The D0 collaboration has recently announced evidence for a dimuon CP asymmetry in B_{ d,s} decays of order one percent. If confirmed, this asymmetry requires new physics. We argue that for minimally flavor violating (MFV) new physics, and at low tan beta=v_u/v_d, there are only two four-quark operators (Q_{ 2,3}) that can provide the required CP violating effect. The scale of such new physics must lie below 260 GeV sqrt{ tan beta}. The effect is universal in the B_s and B_d systems, leading to S_{ psi K}~sin(2beta)-0.15 and S_{ psi phi}~0.25. The effects on epsilon_K and on electric dipole moments are negligible. The most plausible mechanism is tree-level scalar exchange. MFV supersymmetry with low tan beta will be excluded. Finally, we explain how a pattern of deviations from the Standard Model predictions for S_{ psi phi}, S_{ psi K} and epsilon_K can be used to test MFV and, if MFV holds, to probe its structure in detail.
Categories: hep-ph