Cascade Mixing and the CP-Violating Angle Beta

In the decay chain B(d) --> Psi + K --> Psi + (pi l nu), neutral K mixing follows on the heels of neutral B mixing. This “cascade mixing” leads to an interference which probes cos(2beta), where beta is one of the three CP-violating phase angles which characterize CP violation in the Standard Model. Widely-discussed future B-system experiments will determine trigonometric functions of these three phase angles, leaving the underlying angles themselves discretely ambiguous. A determination of cos(2beta) through cascade mixing would eliminate all the discrete ambiguities entirely.