Heavy quarkonia and quark drip lines in quark–gluon plasma

Using the potential model and thermodynamical quantities obtained in lattice gauge calculations, we determine the spontaneous dissociation temperatures of colour-singlet quarkonia and the ‘quark drip lines’ which separate the region of bound quarkonium states from the unbound region. The dissociation temperatures of J /ψ and χ b in quenched QCD are found to be 1.62 T c and 1.18 T c respectively, in good agreement with spectral function analyses. The dissociation temperature of J /ψ in full QCD with two flavours is found to be 1.42 T c . For possible bound quarkonium states with light quarks, the characteristics of the quark drip lines severely limit the stable region close to the phase transition temperature. Bound colour-singlet quarkonia with light quarks may exist very near the phase transition temperature if their effective quark mass is of the order of 300–400 MeV.