-energy e+ e- collider. We fully reconstruct one neutral B meson in the J/ψ π⁰ 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 violation parameters: S(J/ψπ⁰)= -0.72 ±0.42 (stat) ± 0.08(syst) A(J/ψπ⁰)= -0.01 ±0.29 (stat) ± 0.07(syst).