Measurements of indirect CP asymmetries in D0 → K- K+ and D0 → π- π+ decays.

A study of indirect CP violation in D-0 mesons through the determination of the parameter A(Gamma) is presented using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0 fb(-1), collected with the LHCb detector and recorded at the center-of-mass energy of 7 TeV at the LHC. The parameter A(Gamma) is the asymmetry of the effective lifetimes measured in decays of D-0 and (D) over bar (0) mesons to the CP eigenstates K-K+ and pi(-)pi(+). Fits to the data sample yield A(Gamma)(KK) = (-0.35 +/- 0.62 +/- 0.12) x 10(-3) and A(Gamma)(pi pi) = (0.33 +/- 1.06 +/- 0.14) x 10(-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(Gamma) between the two final states and no indication of CP violation.