arXiv subjects

De-Qing Fang

Publications and source records attributed to De-Qing Fang.

9 recordsLinked to original sources

arXiv2026

Neutron Skin Effects on Particle Emission in Heavy-Ion Collisions: A Topic Review with Astrophysical and Nuclear Structure Connections

The neutron skin, defined by the difference between neutron and proton root-mean-square radii, is a characteristic manifestation of isospin asymmetry and an important probe of the isovector nuclear interaction. This focused review examines how neutron skins influence particle emission and collective dynamics in heavy-ion collisions, from the Fermi-energy regime to ultra-relativistic energies. By modifying the initial neutron and proton density profiles, the neutron skin affects the isospin composition and geometry of the participant region, pre-equilibrium emission, particle production, fragment formation, and collective flow. We review neutron-to-proton and $\rm{t}/^3\rm{He}$ yield ratios, light clusters, pion ratios, bremsstrahlung photons, isoscaling and fragment momentum distributions, and neutron-proton differential flow and momentum observables, emphasizing their interplay with the symmetry energy and transport dynamics. At high energies, neutron skins also modify the initial geometry, eccentricities, multiplicities, and anisotropic flows in isobar and heavy-nucleus collisions. We discuss the challenge of disentangling these effects from deformation, surface diffuseness, shell structure, clustering, and model dependence. Broader connections to parity-violating electron scattering, dipole responses, coherent elastic neutrino-nucleus scattering, SRC-induced proton skins in momentum space, and neutron-star observables are also explored. Finally, we highlight opportunities from radioactive beams, improved collision experiments, microscopic many-body and transport calculations, and Bayesian inference. Combining multiple reaction systems and observables with complementary nuclear-structure and astrophysical information will be essential for quantitatively constraining neutron skins and the density dependence of the symmetry energy.

nucl-th↗

arXiv2026

Understanding Energy Dependent Hadronic Calorimeter Response from a Machine Learning Perspective

To meet the precision requirements of future high-energy physics experiments, improving the energy resolution of hadronic calorimeters remains a critical challenge. This work presents a systematic investigation of hadronic energy reconstruction using machine learning, highlighting the roles of various signal channels, including scintillation light, Cherenkov light, charged particles, and the full three-dimensional topology of hadronic showers in the energy range up to 10 GeV. Throughout this study, detector effects are not taken into account. Under these conditions, the intrinsic resolution of hadronic showers reaches approximately $(10.8\pm0.3)\% / \sqrt{E/GeV}$ when all signal channels and the full 3D shower information are fully utilized. Compared with the traditional signal-summing approach, machine-learning-based reconstruction can significantly improve energy resolution, even under a limited sampling fraction of 10\%, enhancing it from $(57.6\pm3.7)\%/\sqrt{E/GeV}$ to $(34.1\pm2.8)\%/\sqrt{E/GeV}$. These results highlight the critical importance of both multi-channel information and detailed spatial shower features in hadronic energy reconstruction, and demonstrate the substantial potential of combining high-granularity and dual-readout calorimeter designs with machine-learning-based reconstruction techniques for future experiments.

hep-ex↗

arXiv2024

Neutron skin and its effects in heavy-ion collisions

Neutron skin is an exotic phenomena in unstable nuclei. The various effects in nuclear reactions caused by the neutron skin and also its relation with the properties of nuclear structure are reviewed in this article. Based on numerous studies with theoretical models, strong correlations have been found between the neutron skin thickness and neutron removal cross section, neutron/proton yield ratio, t/\ch{^3He} yield ratio, neutron-proton momentum difference, isoscaling parameter, photon production, reaction cross sections for neutron induced reactions, charge-changing cross sections difference of mirror nuclei, astrophysical $S$-factor, and other quantities in nuclear reactions induced by neutron-rich nuclei. Moreover, the relationships between neutron skin thickness and some properties of nuclear structure, such as $α$-cluster formation, $α$ decay, nuclear surface, nuclear temperature, and proton radii difference of mirror nuclei, have also been investigated. It also has been shown that the neutron skin plays a crucial role in relativistic heavy-ion collisions. Experimentally, an unstable nucleus with neutron skin can be generated by radioactive nuclear beam facilities, and the thickness of neutron skin could be extracted by measuring the sensitive probes, which further helps giving stringent constraints on the equation of state of asymmetric nuclear matter and properties of neutron stars.

nucl-th↗

arXiv2024

Fudan Multi-purpose Active TArget Time Projection Chamber (fMeta-TPC) for Photonnuclear Reaction Experiments

