The D0 Collaboration has measured the like-sign dimuon charge asymmetry in $p\overline{p}$ 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, namely, $CP$ violation in interference of decays of $B^0$ with and without mixing to flavor nonspecific states $f_i$, followed by the decay $f_i\to \mu X$. The discrepancy between the D0 measurement and the standard model expectation is reduced to less than 3 standard deviations.

• Received 1 March 2013

DOI:https://doi.org/10.1103/PhysRevD.87.074020