J/ψ at finite density in QCD sum rule analysis

For the "anomalous" J/psi suppression in Pb-Pb collision announced by NA50 Collaboration I propose new mechanism accessible to the novel behavior of the data. The point of new idea is to focus on in-medium effects on the masses of mesons containing charmed quarks. In QCD sum rule analysis, I find that the D-meson involving one charmed quark feels more attractive force from the surrounding nucleons than the charmonium composed of two charmed quarks. As a result, it will appear that as the nucleon density increases D (D) over bar threshold in turn falls below higher lying charmonium states (psi',chi(c)) which have the energy levels below the threshold in vacuum. Finally, also for the low-lying J/psi state, a larger decay channel to the threshold could be opened up. Therefore, this mechanism can qualitatively explain some features of the anomalous J/psi suppression without advent of deconfinement phase.