Helium-3 production from Pb+Pb collisions at SPS energies with the UrQMD model and the traditional coalescence afterburner

TL;DR

This study combines the UrQMD/M transport model with a coalescence afterburner to accurately predict helium-3 production in central Pb+Pb collisions at SPS energies, highlighting the importance of Lorentz transformations.

Contribution

It introduces a combined UrQMD/M and coalescence model approach, emphasizing the role of Lorentz transformations in helium-3 yield calculations at SPS energies.

Findings

UrQMD/M with t_cut=100±25 fm/c describes rapidity distributions well.

Lorentz transformation significantly affects helium-3 yield.

A specific coalescence parameter set reproduces experimental data.

Abstract

A potential version of the UrQMD (UrQMD/M) transport model and a traditional coalescence model are combined to calculate the production of $^3$He fragments in central Pb+Pb collisions at SPS energies 20-80 GeV/nucleon. It is found that the Lorentz transformation in the afterburner influences visibly the $^3$He yield and should be considered in calculations. The rapidity distribution of $^3$He multiplicities (including the concave shape) can be described well with UrQMD/M when it stops during t$_{\rm cut}$=100$\pm$25 fm$/c$ and the coalescence afterburner with one parameter set of ($R_0$,$P_0$)=(3.8 fm, 0.3 GeV$/$c) is taken into use afterwards.