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

Tong, Luyao; Li, Pengcheng; Li, Fupeng; Wang, Yongjia; Li, Qingfeng; Liu, Fanxin

doi:10.1088/1674-1137/44/7/074103

Cited by 7 publications

(3 citation statements)

References 61 publications

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“…In Ref. [470], the neutron-proton effective mass splitting effect was studied by incorporating an isospin-dependent form of the momentum-dependent potential. In Ref.…”

Section: Mean-field Potentialmentioning

confidence: 99%

Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions

Wolter,

Colonna,

Cozma

et al. 2022

Preprint

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Transport models are the main method to obtain physics information on the nuclear equation of state and in-medium properties of particles from low to relativistic-energy heavy-ion collisions. The Transport Model Evaluation Project (TMEP) has been pursued to test the robustness of transport model predictions in reaching consistent conclusions from the same type of physical model. To this end, calculations under controlled conditions of physical input and set-up were performed with various participating codes. These included both calculations of nuclear matter in a box with periodic boundary conditions, which test separately selected ingredients of a transport code, and more realistic calculations of heavy-ion collisions. Over the years, five studies have been performed within this project. In this intermediate review, we summarize and discuss the present status of the project. We also provide condensed descriptions of the 26 participating codes, which contributed to some part of the project. These include the major codes in use today. After a compact description of the underlying transport approaches, we review the main results of the studies completed so far. They show, that in box calculations the differences between the codes can be well understood and a convergence of the results can be reached. These studies also highlight the systematic differences between the two families of transport codes, known under the names of Boltzmann-Uehling-Uhlenbeck (BUU) and Quantum Molecular Dynamics (QMD) type codes. However, when the codes were compared in full heavy-ion collisions using different physical models, as recently for pion production, they still yielded substantially different results. This calls for further comparisons of heavy-ion collisions with controlled models and of box comparisons of important ingredients, like momentum-dependent fields, which are currently underway. Our evaluation studies often indicate improved strategies in performing transport simulations and thus can provide guidance to code developers. Results of transport simulations of heavy-ion collisions from a given code will have more significance if the code can be validated against benchmark calculations such as the ones summarized in this review.

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“…In Ref. [470], the neutron-proton effective mass splitting effect was studied by incorporating an isospin-dependent form of the momentum-dependent potential. In Ref.…”

Section: Mean-field Potentialmentioning

confidence: 99%

Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions

Wolter,

Colonna,

Cozma

et al. 2022

Preprint

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“…Here, H is the total Hamiltonian function, it consists of the kinetic energy T and the effective interaction potential energy V. For studying HICs at intermediate energies, the following density and momentum dependent potential has been widely employed in QMD-like models [57][58][59][60][61][62],…”

Section: Urqmd Modelmentioning

confidence: 99%

Application of artificial intelligence in the determination of impact parameter in heavy-ion collisions at intermediate energies

Wang

Lü

et al. 2020

J. Phys. G: Nucl. Part. Phys.

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The impact parameter is one of the crucial physical quantities of heavy-ion collisions, and can affect obviously many observables at the final state, such as the multifragmentation and the collective flow. Usually, it cannot be measured directly in experiments but might be inferred from observables at the final state. Artificial intelligence has had great success in learning complex representations of data, which enables novel modeling and data processing approaches in physical sciences. In this article, we employ two of commonly used algorithms in the field of artificial intelligence, the convolutional neural networks (CNN) and light gradient boosting machine (LightGBM), to improve the accuracy of determining impact parameter by analyzing the proton spectra in transverse momentum and rapidity on the event-by-event basis. Au + Au collisions with the impact parameter of 0 ⩽ b ⩽ 10 fm at intermediate energies (E lab = 0.2–1.0 GeV/nucleon) are simulated with the ultrarelativistic quantum molecular dynamics model to generate the proton spectra data. It is found that the average difference between the true impact parameter and the estimated one can be smaller than 0.1 fm. The LightGBM algorithm shows an improved performance with respect to the CNN on the task in this work. By using the LightGBM’s visualization algorithm, one can obtain the important feature map of the distribution of transverse momentum and rapidity, which may be helpful in inferring the impact parameter or centrality in heavy-ion experiments.

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“…Quite a few observables have been found or predicted to be sensitive to the nuclear symmetry energy as, e.g., neutron and proton yields and flow ratios, double ratios, or differences, 3 H/ 3 He yield ratio, π − /π + and K 0 /K + meson production ratios, the Σ − /Σ + ratio [24][25][26][27][28][29][30][31][32][33][34][35][36]. In spite of the progress made, a tight constraint on the density-dependent nuclear symmetry energy E sym (ρ) by using HIC observables is still very difficult to achieve [37][38][39][40][41]. Extracting E sym (ρ) with HIC should rely on both transport model simulations and experimental measurements, while various transport models have different philosophies/assumptions/parameters, and as a result constraints on E sym (ρ) with different transport models are usually different to some extent.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the Effect of Initial Fluctuations on Isospin-Sensitive Observables from Heavy-Ion Collisions at Intermediate Energies

Wang

Gao

2021

Symmetry

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Initial fluctuation is one of the ingredients that washes fingerprints of the nuclear symmetry energy on observables in heavy-ion collisions. By artificially using the same initial nuclei in all collision events, the effect of the initial fluctuation on isospin-sensitive observables, e.g., the yield ratio of free neutrons with respect to protons Nn/Np, 3H/3He yield ratio, the yield ratio between charged pions π−/π+, and the elliptic flow ratio or difference between free neutrons and protons v2n/v2p (v2n-v2p), are studied within the ultrarelativistic quantum molecular dynamics (UrQMD) model. In practice, Au + Au collisions with impact parameter b = 5 fm and beam energy Elab = 400 MeV/nucleon are calculated. It is found that the effect of the initialization on the yields of free protons and neutrons is small, while for the yield of pions, the directed and elliptic flows are found to be apparently influenced by the choice of initialization because of the strong memory effects. Regarding the isospin-sensitive observables, the effect of the initialization on Nn/Np and 3H/3He is negligible, while π−/π+ and v2n/v2p (v2n-v2p) display a distinct difference among different initializations. The fingerprints of symmetry energy on π−/π+ and v2n/v2p can be either enhanced or reduced when different initializations are utilized.

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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 *

Cited by 7 publications

References 61 publications

Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions

Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions

Application of artificial intelligence in the determination of impact parameter in heavy-ion collisions at intermediate energies

Quantifying the Effect of Initial Fluctuations on Isospin-Sensitive Observables from Heavy-Ion Collisions at Intermediate Energies

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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 *

Cited by 7 publications

References 61 publications

Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions

Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions

Application of artificial intelligence in the determination of impact parameter in heavy-ion collisions at intermediate energies

Quantifying the Effect of Initial Fluctuations on Isospin-Sensitive Observables from Heavy-Ion Collisions at Intermediate Energies

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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 *