J/ψ hadron interaction in vacuum and in QGP

I first discuss the NLO QCD calculation for the dissociation cross section of J/ψ into open charm, which shows a large second order correction near the threshold. The large correction softens when effective thermal masses in the order of the binding energy are introduced for the quarks and gluons. Hence, with the thermal masses, the method is reliably applied to calculate the dissociation cross section of J/ψ, which according to recent lattice results seems to remain bound even up to 1.6 × T_c. The dominant contribution to the dissociation comes from the thermal gluons, while the effects due to thermal quarks are suppressed due to suppressed phase space. The relevance of this result is discussed in the context of RHIC and signature of QGP.