D mesons in matter and the in-medium properties of charmonium

We study the changes in the partial decay widths of excited charmonium states into DD, when the D-meson mass decreases in nuclear matter, taking the internal structure of the hadrons into account. Calculations within the 3P0 model for ψ(3686) and ψ(3770) imply that naive estimates of the in-medium widths based only on phase space are grossly exaggerated. Due to nodes in the wave functions, these states may even become narrow at high densities, if the D-meson mass is decreased by about 200 MeV. For the χ states, we generally expect stronger modifications of the widths. The relevance of the χ widths for J/ψ suppression in heavy ion collision is discussed. These phenomena could be explored in experiments at the future accelerator facility at GSI.