PENGUIN TOPOLOGIES, RESCATTERING EFFECTS AND PENGUIN HUNTING WITH B-U,B-D-]K(K)OVER-BAR AND B-+ --]PI(+/-) K/

In the recent literature, constraints on the CKM angle gamma arising f rom the branching ratios for B+/- --> pi(+/-)K and B-d --> pi(-/+)K(+/ -) decays received a lot of attention. An important theoretical limita tion of the accuracy of these bounds is due to rescattering effects, s uch as B+ --> {pi(0)K(+)} --> pi(+)K(0). We point out that these proce sses are related to penguin topologies with internal up-quark exchange s 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 insight s 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 amo ng the direct CP-violating asymmetries arising in these modes, and emp hasize that rescattering effects can be included in the generalized bo unds on gamma completely this way. Moreover, we have a brief look at t he impact of new physics. (C) 1998 Elsevier Science B.V.