We report a measurement of the CP violating asymmetry in $D^0topi^+pi^-$ decays using approximately 215,000 decays reconstructed in about $5.94$ fb$^{-1}$ of CDF data. We use the strong $D^{star +}to D^0pi^+$ decay ($D^{star}$ tag) to identify the flavor of the charmed meson at production time and exploit CP-conserving strong $cbar{c}$ pair-production in $pbar{p}$ collisions. Higher statistic samples of Cabibbo-favored $D^0to K^-pi^+$ decays with and without $D^{star}$ tag are used to highly suppress systematic uncertainties due to detector effects. The result, $Acp(D^0 to pi^{+}pi^{-}) = bigl[0.22pm0.24statpm0.11systbigr]%$, is the worlds most precise measurement to date and it is fully consistent with no CP violation.
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