(Anti-)strangeness production in heavy-ion collisions

TL;DR

This paper analyzes strange hadron production in heavy-ion collisions across a wide energy range using the PHSD model, highlighting successes at higher energies and discrepancies at lower energies, suggesting chiral symmetry restoration influences strangeness enhancement.

Contribution

It provides a detailed transport model analysis of strangeness production, emphasizing the role of hadronic dynamics and challenging the deconfinement transition explanation at FAIR/NICA energies.

Findings

PHSD reproduces experimental data above 8 GeV

Hadronic flavor-exchange reactions are crucial for final abundances

Strangeness production is underestimated below 8 GeV

Abstract

The production and dynamics of strange and antistrange hadrons in heavy-ion reactions from $\sqrt{s_{NN}} \approx$ 3 GeV to 200 GeV is analyzed within the Parton-Hadron-String-Dynamics (PHSD) transport model. The PHSD results for strange baryon and antibaryon production are roughly consistent with the experimental data starting from upper SPS energies. Nevertheless, hadronic final state flavor-exchange reactions are important for the actual abundances, in particular at large rapidities where hadronic dynamics, parton fragmentation and string decay dominate. A striking disagreement between the PHSD results and the available data persists, however, for bombarding energies below $\sqrt{s_{NN}} \approx$ 8 GeV where the strangeness production is significantly underestimated as in earlier HSD studies. This finding implies that the strangeness enhancement seen experimentally at FAIR/NICA energies cannot be attributed to a deconfinement phase transition or crossover but probably involves the approximate restoration of chiral symmetry in the hadronic phase.