Penguin topologies, rescattering effects and penguin hunting with Bu,d→K(K)over-bar and B±→π± K

In the recent literature, constraints on the CKM angle gamma arising from the branching ratios for B+/- --> pi(+/-)K and B-d --> pi(-/+)K(+/-) decays received a lot of attention. An important theoretical limitation of the accuracy of these bounds is due to rescattering effects, such as B+ --> {pi(0)K(+)} --> pi(+)K(0). We point out that these processes are related to penguin topologies with internal up-quark exchanges and derive SU(2) isospin relations among the B+ --> pi(+)K(0) and B-d(0) --> pi(-)K(+) decay amplitudes by defining "tree" and "penguin" amplitudes in a proper way, allowing the derivation of generalized bounds on the CKM angle gamma. We propose strategies to obtain insights into the dynamics of penguin processes with the help of the decays B-u,B-d --> K (K) over bar and B+/- --> pi(+/-)K, derive a relation among the direct CP-violating asymmetries arising in these modes, and emphasize that rescattering effects can be included in the generalized bounds on gamma completely this way. Moreover, we have a brief look at the impact of new physics. (C) 1998 Elsevier Science B.V.