Measurement of D0-D̄0 mixing using the ratio of lifetimes for the decays D0→K-π+, K-K+, and π-π+

We present a measurement of D0-D̄0 mixing parameters using the ratios of lifetimes extracted from a sample of D0 mesons produced through the process D*+→D0π+, which decay to K-π+, K-K+, or π-π+. The lifetimes of the CP-even, Cabibbo-suppressed modes K-K+ and π-π+ are compared with that of the CP-mixed, Cabibbo-favored mode K-π+ to obtain a measurement of yCP, which in the limit of CP conservation corresponds to the mixing parameter y. The analysis is based on a data sample of 384fb-1 collected by the BABAR detector at the PEP-II asymmetric-energy e+e- collider. We obtain yCP=[1.24±0.39(stat)±0.13(syst)]%, which is evidence for D0-D̄0 mixing at the 3σ level, and ΔY=[-0.26±0.36(stat) ±0.08(syst)]%, where ΔY constrains possible CP violation. Combining this result with a previous BABAR measurement of yCP obtained from a separate sample of D0→K-K+ events, we obtain yCP=[1.03±0.33(stat)±0. 19(syst)]%.