Evidence for CP violation in B+→K*(892)+π0 from a Dalitz plot analysis of B+→KS0π+π0 decays

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Abstract

We report a Dalitz plot analysis of charmless hadronic decays of charged $B$ mesons to the final state ${K}_{S}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}$ using the full BABAR data set of $470.9\ifmmode\pm\else\textpm\fi{}2.8\text{ }\text{ }\mathrm{million}$ $B\overline{B}$ events collected at the $\mathrm{\ensuremath{\Upsilon}}(4S)$ resonance. We measure the overall branching fraction and $CP$ asymmetry to be $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{K}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0})=(31.8\ifmmode\pm\else\textpm\fi{}1.8\ifmmode\pm\else\textpm\fi{}2.{1}_{\ensuremath{-}0.0}^{+6.0})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and ${A}_{CP}({B}^{+}\ensuremath{\rightarrow}{K}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0})=0.07\ifmmode\pm\else\textpm\fi{}0.05\ifmmode\pm\else\textpm\fi{}0.0{3}_{\ensuremath{-}0.03}^{+0.02}$, where the uncertainties are statistical, systematic, and due to the signal model, respectively. This is the first measurement of the branching fraction for ${B}^{+}\ensuremath{\rightarrow}{K}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}$. We find first evidence of a $CP$ asymmetry in ${B}^{+}\ensuremath{\rightarrow}{K}^{*}(892{)}^{+}{\ensuremath{\pi}}^{0}$ decays: ${A}_{CP}({B}^{+}\ensuremath{\rightarrow}{K}^{*}(892{)}^{+}{\ensuremath{\pi}}^{0})=\ensuremath{-}0.52\ifmmode\pm\else\textpm\fi{}0.14\ifmmode\pm\else\textpm\fi{}0.0{4}_{\ensuremath{-}0.02}^{+0.04}$. 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.

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