Evidence forD0−D¯0Mixing Using the CDF II Detector

We measure the time dependence of the ratio of decay rates for the rare decay $D^0\to K^{+}{\pi }^{-}$ to the Cabibbo-favored decay $D^0\to K^{-}{\pi }^{+}$. A signal of $12.7\times {10}^3$ $D^0\to K^{+}{\pi }^{-}$ decays was obtained using the Collider Detector at Fermilab II detector at the Fermilab Tevatron with an integrated luminosity of $1.5{\mathrm{fb}}^{-1}$. We measure the $D^0-{\overline{D}}^0$ mixing parameters $(R_D,y^{\prime },x^{\prime 2})$, and find that the data are inconsistent with the no-mixing hypothesis with a probability equivalent to 3.8 Gaussian standard deviations.