we explore below it is sufficient to consider products of vector and/or axial vector currents only. We define a basis of such operators by $$\begin{aligned}
\label{basis}
   O_1^q &=& (\bar b_\alpha s_\alpha)_{V-A}\,
    (\bar q_\beta q_\beta)_{V+A} \,, \qquad
    O_2^q = (\bar b_\alpha s_\beta)_{V-A}\,
    (\bar q_\beta q_\alpha)_{V+A} \,, \nonumber\\
   O_3^q &=& (\bar b_\alpha s_\alpha)_{V-A}\,
    (\bar q_\beta q_\beta)_{V-A} \,, \qquad
    O_4^q = (\bar b_\alpha s_\beta)_{V-A}\,
    (\bar q_\beta q_\alpha)_{V-A} \,, \nonumber\\
   O_5^q &=& (\bar b_\alpha q_\alpha)_{V-A}\,
    (\bar q_\beta s_\beta)_{V+A} \,, \qquad
    O_6^q = (\bar b_\alpha q_\beta)_{V-A}\,
    (\bar q_\beta s_\alpha)_{V+A} \,,\end{aligned}$$ and denote their Wilson coefficients by $c_i^q$. We implicitly assume a regularization scheme that preserves Fierz identities. In a general model, we also need operators of opposite chirality compared to the ones shown above, i.e., with $V-A\leftrightarrow 
V+A$ everywhere. We denote these operators by $\widetilde O_i^q$ and their coefficients by $\widetilde c_i^q$. Thus, the most general penguin Hamiltonian considered in this paper takes the form $$\label{Hpeng}
   {\cal H}_{\rm peng} = \frac{G_F}{\sqrt 2}\,\sum_i 
   \sum_q \left[ c_i^q(\mu)\,O_i^q(\mu)
   + \widetilde c_i^q(\mu)\,\widetilde O_i^q(\mu) \right] .$$ To this, one has to add the current–current operators in (\[curcur\]) and the chromo-magnetic dipole operator. It is implicitly understood that for the cases where $q=s$ or $b$ the operators $O_5^q$ and $O_6^q$ as 