Measurement of indirect CP-violating asymmetries in $D^0\to K^{+}{K}^{-}$ and $D^0\to {\pi }^{+}{\pi }^{-}$ decays at CDF

We report a measurement of the indirect CP-violating asymmetries ($A_{\mathrm{\Gamma }}$) between effective lifetimes of anticharm and charm mesons reconstructed in $D^0\to K^{+}{K}^{-}$ and $D^0\to {\pi }^{+}{\pi }^{-}$ decays. We use the full data set of proton-antiproton collisions collected by the Collider Detector at Fermilab experiment and corresponding to $9.7$~fb${}^{-1}$ of integrated luminosity. The strong-interaction decay $D^{\ast +}\to D^0{\pi }^{+}$ is used to identify the meson at production as $D^0$ or ${\bar{D}}^0$. We statistically subtract $D^0$ and ${\bar{D}}^0$ mesons originating from $b$-hadron decays and measure the yield asymmetry between anticharm and charm decays as a function of decay time. We measure $A_\Gamma (K^+K^-) = (-0.19 \pm 0.15 (stat) \pm 0.04 (syst))%$and$A_\Gamma (\pi^+\pi^-)= (-0.01 \pm 0.18 (stat) \pm 0.03 (syst))%$. The results are consistent with the hypothesis of CP symmetry and their combination yields $A_{\mathrm{\Gamma }}=(-0.12\pm 0.12)\mathrm{\%}$.