Implications of large dimuon CP asymmetry in B_d,s decays on minimal flavor violation with low tan β

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 tanβ = ν_u/ν_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 √tanβ. The effect is universal in the B_s and B _d systems, leading to S_ψk ∼ sin 2β-0.15 and S_ψφ ∼ 0.25. The effects on ∈K and on electric dipole moments are negligible. The most plausible mechanism is tree-level scalar exchange. MFV supersymmetry with low tanβ will be excluded. Finally, we explain how a pattern of deviations from the Standard Model predictions for S_ψφ, S_ψk and ∈K can be used to test MFV and, if MFV holds, to probe its structure in detail.