Evidence for CP Violation in B0→J/ψπ0 Decays

Abstract

We present measurements of the branching fraction and time-dependent C P asymmetries in B 0 → J / ψ π 0 decays based on 466 × 10 6 Υ ( 4 S ) → B ¯¯¯ B events collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We measure the C P asymmetry parameters S = − 1.23 ± 0.21 ( stat ) ± 0.04 ( syst ) and C = − 0.20 ± 0.19 ( stat ) ± 0.03 ( syst ) , where the measured value of ( S , C ) is 4.0 standard deviations from (0, 0) including systematic uncertainties. The branching fraction is determined to be B ( B 0 → J / ψ π 0 ) = [ 1.69 ± 0.14 ( stat ) ± 0.07 ( syst ) ] × 10 − 5 .