Observation of B0s−B¯0s Oscillations

We report the observation of B(s)(0)-(B) over bar (0)(s) oscillations from a time-dependent measurement of the B(s)(0)-(B) over bar (0)(s) oscillation frequency Delta m(s). Using a data sample of 1 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron, we find signals of 5600 fully reconstructed hadronic B(s) decays, 3100 partially reconstructed hadronic B(s) decays, and 61 500 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 for B(s)(0)-(B) over bar (0)(s) oscillations. The probability that random fluctuations could produce a comparable signal is 8x10(-8), which exceeds 5 sigma significance. We measure Delta m(s)=17.77 +/- 0.10(stat)+/- 0.07(syst) ps(-1) and extract vertical bar V(td)/V(ts)vertical bar=0.2060 +/- 0.0007(Delta m(s))(-0.0060)(+0.0081)(Delta m(d)+theor). RI Ruiz, Alberto/E-4473-2011; Robson, Aidan/G-1087-2011; De Cecco, Sandro/B-1016-2012; St.Denis, Richard/C-8997-2012; Prokoshin, Fedor/E-2795-2012; Azzi, Patrizia/H-5404-2012