arXiv subjects

Chun-Wang Ma

Publications and source records attributed to Chun-Wang Ma.

At least 19 recordsLinked to original sources

arXiv2026

Signals for Nuclear Solid-Liquid Phase Transition in Clustering Nuclei

The nuclear phase diagram remains a fundamental challenge, where uncovering how the cluster degree of freedom evolves with temperature and energy is essential to understand the intriguing crossover between cluster, nucleon, and nuclear astrophysics. A new first-order phase transition, the nuclear solid-liquid phase transition (SLPT), emerges spontaneously from nucleonic degrees of freedom in low-energy heavy-ion collisions. Clear signals of the SLPT are identified as a region of negative heat capacity in smaller systems (e.g., $^{12}\text{C} + ^{12}\text{C}$ and $^{16}\text{O} + ^{12}\text{C}$) and a caloric plateau in larger systems (e.g., $^{28}\text{Si} + ^{12}\text{C}$ and $^{40}\text{Ca} + ^{12}\text{C}$), along with prominent behaviors in the number of fragment species and information entropy. Moreover, the pairwise distance probability density function provides a direct spatial fingerprint of the melting, where long-range crystalline $\alpha$-cluster peaks vanish above the transition temperature, giving way to a liquid-like distribution. This new phase transition unifies the many-body dynamics of finite constituents, extending from nanoscale clusters to nuclear systems. Beyond advancing nuclear structure and phase diagrams, these insights offer profound implications for astrophysics, notably linking structural evolution to astrophysical phase transitions via nuclear cluster dissolution in supernovae.

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arXiv2026

Effects of light-cluster degrees of freedom on collective flows in heavy-ion collisions at FOPI energies

Within a lattice Boltzmann-Uehling-Uhlenbeck transport model coupled to a kinetic approach for light-cluster formation, we investigate the impact of explicit light-cluster degrees of freedom on collective flows in Au+Au collisions at FOPI energies with beam energies $E_{\rm beam}$= $120$--$1500 A$ MeV by using a density-, momentum-, and isospin-dependent N$5$LO Skyrme pseudopotential. We first benchmark the kinetic approach by comparing the calculated light-cluster yields with FOPI data in central Au+Au collisions. We then analyze the collective flows of protons and light nuclei (deuterons, tritons, $^{3}\mathrm{He}$, and $^{4}\mathrm{He}$) in mid-central collisions. For protons, calculations with and without dynamical light-cluster degrees of freedom are compared to quantify the influence of dynamical cluster formation on proton directed ($v_1$), elliptic ($v_2$), triangular ($v_3$), and quadrangular ($v_4$) flows. We find that the dynamical light-cluster effect appreciably modifies proton $v_1$--$v_4$ flows at $E_{\rm beam}=120$--$150 A$ MeV, remains visible at $E_{\rm beam}=250$--$400 A$ MeV, and gradually weakens at $E_{\rm beam}\gtrsim 600 A$ MeV. For light nuclei, the kinetic approach captures the overall beam-energy dependence of the FOPI flow data, with better agreement for $E_{\rm beam}\geq 400 A$ MeV. We further examine the nucleon-number scaling of $v_2/A$ in both model calculations and experimental data, finding that the kinetic light-cluster formation approach qualitatively reproduces the observed scaling behavior. These results highlight the importance of a dynamical treatment of light-cluster formation for interpreting collective flows in heavy-ion collisions below about $600 A$ MeV, although the clustering effects on proton flows are minor at higher collision energies.

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arXiv2026

Evaluation of U-235 and U-238 Fission Product Yields Using Bayesian Neural Networks: Comparison of Baseline and Physics-Informed Models

U-235 and U-238 are fundamental materials in thermal and fast neutron breeding studies. Accurate evaluation of their fission product yields is of critical importance for advanced reactor design and nuclear waste management. In this work, a baseline Bayesian neural network model (BNN0) with two hidden layers of 20 neurons each was constructed. An improved model, BNN3, was developed by incorporating additional physics-informed features, namely the odd-even effect, beta-decay energy, and isospin, into the network inputs. Comparative analyses of the general distributions of the fission yields and isotopic chain structures demonstrate that BNN3 exhibits significantly improved reconstruction accuracy and consistency with the target cumulative fission-yield distributions. For 16 representative fission products, the energy-dependent yield predictions of BNN3 show better agreement with both experimental data and evaluated libraries, accompanied by noticeably narrower confidence intervals. These results indicate that the incorporation of relevant physical information improves the model's sensitivity to underlying fission mechanisms and enhances its capability to reproduce the systematic characteristics of cumulative fission-yield distributions. Together, these strategies contribute to more accurate and robust nuclear data modeling, providing a methodological foundation for the evaluation and development of next-generation nuclear data libraries.

