Lifetime differences, direct CP violation, and partial widths in D⁰ meson decays to K⁺K^- and π⁺ π^-

We describe several measurements using the decays D⁰→K⁺K^- and π⁺π^-. We find the ratio of partial widths, Γ(D⁰→K⁺K^-)/Γ (D⁰→π⁺π^-), to be 2.96±0.16±0.15, where the first error is statistical and the second is systematic. We observe no evidence for direct CP violation, obtaining A_CP(KK)=(0.0±2.2±0.8)% and A_CP(ππ)=(1.9±3.2±0.8)%. In the limit of no CP violation we measure the mixing parameter y_CP=-0.012±0.025±0.014 by measuring the lifetime difference between D⁰→K⁺K^- or π⁺ π^- and the CP neutral state, D⁰→K^-π⁺. We see no evidence for mixing.