Charm mixing at LHCb

We report a measurement of the time-dependent ration of $D^0 \to K^{+} \pi^{-}$ to $D^0 \to K^{-}\pi^{+}$ decay rates in $D^{*+}$-tagged events using 1.0 fb$^{-1}$ of integrated luminosity recorded by the LHCb experiment. We measure the mixing parameters $x'^2$ = (-0.9 $\pm$ 1.3) x 10$^{-4}, y'$ = (7.2 $\pm$ 2.4) x 10$^{-3}$ and the ratio of doubly-Cabibbo-suppressed to Cabibbo-favored decay rates $R_D$ = (3.52 $\pm$ 0.15) x 10$^{-3}$. The result excludes the no-mixing hypothesis with a probability corresponding to 9.1 standard deviations and represents the first observation of charm mixing from a single measurement.