Observation of D0-D^̄0 oscillations

We report a measurement of the time-dependent ratio of D0→K ⁺π ^- to D0→K ^-π ⁺ decay rates in D* ⁺-tagged events using 1.0 fb ^-1 of integrated luminosity recorded by the LHCb experiment. We measure the mixing parameters x′2=(-0.9±1.3)×10 ^-4, y′=(7.2±2.4)×10 ^-3, and the ratio of doubly-Cabibbo-suppressed to Cabibbo-favored decay rates R _D=(3. 52±0.15)×10 ^-3, where the uncertainties include statistical and systematic sources. The result excludes the no-mixing hypothesis with a probability corresponding to 9.1 standard deviations and represents the first observation of D0-D ^̄0 oscillations from a single measurement.