A precise measurement of the $B^0$ meson oscillation frequency
  The oscillation frequency, $\Delta m_d$, of $B^0$ mesons is measured using semileptonic decays with a $D^-$ or $D^{*-}$ meson in the final state, in a data sample of $pp$ collisions collected by the LHCb detector corresponding to an integrated luminosity of 3.0$\mbox{fb}^{-1}$. A combination of the two decay modes gives $\Delta m_d = (505.0 \pm 2.1 \pm 1.0) \rm \,ns^{-1}$, where the first uncertainty is statistical and the second is systematic. This is the most precise single measurement of this parameter. It is compatible with the current world average and has similar precision. 
LHCb collaboration: R. Aaij, C. Abell\'an Beteta, B. Adeva, M.   Adinolfi, A. Affolder, Z. Ajaltouni, S. Akar, J. Albrecht, ...
hep-ex