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arXiv2026

A unified classification-quantification framework for bubble-like nuclei within the extended quantum molecular dynamics model

A systematic study of relaxed low-energy cluster configurations for all nuclides listed in the AME2020 database is performed within the extended quantum molecular dynamics (EQMD) framework, with frictional cooling enabling stable relaxation. A unified classification-quantification framework based on the dimensionless parameters $BHTU$ is established to characterize bubble-like nuclear morphologies. The factor $B$, determined from the number of inflection points in the radial density profile, categorizes nuclei into droplet ($B=0$), bubble ($B=1$), and toroidal bubble ($B=2$). The parameter $H$ defines the degree of central density depletion, while $T$ and $U$ characterize the relative surface thickness and the relative size of the internal low-density region, respectively. Light nuclei are predominantly droplet-like with $B=0$, $H=0$, $T=1$, $U=0$. Most medium-mass nuclei have $B=1$, consistent with previous studies, especially in the vicinity of $^{40}$Ca and the neutron-rich region, where nuclei show a pronounced central hollowing with large $H$ and $U$ values, identifying them as prime candidates for experimental searches for bubble structures. Toroidal bubble nuclei ($B=2$), emerging for $Z\approx25$ and prevalent in heavy systems, display a local density minimum at intermediate radius together with a shell-like low-density region. Furthermore, bubble structures are found to be widespread in the superheavy region, in agreement with earlier studies. This parameter scheme not only reveals the morphological richness of nuclei but also establishes a predictive framework for exploring exotic nuclear shapes, thereby opening new avenues for future theoretical and experimental investigations.

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arXiv2026

Anisotropic flows in Au+Au collisions at $\sqrt{s_{\rm{NN}}} = 2.4\,\text{GeV}$ with a Skyrme pseudopotential

Within the framework of the lattice Boltzmann-Uehling-Uhlenbeck transport model, we present a systematic study of proton anisotropic flow observables measured by the HADES collaboration, by utilizing the recently developed density-, momentum- and isospin-dependent N$5$LO Skyrme pseudopotential. In particular, we investigate the impacts of the momentum dependence of nucleon mean-field potentials, the stiffness of symmetric nuclear matter (SNM) EOS, the high-density behaviors of the symmetry energy and the in-medium modification of nucleon-nucleon elastic cross sections on proton $v_{1}$, $v_{2}$, $v_{3}$, and $v_{4}$ in Au+Au collisions at $\sqrt{s_{\rm{NN}}} = 2.4\,\text{GeV}$. Our results show that the proton anisotropic flows are strongly sensitive to the momentum dependence of nucleon mean-field potential as well as the incompressibility coefficient $K_0$ of SNM. In addition, the transverse momentum dependence of the proton $v_2$ exhibits a modest sensitivity to the higher-order skewness coefficient $J_0$ and kurtosis coefficient $I_0$ of SNM as well as the momentum dependence of the symmetry potential, while the transverse momentum dependence of the proton $v_1$ is shown to modestly depend on the in-medium modification of nucleon-nucleon elastic cross sections. Moreover, the high-density symmetry energy seems to have limited effects on the proton anisotropic flows. These findings highlight the necessity of considering the momentum dependence of nucleon mean-field potentials including the symmetry potential, the higher-order characteristic parameters of SNM EOS beyond $K_0$, and the in-medium modification of nucleon-nucleon elastic cross sections, in future Bayesian transport model analyses on proton anisotropic flows in heavy-ion collisions at HADES energies, thereby to extract information on nuclear matter EOS as well as the associated underlying nuclear effective interactions.

