Studies of Asymmetries in Semileptonic B decays at LHCb

CP violating and CP conserving asymmetries in semileptonic B decays are studied with the LHCb detector using a data sample corresponding to an integrated luminosity of 1 fb 1 of pp collisions at p s = 7 TeV, collected during the 2011 run of the LHC. The CP-violating, flavour specific asymmetry, A s fs is measured to be ( 0 : 06 0 : 50 stat : 0 : 36 sys : ) %, which is the most precise measurement of this quantity to date and agrees with the Standard Model prediction. The B 0 and B 0 s mixing frequencies are measured with high precision for the first time from semileptonic decays only and are found to be D m d = ( 0 : 503 0 : 011 stat : 0 : 013 sys : ) ps 1 and D m s = ( 17 : 93 0 : 22 stat : 0 : 15 sys : ) ps 1 , respectively.