Measurement of the B0(s) - anti-B0(s) Oscillation Frequency

We present the first precise measurement of the B-s(0)-(B) over bar (0)(s) oscillation frequency Delta m(s). We use 1 fb(-1) of data from p (p) over bar collisions at root s=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The sample contains signals of 3600 fully reconstructed hadronic B-s decays and 37 000 partially reconstructed semileptonic B-s decays. We measure the probability as a function of proper decay time that the B-s decays with the same, or opposite, flavor as the flavor at production, and we find a signal consistent with B-s(0)-(B) over bar (0)(s) oscillations. The probability that random fluctuations could produce a comparable signal is 0.2%. Under the hypothesis that the signal is due to B-s(0)-(B) over bar (0)(s) oscillations, we measure Delta m(s)=17.31(-0.18)(+0.33)(stat)+/- 0.07(syst) ps(-1) and determine vertical bar V-td/V-ts vertical bar=0.208(-0.002)(+0.001)(expt)(-0.006)(+0.008)(theor).