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12 pages, 1260 KiB

Open AccessArticle

Probing the Neutron Skin of Unstable Nuclei with Heavy-Ion Collisions

by Junping Yang, Xiang Chen, Ying Cui, Zhuxia Li and Yingxun Zhang

Universe 2023, 9(5), 206; https://doi.org/10.3390/universe9050206 - 25 Apr 2023

Viewed by 1134

Abstract

To improve the constraints of symmetry energy at subsaturation density, measuring and accumulating more neutron skin data for neutron-rich unstable nuclei is naturally required. Aiming to probe the neutron skin of unstable nuclei by using low-intermediate-energy heavy-ion collisions, we develop a new version [...] Read more.

To improve the constraints of symmetry energy at subsaturation density, measuring and accumulating more neutron skin data for neutron-rich unstable nuclei is naturally required. Aiming to probe the neutron skin of unstable nuclei by using low-intermediate-energy heavy-ion collisions, we develop a new version of an improved quantum molecular dynamics model, in which the neutron skin of the initial nucleus and the mean-field potential in nucleon propagation are consistently treated. Our calculations show that the three observables, such as the cross-sections of the primary projectile-like residues with

A > 100

(

σ_{A > 100}

), the difference of

σ_{A > 100}

between

^{132}

Sn +

^{124}

Sn and

^{124}

Sn +

^{124}

Sn systems (

δ σ_{A > 100}

), and the neutron-to-proton yield ratio (

R (n / p)

) in the transverse direction, could be used to measure the neutron skin of the unstable nuclei and to constrain the slope of the symmetry energy in the future. Full article

(This article belongs to the Special Issue Intermediate-Energy Heavy-Ion Collisions and Studies with Transport Models)

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14 pages, 763 KiB

Open AccessArticle

Pauli Exclusion Classical Potential for Intermediate-Energy Heavy-Ion Collisions

by Claudio O. Dorso, Guillermo Frank and Jorge A. López

Universe 2023, 9(3), 119; https://doi.org/10.3390/universe9030119 - 25 Feb 2023

Viewed by 741

Abstract

This article presents a classical potential used to describe nucleon–nucleon interactions at intermediate energies. The potential depends on the relative momentum of the colliding nucleons and can be used to describe interactions at low momentum transfer mimicking the Pauli exclusion principle. We use [...] Read more.

This article presents a classical potential used to describe nucleon–nucleon interactions at intermediate energies. The potential depends on the relative momentum of the colliding nucleons and can be used to describe interactions at low momentum transfer mimicking the Pauli exclusion principle. We use the potential with molecular dynamics to study finite nuclei, their binding energy, radii, symmetry energy, and a case study of collisions. Full article

(This article belongs to the Special Issue Intermediate-Energy Heavy-Ion Collisions and Studies with Transport Models)

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9 pages, 339 KiB

Open AccessCommunication

Beam Energy Dependence of the Linear and Mode-Coupled Flow Harmonics Using the a Multi-Phase Transport Model

by Niseem Magdy

Universe 2023, 9(2), 107; https://doi.org/10.3390/universe9020107 - 18 Feb 2023

Cited by 2 | Viewed by 708

Abstract

In the framework of the A Multi-Phase Transport (AMPT) model, the multi-particle azimuthal cumulant method is used to calculate the linear and mode-coupled contributions to the quadrangular flow harmonic (

v_{4}

) and the mode-coupled response coefficient as functions of centrality in [...] Read more.

In the framework of the A Multi-Phase Transport (AMPT) model, the multi-particle azimuthal cumulant method is used to calculate the linear and mode-coupled contributions to the quadrangular flow harmonic (

v_{4}

) and the mode-coupled response coefficient as functions of centrality in Au+Au collisions at

\sqrt{s_{N N}}

= 200, 39, 27 and 19.6 GeV. This study indicates that the linear and mode-coupled contributions to

v_{4}

are sensitive to beam energy change. Nevertheless, the correlations between different-order flow symmetry planes and the mode-coupled response coefficients show weak beam energy dependence. In addition, the presented results suggest that the experimental measurements that span a broad range of beam energies can be an additional constraint for the theoretical model calculations. Full article

(This article belongs to the Special Issue Intermediate-Energy Heavy-Ion Collisions and Studies with Transport Models)

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14 pages, 494 KiB

Open AccessArticle

Revisiting Angular Momentum Conservation in Transport Simulations of Intermediate-Energy Heavy-Ion Collisions

by Rong-Jun Liu and Jun Xu

Universe 2023, 9(1), 36; https://doi.org/10.3390/universe9010036 - 3 Jan 2023

Cited by 3 | Viewed by 986

Abstract

Based on the well-calibrated IBUU transport model, we have studied the dynamical effect of incorporating rigorous angular momentum conservation in each collision of particles with homework setups. The constraint of the rigorous angular momentum conservation requires in-plane collisions and side jumps of particles [...] Read more.