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arXiv2025

Effects of mean-field momentum dependence on pion production in intermediate-energy heavy-ion collisions

Pion production in heavy-ion collisions at intermediate energies provides an important probe of the collision dynamics and nuclear matter equation of state, especially the high-density behavior of the symmetry energy. Using the lattice Boltzmann-Uehling-Uhlenbeck transport model with a recently developed nuclear effective interaction based on the so-called N$5$LO Skyrme pseudopotential, we investigate the effects of the momentum dependence of nucleon mean-field potentials on the pion production in Au+Au collisions at a beam energy of $1.23$~GeV/nucleon. We find that a stronger momentum dependence, for which the nucleon mean-field potentials increase faster with momentum, generally suppresses pion production. This feature can be understood in terms of the mean-field-induced modification of nucleon high-momentum phase space during the compression stage: a stronger momentum dependence can reduce the relative fraction of high-momentum nucleons in heavy-ion collisions, thereby suppressing the production of $Δ$ resonances and pions.

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arXiv2025

Atmospheric Antideuteron Flux Within a Dynamical Coalescence Approach

Cosmic antideuterons are considered as one of the most promising tools for the indirect detection of dark matter due to their ultra-low astrophysical backgrounds. Currently only upper limits on the antideuteron flux exist, but advancements in experimental detection technology may soon lead to positive signals. A major source of background is the production of secondary antideuterons through collisions of cosmic rays with the surrounding medium. In this study, antideuteron production is modeled using a multiphase transport model (AMPT) coupled with a dynamical coalescence model. By applying a widely used leaky box model and incorporating specific processes, we present a new theoretical baseline for atmospheric secondary antideuteron flux, including a tertiary contribution, from primary cosmic rays interacting with Earth's atmosphere. Our results indicate that the atmospheric antideuteron flux are within the range of various existing calculations and remain well below the upper limits set by the Balloon-borne Experiment with a Superconducting Spectrometer (BESS). The atmospheric antideuteron is found to dominate the antideuteron background at kinetic energies below $0.26 $ GeV/n.

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arXiv2025

Improved ion bunch quality of conical target irradiated by ultra-intense and ultra-short laser

We conduct particle-in-cell simulations to estimate the effects of circularly and linearly polarized SEL 100 PW lasers on flat Th targets with thicknesses of 50 nm, 100 nm and 250 nm, as well as easy to manufacture conical Th targets with angularity either on the left or right. As the thickness of the three types of targets increases and under the same polarized laser, the average energy, maximum energy and energy conversion efficiency of Th ions decrease as it is well-known, and except for the circularly polarized laser hit on the conical target with angularity on the left, the Th ion beam emittance also decreases, while its beam intensity increases conversely. The linearly polarized laser, compared to the circularly polarized laser with the same laser intensity, exhibits higher beam intensity, beam emittance and energy conversion efficiency for the same type and thickness of Th target. The conical Th target with angularity on the left and intermediate thickness, compared to the flat target and conical target with angularity on the right of the same thickness, possesses both higher ion average energy up to 7 GeV and virtually the same beam intensity up to 0.8 MA under the linearly polarized laser. The results lead us to an easier way of controlling laser-accelerated high-quality heavy ion beam by switching to an optimal laser-target configuration scheme, which may enable the synthesis of superheavy nuclei in a high-temperature and high-density extreme plasma environment in astronuclear physics.

physics.plasm-ph↗

arXiv2024

Bubble $^{36}$Ar and Its New Breathing Modes

The bubble nuclei are important components of exotic nuclear structures characterized by special depletions of central densities. Focusing on bubble structures of $^{36}$Ar, the characterizations of bubble nuclei were explored with the framework of the extended quantum molecular dynamics model. Three density distribution modes were uncovered for the first time, i.e. micro-bubble, bubble, and cluster resonances, which show unique spectral signature compared to the monopole resonance spectrum as the excitation intensity was increased in bubbles. Of pivotal importance is the revelation that the bubble mode's oscillation frequency closely resembles macroscopic bubble dynamics, building a connection between classical macroscopic phenomena and the quantum complexity of the nuclear structure. The discovery marks a crucial step forward in deciphering the relationship between classical and quantum domains within the enigmatic world of atomic nuclei.

