Observation of – Oscillations

We report the observation of oscillations using 1 fb−1 of data from collisions with the CDF II detector at the Fermilab Tevatron. We measure the probability, as a function of proper decay time, that the decays with the same, or opposite, flavor as its flavor at production, which is determined using opposite-side and same-side flavor identification methods. We find a signal consistent with oscillations, with a significance greater than 5σ. We measure Δms=17.77±0.10(stat)±0.07(syst)ps−1.