Measurements of Indirect CP Asymmetries in D[superscript 0] → K[superscript −K[superscript +] and D[superscript 0] → π[superscript −]π[superscript +] Decays

A study of indirect CP violation in D[superscript 0] mesons through the determination of the parameter A[subscript Γ] is presented using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0 fb[superscript −1], collected with the LHCb detector and recorded at the center-of-mass energy of 7 TeV at the LHC. The parameter A[subscript Γ] is the asymmetry of the effective lifetimes measured in decays of D[superscript 0] and [¯ over D][superscript ​0] mesons to the CP eigenstates K[superscript −]K[superscript +] and π[superscript −]π[superscript +]. Fits to the data sample yield A[subscript Γ](KK) = (−0.35±0.62±0.12) × 10[superscript −3] and A[subscript Γ](ππ) = (0.33±1.06±0.14) × 10[superscript −3], where the first uncertainties are statistical and the second systematic. The results represent the world’s best measurements of these quantities. They show no difference in A[subscript Γ] between the two final states and no indication of CP violation.