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arXiv2024

Probing the internal structures of $pΩ$ and $ΩΩ$ with their production at the LHC

The strange dibaryons $pΩ$ ($^5\rm{S}_2$) and $ΩΩ$ ($^1\rm{S}_0$) are likely bound, existing either in molecular states like the deuteron or as more exotic compact six-quark states. Here, we investigate the production of these two dibaryons in Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV at the CERN Large Hadron Collider (LHC) within a covariant coalescence model, which employs a blast-wave-like parametrization for the phase-space configurations of constituent particles at freeze-out. For the molecular states, the $pΩ$ and $ΩΩ$ are produced via $p$-$Ω$ and $Ω$-$Ω$ coalescence, respectively, while for the six-quark states, they are formed through $uudsss$ and $ssssss$ coalescence. We find that the yield ratio $N_{pΩ}/N_Ω$ and $N_{ΩΩ}/N_Ω$ have a distinct centrality dependence between the molecular and multi-quark states, thus offering a promising way for distinguishing the two states. Our results suggest that the measurements of $pΩ$ and $ΩΩ$ production in relativistic heavy-ion collisions can shed light on their internal structures.

hep-ph↗

arXiv2022

Observing the Ping-pong Modality of Isospin Degree of Freedom in Cluster Emission from Heavy Ion Reactions

Two-body correlations of the isotope-resolved light and heavy clusters are measured in $^{86}$Kr+$^{\rm 208}$Pb reactions at 25 MeV/u. The yield and kinetic variables of the $A=3$ isobars, triton and $^3$He, are analyzed in coincidence with the heavy clusters of $7\le A \le 14$ emitted at the earlier chance. While the velocity spectra of both triton and $^3$He exhibit scaling behavior over the type of the heavy clusters, the yield ratios of ${\rm t/^3He}$ correlate reversely to the neutron-to-proton ratio $N/Z$ of the latter, showing the ping-pong modality of the $N/Z$ of emitted clusters. The commonality that the $N/Z$ of the residues keeps the initial system value is extended to the cluster emission in heavy ion reactions. The comparison of transport model calculations to the data is discussed.

nucl-ex↗

arXiv2021

Bayesian evaluation of residual production cross sections in proton induced spallation reactions

The Bayesian neural network (BNN) method is used to construct a predictive model for fragment prediction of proton induced spallation reactions with the guidance of a simplified EPAX formula. Compared to the experimental data, it is found that the BNN + sEPAX model can reasonably extrapolate with less information compared with BNN method. The BNN + sEPAX method provides a new approach to predict the energy-dependent residual cross sections produced in proton-induced spallation reactions from tens of MeV/u up to several GeV/u.

nucl-th↗

arXiv2020

A Bayesian-Neural-Network Prediction for Fragment Production in Proton Induced Spallation Reaction

Fragments productions in spallation reactions are key infrastructure data for various applications. Based on the empirical parameterizations {\sc spacs}, a Bayesian-neural-network (BNN) approach is established to predict the fragment cross sections in the proton induced spallation reactions. A systematic investigation have been performed for the measured proton induced spallation reactions of systems ranging from the intermediate to the heavy nuclei and the incident energy ranging from 168 MeV/u to 1500 MeV/u. By learning the residuals between the experimental measurements and the {\sc spacs} predictions, the BNN predicted results are in good agreement with the measured results. The established method is suggested to benefit the related researches in the nuclear astrophysics, nuclear radioactive beam source, accelerator driven systems, and proton therapy, etc.

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arXiv2018

Investigating the quark flavor dependence of the chiral magnetic effect with a multiphase transport model

Because the properties of the QCD phase transition and the chiral magnetic effect (CME) depend on the number of quark flavors ($N_{f}$) and quark mass, relativistic heavy-ion collisions provide a natural environment to investigate the flavor features if quark deconfinement occurs. We introduce an initial two-flavor or three-flavor dipole charge separation into a multiphase transport (AMPT) model to investigate the flavor dependence of the CME. By taking advantage of the recent ALICE data of charge azimuthal correlations with identified hadrons, we attempt to disentangle two-flavor and three-flavor CME scenarios in Pb+Pb collisions at 2.76 TeV. We find that the experimental data show a certain potential to distinguish the two scenarios, therefore we further suggest to collect more data to clarify the possible flavor dependence in future experiments.

