Evidence for CP violation in time-integrated D⁰ → h^-h⁺ decay rates

A search for time-integrated CP violation in D ⁰ → h ^-h ⁺ (h = K, π) decays is presented using 0.62 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∗ ⁺ → D ⁰π ⁺ and D∗ ^- → D¯ ⁰π ^- decay chains. The difference in CP asymmetry between D ⁰ → K ^-K ⁺ and D ⁰ → π ^-π ⁺, ΔA _CP ≈ A _CP(K ^-K ⁺)-A _CP(π ^-π ⁺), is measured to be [-0.82 ± 0.21(stat) ± 0.11(syst)]%. This differs from the hypothesis of CP conservation by 3.5 standard deviations.