Measurement of the $B_s^0\to J/\psi K_S^0$ branching fraction
  The $B_s^0\to J/\psi K_S^0$ branching fraction is measured in a data sample corresponding to 0.41$fb^{-1}$ of integrated luminosity collected with the LHCb detector at the LHC. This channel is sensitive to the penguin contributions affecting the sin2$\beta$ measurement from $B^0\to J/\psi K_S^0$ The time-integrated branching fraction is measured to be $BF(B_s^0\to J/\psi K_S^0)=(1.83\pm0.28)\times10^{-5}$. This is the most precise measurement to date. 
LHCb collaboration: R. Aaij, C. Abellan Beteta, B. Adeva, M. Adinolfi,   C. Adrover, A. Affolder, Z. Ajaltouni, J. Albrecht,...
hep-ex