Strangeness production in ultrarelativistic heavy-ion collisions. I. Chemical kinetics in the quark-gluon plasma

We develop a kinetic theory of chemical reactions in a quark-gluon plasma in order to study the evolution of flavor composition in ultrarelativistic nucleus-nucleus collisions. The rates of production and annihilation of strange-quark pairs are computed in lowest order in perturbation theory assuming local equilibrium with respect to other, more frequent collision processes. Quantum-statistical effects are taken into account. The hydrodynamic equations coupled to the rate equation are derived and solved numerically in a homogeneous plasma, simulating the approach toward complete chemical equilibrium. The corresponding relaxation times are computed.