Rapidity distribution of protons from the potential version of UrQMD model and the traditional coalescence afterburner

Li, Qingfeng; Wang, Yongjia; Wang, Xiaobao; Shen, Chen

doi:10.1007/s11433-015-5768-2

“…As a matter of experience, the values for the parameter set (R 0 , P 0 ) might be chosen in the range of (3-4 fm, 0.25-0.35 GeV/c) in order to describe experimental data from HICs at SIS, AGS, and even SPS energies. Within such a large beam energy region, the relativistic effect on δr and δp between two baryons have been taken into account by the well-known Lorentz transformation (LT) from the computational two-nucleus center-of-mass system to the local rest frame of two particles [16,17], and it is found that it has visible effect on light fragments, although not on free nucleons, which should be paid attention.…”

Section: The Urqmd and The Coalescence Model Settingsmentioning

confidence: 99%

“…produced in nucleon-induced spallation reactions. Quite recently, the traditional coalescence afterburner has been combined with a potential version of UrQMD model to explain the production of free protons and 3 He clusters from HICs at the Brookhaven Alternating Gradient Synchroton (AGS) and the CERN Super Proton Synchrotron (SPS) energies [16,17] and it was found that, with only one parameter set of (R 0 ,P 0 )=(3.8 fm, 0.3 GeV/c) but using different stopping times for the former dynamic process, the rapidity distribution of both yields can be described reasonably well.…”

mentioning

confidence: 99%

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

Li

¹

,

Wang

²

,

Wang

³

et al. 2016

Sci. China Phys. Mech. Astron.

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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 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. PACS numbers: 24.10.Lx, 25.75.Dw, 25.75.-q, 24.10.-i a E-mail address: liqf@hutc.zj.cn 1 I. MOTIVIATIONThe production mechanism of particles and nuclei is a fundamental and essential problem for the whole evolution of the universe. With the help of macroscopic and/or microscopic transport models for heavy ion collisions (HICs) within a large range of beam energies from the GSI Schwerionen Synchrotron (SIS) up to the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC) energies, the process of a complete compression and decompression from initial two colliding nuclei can be described dynamically, with the possible occurrence of (phase) transitions from nuclear liquid to gas (LG) or from quark-gluon plasma (QGP) to hadron gas (HG). Such a model is, e.g. the Ultrarelativistic Quantum Molecular Dynamics (UrQMD)[1, 2] [? ] . After that, an afterburner is usually chosen for the freezeout of various particles (free baryons, mesons, etc.) or fragments (deuterons, tritons, Helium isotopes, etc.) which can then be used for comparison with corresponding experimental data. It is unavoidable that the afterburner should be paid much more attention when a serious comparison between calculations and experiments is needed for extracting, although, mainly the information of the compression phase at the early stage. Therefore, a large amount of such models are available but active in different beam energy regions (with their own problems when describing data). At low bombarding energies from several tens to several hundreds MeV/nucleon, the statistical multifragmentation model (SMM) [3, 4], the statistical evaporation model (HIVAP) [5, 6] and the statistical model (GEMINI) [7] are frequently used; at energies from several hundreds MeV/nucleon to several GeV/nucleon, the conventional phase-space coalescence model "Minimum Spanning Tree" (MST) [8] as well as the Simulated Annealing Clusterisation Algorithm (SACA)[12] are t...

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“…[39]. The experimental data of heavy-ion collisions in intermediate energies can be reproduced reasonably well by this model [39][40][41][42][43][44][45].…”

Section: Magnetic Field Calculations In Urqmdmentioning

confidence: 53%

Effect of internal magnetic field on collective flow in heavy ion collisions at intermediate energies

Sun

¹

,

Wang

²

,

Li

³

et al. 2019

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The properties of nuclear matter under extreme conditions of high temperature, density and isospin-asymmetry have attracted wide attentions in recent years. At present, heavy ion reactions in combination with corresponding model simulations are one of the most important ways to investigate this subject. It is known that a strong magnetic field can be created in heavy ion collisions. However, its effect on the motion of charged particles is usually neglected in previous transport model simulations. In this work, within the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, the temporal evolution and spatial distribution of the internal magnetic field are calculated. The magnetic field strength is found to reach about eB ≈ 470 MeV 2 (B ≈ 8 × 10 16 G) for Au+Au collisions at E lab =1 GeV/nucleon with impact parameter of 7 fm.The magnetic field in Cu+Au collisions exhibits somewhat different spatial distribution from that in Au+Au collisions. The magnetic field is found to affect the directed flow of pions at forward and backward rapidities to some extent, dependent of the impact parameter and beam energy while the effect on the elliptic flow is small. This suggests that, because π mesons produced in heavy ion collisions at intermediate energies are considered as a sensitive probe for the nuclear symmetry energy, it is necessary to consider the effect of the internal magnetic field. 25.75.Ld

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“…By this method, if the relative distances and momenta of two nucleons are smaller than and , respectively, they are considered to belong to the same fragment. With a proper set of and , the fragment mass distribution in HICs at intermediate energies is efficiently reproduced [45][46][47]. The parameters adopted in this study are The collective flow in HICs was studied extensively to deduce properties of formed hot and dense matter.…”

Section: Resultsmentioning

confidence: 99%

Nucleon effective mass splitting and density-dependent symmetry energy effects on elliptic flow in heavy ion collisions at E_lab= 0.09 ~ 1.5 GeV/nucleon *

Tong

¹

,

Li

²

,

Li

³

et al. 2020

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By incorporating an isospin-dependent form of the momentum-dependent potential in the ultra-relativistic quantum molecular dynamics (UrQMD) model, we systematically investigate effects of the neutron-proton effective mass splitting = and the density-dependent nuclear symmetry energy on the elliptic flow in + collisions at beam energies from 0.09 to 1.5 GeV/nucleon. It is found that at higher beam energies ( 0.25 GeV nucleon) with the approximately 75 MeV difference in slopes of the two different , and the variation of ranging from –0.03 to 0.03 at saturation density with isospin asymmetry , the has a stronger influence on the difference in between neutrons and protons, i.e., , than has. Meanwhile, at lower beam energies ( 0.25 GeV nucleon), is sensitive to both the and the . Moreover, the influence of on is more evident with the parameters of this study when using the soft, rather than stiff, symmetry energy.

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Rapidity distribution of protons from the potential version of UrQMD model and the traditional coalescence afterburner

Cited by 17 publications

References 41 publications

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

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

Effect of internal magnetic field on collective flow in heavy ion collisions at intermediate energies

Nucleon effective mass splitting and density-dependent symmetry energy effects on elliptic flow in heavy ion collisions at E_lab= 0.09 ~ 1.5 GeV/nucleon *

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Rapidity distribution of protons from the potential version of UrQMD model and the traditional coalescence afterburner

Cited by 17 publications

References 41 publications

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

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

Effect of internal magnetic field on collective flow in heavy ion collisions at intermediate energies

Nucleon effective mass splitting and density-dependent symmetry energy effects on elliptic flow in heavy ion collisions at Elab= 0.09 ~ 1.5 GeV/nucleon *

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Nucleon effective mass splitting and density-dependent symmetry energy effects on elliptic flow in heavy ion collisions at E_lab= 0.09 ~ 1.5 GeV/nucleon *