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where the c$_{ij}$ are dimensionless couplings. The condition |A Δ F =2 NP | < |A Δ F =2 SM | implies 

The strong bounds on Λ for generic c$_{ij}$ of order 1 is a manifestation of what in many specific frameworks (supersymmetry, technicolor, etc.) goes under the name of flavor problem : if we insist that the new physics emerges in the TeV region, we have to conclude that it possesses a highly non-generic flavor structure. 

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(ii) In the case of B$_{d}$ – B$_{d}$ and K $^{0}$– K 0 mixing, where both CP conserving and CP-violating observables are measured with excellent accuracy, there is still room for a sizable NP contribution (relative to the SM one), provided that it is to a good extent aligned in phase with the SM amplitude [ O (0 . 01) for the K system and O (0 . 3) for the B$_{d}$ system]. This is because the theoretical errors in the observables used to constraint the phases, S$_{B}$$_{d}$$_{→}$$_{ψK}$ and ϵ$_{K}$ , are smaller with respect to the theoretical uncertainties in Δ m$_{B}$$_{d}$ and Δ m$_{K}$ , which constrain the magnitude of the mixing amplitudes. 

(iii) In the case of B$_{s}$ – B$_{s}$ mixing, the precise determination of Δ m$_{B}$$_{s}$ does not allow large deviations in modulo with respect to the SM. The constraint is particularly severe if we consider the ratio Δ m$_{B}$$_{d}$/ Δ m$_{B}$$_{s}$ , where hadronic uncertainties cancel to a large extent. However, the constraint on the CP-violating phase is quite poor. Present data from CDF [13] and D0 [14] indicate a large 

