Centrality and system size dependence of (multi-strange) hyperons at 40A and 158A GeV: A comparison between a binary collision and a Boltzmann + hydrodynamic hybrid model

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We present results on the centrality and system size dependence of (multi-strange)hyperons in Pb+Pb collisions at 40A and 158A GeV from the Ultra-relativistic Quantum Molecular Dynamics (UrQMD-v2.3) model and a coupled Boltzmann+hydrodynamics calculation. The second approach is realized in a hybrid fashion based on UrQMD with an intermediate hydrodynamical evolution for the hot and dense stage of the collision. This implementation allows a comparison of microscopic transport calculations with hydrodynamic simulations to explore the transition from a system that is not fully equilibrated such as C+C or Si+Si collisions, to a supposedly fully equilibrated system, such as that created in Pb+Pb reactions. The results of our calculation are compared to measurements of the (anti-)hyperon yields at midrapidity (≤ 0.5) and total multiplicities performed by the NA49 and NA57 Collaborations at 40A and 158A GeV. Furthermore, we compared our predictions to the centrality dependence of Λ, Λ and Ξ⁻ rapidity spectra and total multiplicities at 40A and 158A GeV, where possible.