2-STAGE EQUILIBRATION IN HIGH-ENERGY HEAVY-ION COLLISIONS

Using the (lowest-order) perturbative QCD, we argue that high energy heavy ion collisions proceed via two stages: equilibration of gluons takes time tau(g) approximately 1/2 fm/c, while production and equilibration of quarks needs time at least tau(q) approximately 2 fm/c. If so, the initial gluon plasma is much hotter than usually estimated, T(g) approximately 400 MeV, which leads to enhanced charm production and significant modifications of other proposed signals.