System and Energy Dependence of Strangeness Production with STAR

Abstract

The yields and spectra of strange hadrons have each been measured by STAR as a function of centrality in $\rm \sqrt{s_{NN}}=$ 200 GeV AuAu collisions. By comparison to measurements in pp and dAu at $\rm \sqrt{s_{NN}}=200$ GeV and in AuAu at $\rm \sqrt{s_{NN}}=62$ GeV the dependence on system size and energy is studied. Short-lived resonances, such as $\Sigma (1385)$ and $\Lambda (1520)$, that may decay and regenerate in the medium, are used to examine the dynamical evolution between production and freeze-out for these systems. Particle production is investigated by comparison to thermal models, which assume a simple scaling of the yield with $\rm N_{part}$, in order to calculate the strangeness enhancement. Our hyperon measurements in AuAu indicate that $\rm N_{bin}$ may be a more appropriate scale for the strangeness correlation volume. In this case canonical suppression can not be simply parameterized with the geometrical overlap volume but will depend on the individual quark content of each particle. This theory is tested by comparing the data from different collision systems and centralities.