Influence of coalescence parameters on the production of protons and Helium-3 fragments

TL;DR

This study investigates how coalescence parameters affect proton and Helium-3 fragment production in heavy-ion collisions using the UrQMD model, revealing time-dependent correlations and parameter sensitivities that influence yield and flow results.

Contribution

It introduces a detailed analysis of coalescence parameter effects on light fragment production, emphasizing the importance of time evolution and parameter choices in transport model simulations.

Findings

Protons are best described with parameters at 30-60 fm/c.

Helium-3 requires longer evolution times of 60-90 fm/c.

Consistent proton results are obtained at mid-rapidity, but Helium-3 results are less consistent.

Abstract

The time evolution of protons and $^3$He fragments from Au+Au/Pb+Pb reactions at 0.25, 2, and 20 GeV$/$nucleon is investigated with the potential version of the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) model combined with the traditional coalescence afterburner. In the coalescence process, the relative distance $R_0$ and relative momentum $P_0$ are surveyed in the range of 3-4 fm and 0.25-0.35 GeV$/$c, respectively. For both clusters, a strong reversed correlation between $R_0$ and $P_0$ is seen and it is time-dependent as well. For protons, the accepted ($R_0$, $P_0$) bands lie in the time interval 30-60 fm$/$c, while for $^3$He, a longer time evolution (at about 60-90 fm$/$c) is needed. Otherwise, much smaller $R_0$ and $P_0$ values should be chosen. If we further look at the rapidity distributions from both central and semi-central collisions, it is found that the accepted [$t_{\rm cut}, (R_0, P_0$)] assemble can provide consistent results for proton yield and collective flows especially at mid-rapdities, while for $^3$He, the consistency is destroyed at both middle and projectile-target rapidities.