Measurement of the CP Violation Parameter A _Γ in D⁰ →k⁺K^- and D⁰ →π⁺π^- Decays

Asymmetries in the time-dependent rates of D0→K+K-and D0→π+π-decays are measured in a pp collision data sample collected with the LHCb detector during LHC Run 1, corresponding to an integrated luminosity of 3 fb-1. The asymmetries in effective decay widths between D0 and D-0 decays, sensitive to indirect CP violation, are measured to be AΓ(K+K-)=(-0.30±0.32±0.10)×10-3 and AΓ(π+π-)=(0.46±0.58±0.12)×10-3, where the first uncertainty is statistical and the second systematic. These measurements show no evidence for CP violation and improve on the precision of the previous best measurements by nearly a factor of two.