Comment on new physics contributions to Γ12s

A recent measurement by the D0 Collaboration finds a like-sign di-muon charge asymmetry in the B system that is roughly 3σ larger than the value predicated by the Standard Model. This suggests new physics contributing to B−B¯ mixing. For the current central value of the CP asymmetry, the required size of Γ12s is larger than the Standard Model estimate. In this Letter, we will explore the constraints on new physics contributions to Γ12s. We find that all but two dimension six operators of Standard Model fields are excluded from contributing an O(1) amount to Γ12s due to bounds from B decays. We argue that a more precise measurement of τ(Bs)/τ(Bd), which is possible with currently available data, could either support or strongly constrain the existence of new physics in Γ12s.