New Aspects of $B\to\pi\pi, \pi K$ and their Implications for Rare Decays

We analyse the B -> pi pi, pi K modes in the light of the most recent B-factory data, and obtain the following new results: (i) the B0 -> pi+ pi-, pi- K+ modes prefer gamma=(74+-6)deg, which - together with |V_ub/V_cb| - allows us to determine the ``true'' unitarity triangle and to search for CP-violating new-physics contributions to B0_d-\bar B0_d mixing; (ii) the B -> pi K puzzle reflected in particular by the low experimental value of the ratio R_n of the neutral B -> pi K rates persists and still favours new physics in the electroweak penguin sector with a new CP-violating phase phi ~ -90deg, although now also phi ~ +90deg can bring us rather close to the data; (iii) the mixing-induced B0 -> pi0 K_S CP asymmetry is a sensitive probe of the sign of this phase, and would currently favour phi ~ +90deg, as well as the direct CP asymmetry of B+- -> pi0 K+-, which suffers, however, from large hadronic uncertainties; (iv) we investigate the sensitivity of our B -> pi K analysis to large non-factorizable SU(3)-breaking effects and find that their impact is surprisingly small so that it is indeed exciting to speculate on new physics; (v) assuming that new physics enters through Z0 penguins, we study the interplay between B -> pi K and rare B, K decays and point out that the most recent B-factory constraints for the latter have interesting implications, bringing us to a few scenarios for the future evolution of the data, where also the mixing-induced CP violation in B0 -> pi0 K_S plays a prominent role.