Measurement of the B(s)(0)-(B)over-bar(s)(0) 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).