Something about Z-penguins I want to tell

The effects of new heavy particles appearing in extensions of the standard model (SM) can be accounted for at low energies in terms of effective operators. The unprecedented accuracy reached by the electroweak (EW) precision measurements performed at the high-energy colliders LEP and SLC impose stringent constraints on the coefficients of the operators entering the EW sector. Other severe constraints came in recent years from the BaBar, Belle, CDF, and DØ experiments and concern extra sources of flavor and CP violation that represent a generic problem in many beyond the SM (BSM) scenarios. The most pessimistic but experimentally well supported solution to the flavor puzzle is to assume that all flavor and CP violation is governed by the known structure of the SM Yukawa interactions. In these minimal flavor violating (MFV) [1, 2] models, correlations between certain flavor diagonal high-energy and flavor off-diagonal low-energy observables exist since, by construction, BSM physics couples dominantly to the third generation. To simplify matters, we restrict ourselves in the following to scenarios that involve only SM operators, so-called constrained MFV (CMFV) [3] models, and thus consider only left-handed currents. Correlations between flavor diagonal and off-diagonal amplitudes, similar to the ones discussed below, might exist in many beyond-MFV scenarios in which the modification of the flavor structure is non-universal. One example for such a correlation is provided by the intimate relation between the b → sZ and Z → bb̄ amplitude [4] present in the original RandallSundrum scenario [5].