Based on the well-calibrated IBUU transport model, we have studied the dynamical effect of incorporating rigorous angular momentum conservation in each collision of particles with homework setups. The constraint of the rigorous angular momentum conservation requires in-plane collisions and side jumps of particles after their collision. Since the option is not unique, we have compared two typical prescriptions with the original one. While the results depend quantitatively on the choice of the prescription, we found that the angular momentum conservation generally reduces local density fluctuations and thus the collision rate and may have some influence on the density evolution, the collective flow, and even the pion production in transport simulations of intermediate-energy heavy-ion collisions. Full article

(This article belongs to the Special Issue Intermediate-Energy Heavy-Ion Collisions and Studies with Transport Models)

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13 pages, 1294 KiB

Open AccessArticle

Pion Productions with Isospin-Dependent In-Medium Cross Sections

by Myungkuk Kim, Youngman Kim, Sangyong Jeon and Chang-Hwan Lee

Universe 2022, 8(11), 564; https://doi.org/10.3390/universe8110564 - 27 Oct 2022

Viewed by 1027

Abstract

Total pion yields and

π^{-} / π^{+}

ratios in two Sn+Sn collision systems,

^{132}

Sn+

^{124}

Sn (neutron rich) and

^{108}

Sn+

^{112}

Sn (neutron poor) at

E = 270 A

MeV, are significant observables in SAMURAI Pion-Reconstruction and Ion-Tracker (S [...] Read more.

Total pion yields and

π^{-} / π^{+}

ratios in two Sn+Sn collision systems,

^{132}

Sn+

^{124}

Sn (neutron rich) and

^{108}

Sn+

^{112}

Sn (neutron poor) at

E = 270 A

MeV, are significant observables in SAMURAI Pion-Reconstruction and Ion-Tracker (S

π

RIT) experiments. Based on a recently developed transport model, DaeJeon Boltzmann–Uehling–Uhlenbeck (DJBUU), we investigate the isospin-dependent inmedium effects by including density- and isospin-dependent cross sections for

Δ

baryon productions. We compare our results with the S

π

RIT data by considering these effects. We find that the yields as well as the ratios strongly depend on the in-medium effect, especially isospin-dependent in-medium cross sections for

Δ

resonances. Full article

(This article belongs to the Special Issue Intermediate-Energy Heavy-Ion Collisions and Studies with Transport Models)

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10 pages, 712 KiB

Open AccessArticle

Nuclear Bubble Configuration in Heavy-Ion Collisions

by Kyungil Kim, Sangyong Jeon, Chang-Hwan Lee and Youngman Kim

Universe 2022, 8(10), 499; https://doi.org/10.3390/universe8100499 - 22 Sep 2022

Viewed by 1157

Abstract

We study the effects of a bubble configuration in a nucleus on heavy-ion collisions at a few tens and hundreds A MeV. We first investigate the bubble structure of

^{206}

Hg using the relativistic continuum Hartree–Bogoliubov theory and then study the

^{206}

Hg [...] Read more.

We study the effects of a bubble configuration in a nucleus on heavy-ion collisions at a few tens and hundreds A MeV. We first investigate the bubble structure of

^{206}

Hg using the relativistic continuum Hartree–Bogoliubov theory and then study the

^{206}

Hg +

^{208}

Pb and

^{206}

Hg+

^{206}

Hg reactions using the DaeJeon–Boltzmann–Uehling–Uhlenbeck (DJBUU) transport model. To see the role of the bubble structure, we consider the maximum density of the produced nuclear matter, directed flow of neutrons and protons, and

π^{-} / π^{+}

ratio. We observe that the maximum density is smaller with a bubble nucleus, and the directed flow of nucleons and

