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

TL;DR

This paper compares microscopic UrQMD and hybrid hydrodynamic models to experimental hyperon data in Pb+Pb collisions at 40A and 158A GeV, exploring system size and centrality effects on hyperon production.

Contribution

It introduces a hybrid UrQMD+hydrodynamics model to study hyperon yields and spectra, bridging microscopic and macroscopic descriptions of heavy-ion collisions.

Findings

Hybrid model reproduces hyperon yields reasonably well.

System size influences hyperon production and spectra.

Model comparisons highlight the transition to full thermalization.

Abstract

We present results on the centrality and system size dependence of (multi-strange)hyperons in Pb+Pb collisions at 40$A$ and 158$A$ 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 ($\mid$y$\mid$ $\leq$ 0.5) and total multiplicities performed by the NA49 and NA57 Collaborations at 40$A$ and 158$A$ GeV. Furthermore, we compared our predictions to the centrality dependence of $\Lambda$, $\bar{\Lambda}$ and $\Xi^{-}$ rapidity spectra and total multiplicities at 40$A$ and 158$A$ GeV, where possible.