J/ψ hadron interaction in vacuum and in QGP

Motivated by the recent lattice data that J/ψ will survive up to 1.6T_c, we calculate the thermal width of J/ψ at finite temperature in perturbative QCD. The inputs of the calculation are the parton quarkonium dissociation cross sections at the NLO in QCD, which were previously obtained by Song and Lee, and a Gaussian charmonium wavefunction, whose size was fitted to an estimate by Wong by solving the Schrödinger equation for charmonium in a potential extracted from the lattice at finite temperature. We find that the total thermal width above 1.4T_c becomes larger than 100 to 200 MeV, depending on the effective thermal masses of the quark and gluon, which we take it to vary from 600 to 400 MeV.