Precision measurement of the oscillation frequency in the $B_{s}^{0}-\bar{B}_{s}^{0}$ system

A measurement of the B 0 s { B 0 s oscillation frequency, which is equivalent to the mass difference m s of the B 0 s mass eigenstates, is presented. Using a dataset, corresponding to an integrated luminosity of 1.0 fb 1 , collected by the LHCb experiment at the LHC in 2011, a total of about 34,000 B 0 s ! D s + signal candidates are reconstructed. The average decay time resolution is 44 fs and the effective tagging efficiency in this channel is " e = 3 : 5%. The oscillation frequency is measured to be m s = 17.768 0.023 (stat) 0.006 (syst) ps 1 , which is the most precise measurement to date