Observation of Bs - Bs Oscillations

We report the observation of Bs - Bs oscillations from a time-dependent measurement of the Bs - Bs oscillation frequency Δms. Using a data sample of 1 fb-1 of pp collisions at sqrt(s) = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron, we find signals of 5600 full reconstructed hadronic Bs decays, 3100 partially reconstructed hadronic Bs decays, and 61500 partially reconstructed semileptonic Bs decays. We measure the probability as a function or proper decay time the that Bs decays with the same, or opposite, flavor as the flavor at production, and we find a signal for Bs - Bs oscillations. The probability that random fluctuations could produce a comparable signal is 8x10-8, which exceeds 5σ significance. The results are as follows:

Δms  =  17.77  ± 0.10(stat)  ± 0.07(sys)

 =  0.2060  ± 0.0007(exp)  +0.0081
 - 0.0060 

This result has been published in PRL: PRL 97, 242003 2006.
This result supersedes the previous measurement set using 1 fb-1: PRL 97, 062003 2006.


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