Understanding the like-sign dimuon charge asymmetry in $p bar{p}$ collisions

The DO collaboration has measured the like-sign dimuon charge asymmetry in $p bar{p}$ collisions at the Fermilab Tevatron collider. The result is significantly different from the standard model expectation of CP violation in mixing. In this paper we consider the possible causes of this asymmetry and identify one standard model source not considered before. It decreases the discrepancy of the like-sign dimuon charge asymmetry with the standard model prediction, although does not eliminate it completely.