CP-tagged charm decays: relevance, status and prospects

The analysis of quantum-correlated $D-\bar{D}$ decays produced at the $\psi (3770)$ resonance gives unique insight into quantities such as strong-phase differences and coherence factors. Knowledge of these parameters is invaluable for measurements of the CKM-angle $\gamma$ (${\varphi }_3$) in $B \to DK$decays\mathrm{.}ResultsfromCLEO-canalysesperformedatthe$\psi(3770)$ resonance in a variety of decay channels are reported, and their consequences for the determination of $\gamma$ is assessed. Future prospects are given for extensions to the present studies.