Evidence forCPViolation in Time-IntegratedD0→h−h+Decay Rates

A search for time-integrated $CP$ violation in $D^0\to h^{-}{h}^{+}$ ($h=K$, $\pi$) decays is presented using $0.62{\mathrm{fb}}^{-1}$ of data collected by LHCb in 2011. The flavor of the charm meson is determined by the charge of the slow pion in the $D^{*+}\to D^0{\pi }^{+}$ and $D^{*-}\to {\overline{D}}^0{\pi }^{-}$ decay chains. The difference in $CP$ asymmetry between $D^0\to K^{-}{K}^{+}$ and $D^0\to {\pi }^{-}{\pi }^{+}$, $\Delta A_{CP}\equiv A_{CP}(K^{-}{K}^{+})-A_{CP}({\pi }^{-}{\pi }^{+})$, is measured to be $[-0.82\pm 0.21(\mathrm{stat})\pm 0.11(\mathrm{syst})]\%$. This differs from the hypothesis of $CP$ conservation by 3.5 standard deviations.