Measurement of the B^0_s - \bar{B}^0_s oscillation frequency Delta m_s   in B^0_s -> D_s^-(3) pi decays
  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}. 
LHCb Collaboration: R. Aaij, C. Abellan Beteta, B. Adeva, M. Adinolfi,   C. Adrover, A. Affolder, Z. Ajaltouni, J. Albrecht,...
hep-ex