Form factors of semileptonicDdecays from QCD sum rules

We give a detailed QCD sum-rule analysis of the semileptonic decays $D^{+}\to {\overline{K}}^0{e}^{+}{\nu }_e$ and $D^{+}\to {\overline{K}}^{0*}{e}^{+}{\nu }_e$. We use the standard method based on expansion in Euclidean distance as well as a new set of sum rules on the light cone. We compare the results with current experimental data and results from quark models. Special attention is paid to the $t$ dependence of the form factors. We find from our sum-rule analysis that for the vector form factors the usual pole model approximation works perfectly well, but is not adequate for the axial-vector form factors.