  The B^0_s-\bar{B}^0_s oscillation frequency Delta m_s is measured with 36
pb^{-1} of data collected in pp collisions at \sqrt{s} = 7 TeV by the LHCb
experiment at the Large Hadron Collider. A total of 1381 B^0_s -> D_s^- \pi^+
and \B^0_s -> D_s^- pi^+ pi^- pi^+ signal decays are reconstructed, with
average decay time resolutions of 44 fs and 36 fs, respectively. An oscillation
signal with a statistical significance of 4.6 sigma is observed. The measured
oscillation frequency is Delta m_s = 17.63 \pm 0.11 (stat) \pm 0.02 (syst)
ps^{-1}.

High Energy Physics - Experiment