π^{-} / π^{+}

ratio may depend on the bubble structure. Full article

(This article belongs to the Special Issue Intermediate-Energy Heavy-Ion Collisions and Studies with Transport Models)

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9 pages, 569 KiB

Open AccessArticle

Effects of Initial Density Fluctuations on Cumulants in Au + Au Collisions at

\sqrt{s_{N N}}

= 7.7 GeV

by Xiaoqing Yue, Yongjia Wang, Qingfeng Li and Fuhu Liu

Universe 2022, 8(9), 491; https://doi.org/10.3390/universe8090491 - 18 Sep 2022

Cited by 1 | Viewed by 1220

Abstract

Within the ultrarelativistic quantum molecular dynamics (UrQMD) model, the effect of initial density fluctuations on cumulants of the net-proton multiplicity distribution in Au + Au Collisions at

\sqrt{s_{N N}}

= 7.7 GeV was investigated by varying the minimum distance

d_{\min}

between [...] Read more.

Within the ultrarelativistic quantum molecular dynamics (UrQMD) model, the effect of initial density fluctuations on cumulants of the net-proton multiplicity distribution in Au + Au Collisions at

\sqrt{s_{N N}}

= 7.7 GeV was investigated by varying the minimum distance

d_{\min}

between two nucleons in the initialization. It was found that the initial density fluctuations increased with the decrease of

d_{\min}

from 1.6 fm to 1.0 fm, and the influence of

d_{\min}

on the magnitude of the net-proton number fluctuation in a narrow pseudorapidity window (

Δ η \leq

4) was negligible even if it indeed affected the density evolution during the collision. At a broad pseudorapidity window (

Δ η \geq

4), the cumulant ratios were enlarged when the initial density fluctuations were increased with the smaller value of

d_{\min}

, and this enhancement was comparable to that observed in the presence of the nuclear mean-field potential. Moreover, the enhanced cumulants were more evident in collisions with a larger impact parameter. The present work demonstrates that the fingerprint of the initial density fluctuations on the cumulants in a broad pseudorapidity window is clearly visible, while it is not obvious as the pseudorapidity window becomes narrow. Full article

(This article belongs to the Special Issue Intermediate-Energy Heavy-Ion Collisions and Studies with Transport Models)

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Review

Jump to: Research

17 pages, 5066 KiB

Open AccessReview

Improved Quantum Molecular Dynamics Model and Its Application to Ternary Breakup Reactions

by Junlong Tian, Xian Li and Cheng Li

Universe 2022, 8(11), 555; https://doi.org/10.3390/universe8110555 - 25 Oct 2022

Viewed by 920

Abstract

Collisions of very heavy nuclei ¹⁹⁷Au+¹⁹⁷Au at the energy range of 5–30 A MeV have been studied within the improved quantum molecular dynamics (ImQMD) model. A class of ternary events satisfying a nearly complete balance of mass numbers is selected [...] Read more.

Collisions of very heavy nuclei ¹⁹⁷Au+¹⁹⁷Au at the energy range of 5–30 A MeV have been studied within the improved quantum molecular dynamics (ImQMD) model. A class of ternary events satisfying a nearly complete balance of mass numbers is selected and we find that the probability of ternary breakup depends on the incident energy and the impact parameter. It is also found that the largest probability of ternary breakup is located at the energy around 24 A MeV for the system ¹⁹⁷Au+¹⁹⁷Au. The experimental mass distributions and angular distributions for the system ¹⁹⁷Au+¹⁹⁷Au ternary breakup fragments can be reproduced well by the calculation with the ImQMD model at the energy of 15 A MeV. The modes and mechanisms of ternary and quaternary breakup are studied by time-dependent snapshots of ternary events. The direct prolate, direct oblate, and cascade ternary breakup modes, are manifested and their production probabilities are obtained. The characteristic features in ternary breakup events, three mass-comparable fragments, and the very fast, nearly collinear breakup, account for the two-preformed-neck shape of the composite system. The mean free path of nucleons in the reaction system is studied and the shorter mean free path is responsible for the ternary breakup with three mass comparable fragments, in which the two-body dissipation mechanism plays a dominant role. Full article

(This article belongs to the Special Issue Intermediate-Energy Heavy-Ion Collisions and Studies with Transport Models)

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