Directed and elliptic flows of protons and deuterons in HADES Au+Au collisions at $\sqrt{s_{\rm NN}}=2.4$ GeV

TL;DR

This study uses a transport model with a microscopic coalescence approach to analyze proton and deuteron flows in Au+Au collisions at 2.4 GeV, highlighting the importance of momentum-dependent nuclear mean fields for matching experimental data.

Contribution

It demonstrates that incorporating isospin- and momentum-dependent nuclear mean fields accurately reproduces HADES experimental results, unlike momentum-independent models.

Findings

Momentum-dependent mean fields fit flow data well.

Momentum-independent models partially fit flow data.

Rapidity distributions are better matched with momentum-dependent mean fields.

Abstract

Within a transport model coupled with a microscopic coalescence model, the directed and elliptic flows of protons and deuterons as well as their scalling properties are studied in the centrality of 20-30% Au+Au collisions at $\sqrt{s_{\rm NN}}=2.4$ GeV. It is found that the flows as well as their scaling properties simulated with the isospin- and momentum-dependent nuclear mean field with an incompressibility $K_{0}=230$ MeV fit fairly the HADES data, while those simulated with the commonly used momentum-independent nuclear mean field with an incompressibility $K_{0}=380$ MeV can only fit partially the HADES data. Moreover, by checking the rapidity distributions of both protons and deuterons in the centrality of 0-10% Au+Au collisions at $\sqrt{s_{\rm NN}}=2.4$ GeV, we find that the rapidity distributions of deuterons are underestimated while those of protons are overestimated by the simulations with the momentum-independent nuclear mean field. In contrast, the rapidity distributions of both protons and deuterons simulated with the isospin- and momentum-dependent nuclear mean field are in good agreement with the HADES data. Our findings imply that the momentum dependence of nuclear mean field is an unavoidable feature for a fundamental understanding of nuclear matter properties and for the successful interpretation of the HADES data.