Extracting γ from Bs(d)→J/ψKS and Bd(s)→D+d(s)D-d(s)

A completely general parametrization of the time-dependent decay rates of the modes Bs→J/ψKS and Bd→J/ψKS 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 Bs→J/ψKS observables probe the angle γ of the unitarity triangle. Using the U-spin symmetry, the overall normalization of the Bs→J/ψKS rate can be fixed with the help of the CP-averaged Bd→J/ψKS rate, providing a new strategy to determine γ. This extraction of γ 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 β from Bd→J/ψKS, 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 Bd→D+D- rate, if its overall normalization is fixed through the CP-averaged Bs→D+sD-s rate. (orig.)