Mixing-induced CP violation in the decay Bd→K0 K̄0

Recently, flavour SU (3) symmetry of strong interactions has been combined with certain dynamical assumptions to derive triangle relations among B-meson decay-amplitudes. We show that these relations allow a prediction of the mixing-induced CP asymmetry ACPmix-ind (Bd→K0K̄0). Contrary to statements made in several previous papers, this asymmetry should be non-vanishing in the Standard Model due to QCD-penguins with internal up- and charm-quark exchanges and could be as large as O (30%). The branching ratio BR (Bd→K0K̄0) is expected to be of O (10−6). In the future, the results presented in this letter should allow interesting tests of the SU (3) triangle relations and of the Standard Model description of CP violation.