Calculations of penguin diagrams in B decays

We analyze the effects of the space-like penguin diagrams in two-body B decays B− → K−K0 and B− → π−K0. Special attention is paid to the operator Q6, whose contribution is large in the BSW model, but vanishes in the PQCD method in the approximation of neglecting the masses in the final states. Suppressions of the space-like penguin diagrams are found in the PQCD method, which implies that the contributions of the space-like penguins are small compared to those of the time-like penguins.