Measurement of the CP Asymmetry in Bs0 - B s0 Mixing

© 2016 CERN. The CP asymmetry in the mixing of Bs0 and Bs0 mesons is measured in proton-proton collision data corresponding to an integrated luminosity of 3.0 fb-1, recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV. Semileptonic Bs0 and Bs0 decays are studied in the inclusive mode Dsμ±ν(-)μX with the Ds mesons reconstructed in the Kπ final state. Correcting the observed charge asymmetry for detection and background effects, the CP asymmetry is found to be asls=(0.39±0.26±0.20)%, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of asls to date. It is consistent with the prediction from the standard model and will constrain new models of particle physics.