Implications of the Fleischer-Mannel bound

Fleischer and Mannel (FM) have shown that it may become possible to constrain the angle gamma of the unitarity triangle from measurements of various B --> pi K decays, This constraint is independent of hadronic uncertainties to the few percent level. We show that, within the Standard Model, the FM bound can give strong constraints on the CKM parameters. In particular, it could predict a well-defined sign for sin 2 gamma and sin 2 alpha. In a class of extensions of the Standard Model, where New Physics affects only Delta B = 2 (and, in particular, not Delta B = 1) processes, the FM bound can lead to constraints on CP asymmetries in B decays into final CP eigenstates even if B - (B) over bar mixing is dominated by unknown New Physics. In our analysis, we use a new method to combine in a statistically meaningful way the various measurements that involve CKM parameters, (C) 1998 Elsevier Science B.V.