Understanding the energy dependence of in heavy ion collisions: interplay of volume and space-momentum correlations

Vincent Gaebel; Michel Bonne; Tom Reichert; Ajdin Burnic; Paula Hillmann; Marcus Bleicher

doi:10.1140/epja/s10050-020-00307-5

2023 Impact factor 2.6

Hadrons and Nuclei

Theory of Hot Matter and Relativistic Heavy-Ion Collisions (THOR)

Open Access

Eur. Phys. J. A (2021) 57: 55
https://doi.org/10.1140/epja/s10050-020-00307-5

Regular Article – Theoretical Physics

Understanding the energy dependence of $B_{2}$ in heavy ion collisions: interplay of volume and space-momentum correlations

Vincent Gaebel¹^a, Michel Bonne¹, Tom Reichert¹, Ajdin Burnic⁵, Paula Hillmann¹^,2^,3^,4 and Marcus Bleicher¹^,2^,3^,4

¹ Institut für Theoretische Physik, Goethe Universität Frankfurt, Max-von-Laue-Strasse 1, 60438, Frankfurt am Main, Germany
² GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstr. 1, 64291, Darmstadt, Germany
³ John von Neumann-Institut für Computing, Forschungzentrum Jülich, 52425, Jülich, Germany
⁴ Helmholtz Research Academy Hesse for FAIR, Campus Frankfurt, Frankfurt, Germany
⁵ University of Sarajevo, Sarajevo, Bosnia and Herzegovina

^a gaebel@itp.uni-frankfurt.de

Received: 23 June 2020
Accepted: 18 November 2020
Published online: 9 February 2021

Abstract

The deuteron coalescence parameter $B_{2}$ $$B_2$$ in proton+proton and nucleus+nucleus collisions in the energy range of $\sqrt{s_{NN}} =$ $\sqrt{s_{NN}}=$ 900–7000 GeV for proton + proton and $\sqrt{s_{NN}} =$ $\sqrt{s_{NN}}=$ 2–2760 GeV for nucleus + nucleus collisions is analyzed with the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) transport model, supplemented by an event-by-event phase space coalescence model for deuteron and anti-deuteron production. The results are compared to data by the E866, E877, PHENIX, STAR and ALICE experiments. The $B_{2}$ $$B_2$$ values are calculated from the final spectra of protons and deuterons. At lower energies, $\sqrt{s_{NN}} \leq 20$ $\sqrt{s_{NN}}\le 20$ GeV, $B_{2}$ $$B_2$$ drops drastically with increasing energy. The calculations confirm that this is due to the increasing freeze-out volume reflected in $B_{2} \sim 1 / V$ $B_2\sim 1/V$ . At higher energies, $\sqrt{s_{NN}} \geq 20$ $\sqrt{s_{NN}}\ge 20$ GeV, $B_{2}$ $$B_2$$ saturates at a constant level. This qualitative change and the vanishing of the volume suppression is shown to be due to the development of strong radial flow with increasing energy. The flow leads to strong space-momentum correlations which counteract the volume effect.

© The Author(s) 2020

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