Quick introduction to lattice QCD, maximum entropy method, and hadron spectral functions above the deconfinement phase transition

We explain the basic principles in lattice gauge theory and the maximum entropy method (MEM), in particular emphasizing the importance of extrapolations in lattice gauge simulations and error analysis in the MEM analysis. Then, we analyse correlation functions of charmonia at finite temperature (T) on 323x (32-96) anisotropic lattices by MEM. It is shown that J/ψ and ηc survive as distinct resonances in the plasma even up to T ≅ 1.6Tc and that they eventually dissociate between 1.6Tc and 1.7Tc (Tc is the critical temperature of deconfinement). This suggests that the deconfined plasma is non-perturbative enough to hold heavy-quark bound states. The importance of having sufficient number of temporal data points in the MEM analysis is also emphasized