Hints for new sources of flavour violation in meson mixing

The recent results by the Fermilab-Lattice and MILC collaborations on the hadronic matrix elements entering B-d,B- s- (B) over bar (d, s) mixing show a significant tension of the measured values of the mass differences Delta M-d,M- s with their SM predictions. We review the implications of these results in the context of Constrained Minimal Flavour Violation models. In these models, the CKM elements gamma and vertical bar V-ub vertical bar/vertical bar V-cb vertical bar can be determined from B-d,B- s- (B) over bar (d, s) mixing observables, yielding a prediction for gamma below its tree-level value. Determining subsequently vertical bar V-cb vertical bar from the measured value of either Delta Ms or epsilon(K) gives inconsistent results, with the tension being smallest in the Standard Model limit. This tension can be resolved if the flavour universality of new contributions to Delta F = 2 observables is broken. We briefly discuss the case of U(2)(3) flavour models as an illustrative example.