Title: Evidence for an Anomalous Like-sign Dimuon Charge Asymmetry


I will report on the measurement of the charge asymmetry A=(N++ - N--)/(N++ + N--) of like-sign dimuon events in 6.1 fb-1 of proton-antiproton collisions recorded with the D0 detector at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. From the charge asymmetry A we extract the asymmetry for semileptonic b-hadron decays A^b_sl=(-0.00957 +/- 0.00251 (stat) +/- 0.00146 (syst)). This measurement differs by 3.2 standard deviations from the standard model prediction A^b_sl(SM)=(-2.3 +/-0.6)*10^-4, and provides first evidence of anomalous CP violation in the mixing of neutral B mesons.