Observation of $B_s^0-\bar{B}_s^0$ Oscillations and Measurement of $\Delta m_s$ in CDF

Abstract

We report the observation of $\B_s^0-\bar{B}_s^0$ oscillations performed by the CDF II detector using a data sample of 1 $fb^{-1}$ of $p\bar{p}$ collisions at $\sqrt{s}=1.96 \TeV$. 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 $\B_s^0-\bar{B}_s^0$ oscillations. The probability that random fluctuations could produce a comparable signal is $8 \times 10^{-8}$, which exceeds $5\sigma$ significance. We measure $\Delta m_s = 17.77 \pm{0.10} ({\rm stat}) \pm{0.07} ({\rm syst}) ps^{-1}$. A very important update has been presented by the CDF collaboration after I gave my talk, the latest available results on $B_s$ mixing are included here.