Deep sub-threshold $\Xi$ and $\Lambda$ production in nuclear collisions with the UrQMD transport model

TL;DR

This paper uses the UrQMD transport model to analyze deep sub-threshold hyperon production in nuclear collisions, highlighting the dominant role of hyperon strangeness exchange and discussing discrepancies with experimental data.

Contribution

It introduces strangeness exchange reactions into UrQMD to better simulate hyperon production at sub-threshold energies, providing insights into the mechanisms involved.

Findings

Hyperon strangeness exchange dominates $ ext{Xi}^-$ production.

The model reproduces single strange hadron yields in Ar+KCl collisions.

Discrepancies remain between simulated and experimental $ ext{Xi}^-/ ext{Lambda}$ ratios.

Abstract

We present results on deep sub threshold hyperon production in nuclear collisions, with the UrQMD transport model. Introducing anti-kaon+baryon and hyperon+hyperon strangeness exchange reactions we obtain a good description of experimental data on single strange hadron production in Ar+KCl reactions at $E_{lab}=1.76$ A GeV. We find that the hyperon strangeness exchange is the dominant process contributing to the $\Xi^-$ yield, however remains short of explaining the $\Xi^-/\Lambda$ ratio measured with the HADES experiment. We also discuss possible reasons for the discrepancy with previous studies and the experimental results, finding that many details of the transport simulation may have significant effects on the final $\Xi^-$ yield.