LIMITATIONS IN MEASURING THE ANGLE-BETA BY USING SU(3) RELATIONS FOR B-MESON DECAY AMPLITUDES

Flavour SU(3) symmetry of strong interactions and certain dynamical assumptions have been used in a series of recent publications to extract weak CKM phases from B-decays into {pi pi, pi K, K ($) over bar K} final states. We point out that irrespectively of SU(3)-breaking effects the presence of QCD-penguin contributions with internal u- and c-quarks precludes a clean determination of the angle beta in the unitarity triangle by using the branching ratios only. This difficulty can be overcome by measuring in addition the ratio x(d)/x(s) of B-d(0) - ($) over bar B-d(0) to B-s(0) - ($) over bar B-s(0) mixings. The measurement of the angle gamma is unaffected by these new contributions. Some specific uncertainties related to SU(3)-breaking effects and electroweak penguin contributions are briefly discussed.