Active Target Time Projection Chambers (AT-TPCs) are state-of-the-art tools in the field of low-energy nuclear physics, particularly suitable for experiments using low-intensity radioactive ion beams or gamma rays. The Fudan Multi-purpose Active Target Time Projection Chamber (fMeta-TPC) with 2048 channels has been developed to study $α$-clustering nuclei. {\fcb In this work, the focus is on the study of the photonuclear reaction with the Laser Compton Scattering (LCS) gamma source, especially for the decay of the highly excited $α$-cluster state.} The design of fMeta-TPC is described and a comprehensive evaluation of its offline performance is performed by ultraviolet (UV) laser and $^{241}$Am $α$ source. The result shows that the intrinsic angular resolution of the detector is within 0.30$^{\circ}$ and has an energy resolution of 6.85\% for 3.0 MeV $α$ particles. The gain uniformity of the detector is about 10\% (RMS/Mean), tested by the $^{55}$Fe X-ray source.

physics.ins-det↗

arXiv2024

Isovector giant dipole resonance mode with an improved propagation approach in the framework of EQMD model

The Extended Quantum Molecular Dynamics (EQMD) model is one of the few QMD-like transport approaches that can describe the $α$-clustering structure with efficient computational power. However, compared to most QMD-like models, the choice of equation of state (EOS) for nuclear matter is very limited. In this work, a Monte Carlo integral method is employed to calculate the density integration with non-integer exponent. We demonstrate the superiority of our approach by studying the isovector giant dipole resonance (IVGDR). This improvement will be beneficial for the EQMD model to study more valuable effects for heavy ion collisions in the near future.

nucl-th↗

arXiv2024

Shear viscosity of nucleonic matter

The research status of the shear viscosity of nucleonic matter is reviewed. Some methods to calculate the shear viscosity of nucleonic matter are introduced, including mean free path, Green-Kubo, shear strain rate, Chapman-Enskog and relaxation time approximation. Based on these methods, results for infinite and finite nucleonic matter are discussed, which are attempts to investigate the universality of the ratio of shear viscosity over entropy density and transport characteristics like the liquid-gas phase transition in nucleonic matter. In addition, shear viscosity is also briefly discussed for the quantum chrodynamical matter produced in relativistic heavy-ion collisions.

nucl-th↗

arXiv2023

Temperature and density effects on the two-nucleon momentum correlation function from excited single nuclei

Two-nucleon momentum correlation functions are investigated for different single thermal sources at given initial temperature $(T)$ and density $(ρ)$. To this end, the space-time evolutions of various single excited nuclei at $T$ $= 1 - 20$ $MeV$ and $ρ$ = 0.2 - 1.2 $ρ_0$ are simulated by using the thermal isospin-dependent quantum molecular dynamics $(ThIQMD)$ model. Momentum correlation functions of identical proton-pairs ($C_{pp}(q)$) or neutron-pairs ($C_{nn}(q)$) at small relative momenta are calculated by $Lednick\acute{y}$ and $Lyuboshitz$ analytical method. The results illustrate that $C_{pp}(q)$ and $C_{nn}(q)$ are sensitive to the source size ($A$) at lower $T$ or higher $ρ$, but almost not at higher $T$ or lower $ρ$. And the sensitivities become stronger for smaller source. Moreover, the $T$, $ρ$ and $A$ dependencies of the Gaussian source radii are also extracted by fitting the two-proton momentum correlation functions, and the results are consistent with the above conclusions.

nucl-th↗

arXiv2015

Nuclear medium effect on nuclear modification factor of protons and pions in intermediate-energy heavy ion collisions

Nuclear modification factor ($R_{cp}$) of protons and pions are investigated by simulating Au + Au collisions from 0.8 to 1.8$A$ GeV in a framework of an isospin-dependent quantum molecular dynamics (IQMD) model. $R_{cp}$ of protons rises with the increase of \pt~ at different beam energies owing to radial flow and Cronin effect. The rate of increase of \rcp~ is suppressed at higher beam energies. The significant difference of $R_{cp}$ between protons and pions indicates different medium effects between protons and pions. By changing the in-medium nucleon-nucleon cross section, the $R_{cp}$ of protons changes a lot, while the $R_{cp}$ of pions does not. Taking the pion absorption into account, the $R_{cp}$ of pions becomes close to unity without $p_{T}$ dependence after deactivating the reaction $πN \rightarrow Δ$, while there is nearly no change on proton. This suggests that the pion absorption plays a dominant role on pion dynamics and have slight effect for proton dynamics.

nucl-th↗

arXiv1999

Isospin Effects of the Critical Behavior in the Lattice Gas Model

Isospin effects of the critical phenomena were studied via Xe isotopes in the frame of lattice gas model. All the critical temperatures for four Xe isotopes are close to 5.5 MeV at the same freeze-out density of about 0.39 $ρ_0$. The critical values of power law parameter of mass distribution, mean multiplicity of intermediate mass fragments (IMF), information entropy and Campi's second moment show minor dependence on the isospin at the critical point.

nucl-th↗