Midrapidity cluster formation in heavy-ion collisions

TL;DR

This paper investigates cluster and hypernuclei formation at midrapidity in heavy-ion collisions using the PHQMD transport model, providing insights into their production mechanisms and survival in dense environments, and compares different clustering methods.

Contribution

It introduces a dynamic cluster formation model within PHQMD and compares MST and coalescence methods, demonstrating their consistent results across different transport approaches.

Findings

PHQMD successfully models cluster formation in heavy-ion collisions.

MST and coalescence methods yield similar deuteron observables.

The study offers an explanation for the 'ice in the fire' puzzle.

Abstract

We study the production of clusters and hypernuclei at midrapidity employing the Parton-Hadron-Quantum-Molecular-Dynamics (PHQMD) approach, a microscopic n-body transport model based on the QMD propagation of the baryonic degrees of freedom with density dependent 2-body potential interactions. In PHQMD the cluster formation occurs dynamically, caused by the interactions. The clusters are recognized by the Minimum Spanning Tree (MST) algorithm. We present the PHQMD results for cluster and hypernuclei formation in comparison with the available experimental data at relativistic energies. PHQMD allows to study the time evolution of formed clusters and the origin of their production, which helps to understand how such weakly bound objects are formed and survive in the rather dense and hot environment created in heavy-ion collisions. It offers therefore an explanation of the 'ice in the fire' puzzle. To investigate whether this explanation of the 'ice in the fire' puzzle applies only to the MST results we study also the deuterons production by coalescence. We embed MST and coalescence in the PHQMD and UrQMD transport approaches in order to obtain model independent results. We find that both clustering procedures give very similar results for the deuteron observables in the UrQMD as well as in the PHQMD environment. This confirms that our solution for the 'ice in the fire' puzzle is common to MST and coalescence and independent of the transport approach.