Measurement of the Semileptonic CP Asymmetry in B0-¯B0 Mixing

Abstract

The semileptonic C P asymmetry in B 0 - ¯ B 0 mixing, a d sl , is measured in proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb − 1 , recorded by the LHCb experiment. Semileptonic B 0 decays are reconstructed in the inclusive final states D − μ + and D * − μ + , where the D − meson decays into the K + π − π − final state and the D * − meson into the ¯ D 0 ( → K + π − ) π − final state. The asymmetry between the numbers of D ( * ) − μ + and D ( * ) + μ − decays is measured as a function of the decay time of the B 0 mesons. The C P asymmetry is measured to be a d sl = ( − 0.02 ± 0.19 ± 0.30 ) % , where the first uncertainty is statistical and the second systematic. This is the most precise measurement of a d sl to date and is consistent with the prediction from the standard model.