Extracting from and
Theory Division, CERN, CH-1211 Geneva 23, Switzerland
Received: 24 March 1999 / Published online: 15 July 1999
A completely general parametrization of the time-dependent decay rates of the modes and is given, which are related to each other through the U-spin flavour symmetry of strong interactions. Owing to the interference of current-current and penguin processes, the observables probe the angle of the unitarity triangle. Using the U-spin symmetry, the overall normalization of the rate can be fixed with the help of the CP-averaged rate, providing a new strategy to determine . This extraction of is not affected by any final-state-interaction effects, and its theoretical accuracy is only limited by U-spin-breaking corrections. As a by-product, this strategy allows us to also take into account the penguin effects in the determination of from ,which are presumably very small, and to predict the direct CP asymmetry arising in this mode. An analogous strategy is provided by the time-dependent rate, if its overall normalization is fixed through the CP-averaged rate.