well as $\widetilde O_5^q$ and $\widetilde O_6^q$ are omitted from the list of operators, because they are Fierz-equivalent to the remaining ones.

The QCD and electroweak penguin operators present in the effective weak Hamiltonian of the SM in(\[Heff\]) are linear combinations of the four operators $O_{1\dots 4}^q$. However, in a general model there may be additional penguin operators built out of $O_5^q$, $O_6^q$, and of the opposite-chirality operators $\widetilde O_i^q$. Also, there may be operators which cannot be represented as linear combinations of QCD and electroweak penguin operators as shown in (\[QCDp\]) and (\[EWp\]), because in a general model the flavor symmetry among up- or down-type quarks can be violated. An example would be operators with flavor content $\bar sb(\bar d d-\bar s s)$, which are absent in the SM. Because such operators are of no relevance to our discussion they will not be explored any further here. For completeness, we show how the Wilson coefficients $C_{3\dots 10}$ of the SM penguin operators in (\[Heff\]) can be expressed in terms of the coefficients $c_i^q$. Defining the linear combinations $$\label{cdefs}
   c_i^{\rm QCD} \equiv \frac{c_i^u+2c_i^d}{3} \,, \qquad
   c_i^{\rm EW} \equiv c_i^u-c_i^d \,,$$ we have $$\begin{aligned}
   -\lambda_t\,C_{3,4} &=& c_{3,4}^{\rm QCD} \,, \qquad
   -\lambda_t\,C_{5,6} 