Measurement of CP asymmetries in B0→K0π0 decays

We report measurements of CP violation parameters in B0→K0π0 decays based on a data sample of 657×106BB̄ pairs collected with the Belle detector at the KEKB e+e- asymmetric-energy collider. We use B0→KS0π0 decays for both mixing-induced and direct CP violating asymmetry measurements and B0→KL0π0 decays for the direct CP violation measurement. The CP violation parameters obtained are sin 2 1eff=+0.67±0. 31(stat)±0.08(syst) and AK0π0=+0.14±0.13(stat)±0. 06(syst). The branching fraction of B0→K0π0 decay is measured to be B(B0→K0π0)=(8.7±0.5(stat.)±0.6(syst.))×10 -6. The observed AK0π0 value differs by 1.9 standard deviations from the value expected from an isospin sum rule. © 2010 The American Physical Society.