Mixing-Induced CP Violation in the Decay $B_d\to K^0{\bar{K}}^0$ within the Standard Model

Abstract

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 $\text{acpmi}(B_d\to K^0{\bar{K}}^0)$. 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 $\text{order}(30\%)$. The branching ratio BR$(B_d\to K^0{\bar{K}}^0)$ is expected to be of $\text{order}(10^{-6})$. 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.

Comments: 13 pages (LaTeX) + 4 figures included, Munich Technical University preprint TUM-T31-76/94