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 DD̄, 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 x states, we generally expect stronger modifications of the widths. The relevance of the x 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.