Evidence for CP Violation in B⁺ → K*(892)⁺π⁰ from a Dalitz Plot Analysis of B⁺ → K_s⁰π⁺π⁰ Decays

We report a Dalitz plot analysis of charmless hadronic decays of charged B mesons to the final state K_s⁰ π⁺π⁰ using the full BABAR data set of 470.9 ± 2.8 million BB̅ events collected at the Υ(4S) resonance. We measure the overall branching fraction and CP asymmetry to be Β(B⁺ → K⁰ π⁺π⁰) = (31.8 ± 1.8 ± 2.1_{-0.0}^{+6.0}) x 10⁻⁶ and A_{CP}(B⁺ → K⁰ π⁺π⁰) = 0.07 ± 0.05 ± 0.03_{-0.03}^{+0.02}, where the uncertainties are statistical, systematic, and due to the signal model, respectively. This is the first measurement of the branching fraction for B⁺ → K⁰ π⁺π⁰. We find first evidence of a CP asymmetry in B⁺ → K*(892)⁺π⁰ decays: A_{CP}(B⁺ → K*(892)⁺π⁰) = -0.52 ± 0.14 ± 0.04_{-0.02}^{+0.04}. The significance of this asymmetry, including systematic and model uncertainties, is 3.4 standard deviations. We also measure the branching fractions and CP asymmetries for three other intermediate decay modes.