The elastic scattering of gqq, gqq and gqq and the thermalization of quarkgluon matter are studied. According to Feynman diagrams at the tree level, squared amplitudes for the elastic gqq scattering and the elastic gqq scattering are derived in perturbative QCD. Transport equations including the squared amplitudes for the elastic gqq, gqq and gqq scattering are established. Corresponding to anisotropic gluon and quark distributions created in central Au-Au collisions at RHIC, solutions of the transport equations show that thermalization time of quark matter can be shortened by the elastic gqq, gqq and gqq scattering.

Meson-charmonium dissociation reactions governed by the quark interchange are studied with temperaturedependent quark potentials. Quark-antiquark relative-motion wave functions and masses of charmonia and charmed mesons are determined by the central spin-independent part of the potentials or by the central spinindependent part and a smeared spin-spin interaction. The prominent temperature dependence of the masses is found. Based on the potentials, the wave functions, and the meson masses, we obtain temperature-dependent cross sections for the fifteen dissociation reactions: πJ /ψ →D . The numerical cross sections are parametrized for future applications in hadronic matter. The particular temperature dependence of the J /ψ bound state leads to unusual behavior of the cross sections for endothermic J /ψ dissociation reactions. The quantum numbers of ψ and χ c cannot make their difference in mass in the temperature region 0.6T c T < T c but can make the ψ dissociation different from the χ c dissociation.

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