Thermalization of quarks and gluons in heavy-ion collisions.

Abstract

The thermalization problem in relativistic heavy-ion collisions is considered. The initial momentum distribution of the quarks and gluons in a nucleus-nucleus collision before thermalization takes place is first determined. It is then argued that the relativistic Fokker-Planck equation is the appropriate transport equation to describe the time evolution of the quark-gluon system. In terms of a scaled time variable, the thermalization time is determined without fully solving the Fokker-Planck equation. The actual proper time of local thermalization is then estimated on the basis of some reasonable inputs on the soft interactions among quarks and gluons; the resultant value is of order 0.1 fm/c. The time for global (in rapidity) thermalization is longer.