Open Questions in Charm Decays Deserving an Answer

A list is given of those open questions concerning the dynamics of charm decays where there exists a strong need for an answer. Such a need is based on lessons to be learnt about QCD – either in their own right or for a better understanding of $B$ physics – or on searches for New Physics with a small background from the Standard Model. The major items on this list are: lifetimes of the ${\mathrm{\Xi }}_c^{0,+}$ baryons; semileptonic branching ratios of $D_s$, $\Lambda _c$and$\Xi _c$ hadrons and absolute branching ratios for those states; radiative decays $D\rightarrow \gamma K^,, \gamma \rho /\omega , , D_s \rightarrow \gamma \phi /\omega ,, D\rightarrow l^+l^-K/K^$;$D^0-\bar D^0$oscillationsdowntoasensitivitybelow$10^{-4}$ and CP asymmetries in non-leptonic $D$ decays down to 0.1%. Ongoing and already approved experiments will produce important new insights, which are unlikely to provide sufficient answers to all these questions yet. It is discussed how a third-generation fixed-target experiment like CHARM2000 or a $\tau$-charm factory can fill the bill.