CP VIOLATION IN INCLUSIVE AND EXCLUSIVE CHARMLESS B-DECAYS

Absorptive parts in penguin amplitudes lead to CP-violating partial rate asymmetries in B-meson decays. A careful study of the inclusive process reveals a subtlety in the implementation of this mechanism. Because of (1) the smallness of V(ub)/V(cb), (2) the fact that alpha-s(m(b)) is not too small, and (3) the kinematic suppression of ccBAR absorptive contribution, O(alpha-s2) effects have to be kept consistently. We find a strong correlation between the CP rate asymmetries of the b --> suuBAR mode and the purely loop-induced b --> sddBAR and sssBAR modes, which is a consequence of the constraints of CPT invariance. The semi-inclusive charmless b --> suuBAR decay rate asymmetry is therefore negligibly small. With the (semi-)inclusive result as a guide, we estimate the rates and CP asymmetries for several exclusive modes. Keeping only the perturbative, penguin-induced absorptive part, one finds that the modes due to b --> suuBAR (e.g., B- --> K- pi-0) could have CP rate asymmetries opposite in sign with respect to pure penguin modes (such as B- --> K- phi), contrary to naive expectations. Charmless b --> d transitions are also discussed. We emphasize that exclusive b --> d modes (such as B- --> K- K(S)) may be more promising for CP studies within the standard model. Many uncertainties and problems related to penguin processes are discussed and assessed in detail.