Strangeness dynamics in heavy-ion collisions: the K/pi ratios and the   lifetime of a fireball
  We propose a non-equilibrium, hadronic kinetic model for describing the relative abundance of strange particles in ultra-relativistic heavy-ion collisions. The energy dependence of the multiplicity ratios of charged kaons and lambdas to pions are studied in detail. The pronounced peak in positively charged K/pi is conjectured to be due to the decreasing lifetime of a fireball with an increase in beam energy above 30 AGeV. Such a behaviour may be the consequence of a stronger stopping at lower beam energies. We study the dependence of the multiplicity ratios on energy and baryon density of the fireball and its total lifetime. 
Boris Tomasik and Evgeni E Kolomeitsev