ELIMINATION OF PENGUIN CONTRIBUTIONS TO CP ASYMMETRIES IN B-DECAYS THROUGH ISOSPIN ANALYSIS

Isospin symmetry in B(d)0 --> pi+pi-, B(d)0 --> pi-0-pi-0, B+ --> pi+pi-0 has been shown to remove the theoretical uncertainty due to penguin diagrams in the predictions for CP asymmetries in these decays. We apply this method in a critical analysis to two other examples with a larger number of isospin-related processes, B --> pi-K and B --> pi-rho. It is shown that certain ambiguities in the determination of the weak phase alpha-remain in these cases due to the larger number of processes. As a consequence of this and of the larger accumulated experimental error, the determination of alpha-from these processes is expected to be less accurate than from B --> pi-pi.