Strangeness production in ultrarelativistic heavy-ion collisions. II. Evolution of flavor composition in scaling hydrodynamics

Abstract

Bjorken’s hydrodynamic description of the space-time evolution of the central rapidity region in ultrarelativistic heavy-ion collisions is extended to incorporate the chemical processes which affect the strangeness abundance. Scaling hydrodynamic equations which contain the rate equation for strangeness production and annihilation both in the plasma phase and in the hadron gas phase are integrated numerically assuming an almost adiabatic first-order phase transition from plasma to hadron gas. It is found that if a plasma is initially formed the resultant K/π ratio will be enhanced by about a factor of 3 from that in pp collisions. However, this ratio is still smaller than that in an equilibrium hadron gas and hence cannot be considered a direct signal of plasma formation.