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arXiv2018

Shannon Information Entropy in Heavy-ion Collisions

The general idea of information entropy provided by C.E. Shannon "hangs over everything we do" and can be applied to a great variety of problems once the connection between a distribution and the quantities of interest is found. The Shannon information entropy essentially quantify the information of a quantity with its specific distribution, for which the information entropy based methods have been deeply developed in many scientific areas including physics. The dynamical properties of heavy-ion collisions (HICs) process make it difficult and complex to study the nuclear matter and its evolution, for which Shannon information entropy theory can provide new methods and observables to understand the physical phenomena both theoretically and experimentally. To better understand the processes of HICs, the main characteristics of typical models, including the quantum molecular dynamics models, thermodynamics models, and statistical models, etc, are briefly introduced. The typical applications of Shannon information theory in HICs are collected, which cover the chaotic behavior in branching process of hadron collisions, the liquid-gas phase transition in HICs, and the isobaric difference scaling phenomenon for intermediate mass fragments produced in HICs of neutron-rich systems. Even though the present applications in heavy-ion collision physics are still relatively simple, it would shed light on key questions we are seeking for. It is suggested to further develop the information entropy methods in nuclear reactions models, as well as to develop new analysis methods to study the properties of nuclear matters in HICs, especially the evolution of dynamics system.

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arXiv2018

Pairing-energy coefficients of neutron-rich fragments in spallation reactions

The ratio of pairing-energy coefficient to temperature ($a_{p}/T$) of neutron-rich fragments produced in spallation reactions has been investigated by adopting an isobaric yield ratio method deduced in the framework of a modified Fisher model. A series of spallation reactions, 0.5$A$ and 1$A$ GeV $^{208}$Pb + $p$, 1$A$ GeV $^{238}$U + $p$, 0.5$A$ GeV $^{136}$Xe + $d$, 0.2$A$, 0.5$A$ and 1$A$ GeV $^{136}$Xe + $p$, and $^{56}$Fe + $p$ with incident energy ranging from 0.3$A$ to 1.5$A$ GeV, has been analysed. An obvious odd-even staggering is shown in the fragments with small neutron excess ($I\equiv N - Z$), and in the relatively small-$A$ fragments which have large $I$. The values of $a_{p}/T$ for the fragments, with $I$ from 0 to 36, have been found to be in a range from -4 to 4, and most values of $a_{p}/T$ fall in the range from -1 to 1. It is suggested that a small pairing-energy coefficient should be considered in predicting the cross sections of fragments in spallation reactions. It is also concluded that the method proposed in this article is not good for fragments with $A/A_{s} >$ 85\% (where $A_{s}$ is the mass number of the spallation system).

nucl-th↗

arXiv2017

Experimental Determination of One- and Two-Neutron Separation Energies for Neutron-Rich Copper Isotopes

A method is proposed to determine the one-neutron $S_n$ or two-neutron $S_{2n}$ separation energy of neutron-rich isotopes. Relationships between $S_n$ ($S_{2n}$) and isotopic cross sections have been deduced from an empirical formula, i.e., the cross section of an isotope exponentially depends on the average binding energy per nucleon $B/A$. The proposed relationships have been verified using the neutron-rich copper isotopes measured in the 64$A$ MeV $^{86}$Kr + $^{9}$Be reaction. $S_n$, $S_{2n}$, and $B/A$ for the very neutron-rich $^{77, 78, 79}$Cu isotopes are determined from the proposed correlations. It is also proposed that the correlations between $S_n$, $S_{2n}$ and isotopic cross sections can be used to find the location of neutron drip line isotopes.

nucl-ex↗

arXiv2017

Multinucleon transfer dynamics in heavy-ion collisions near Coulomb barrier energies

The multinucleon transfer reactions near barrier energies has been investigated with a multistep model based on the dinuclear system (DNS) concept, in which the capture of two colliding nuclei, the transfer dynamics and the de-excitation process of primary fragments are described by the analytical formula, the diffusion theory and the statistical model, respectively. The nucleon transfer takes place after forming the DNS and is coupled to the dissipation of relative motion energy and angular momentum by solving a set of microscopically derived master equations within the potential energy surface. Specific reactions of $^{40,48}$Ca+$^{124}$Sn, $^{40}$Ca ($^{40}$Ar, $^{58}$Ni)+$^{232}$Th, $^{40}$Ca ($^{58}$Ni)+$^{238}$U and $^{40,48}$Ca ($^{58}$Ni) +$^{248}$Cm near barrier energies are investigated. It is found that the fragments are produced by the multinucleon transfer reactions with the maximal yields along the $β$-stability line. The isospin relaxation is particularly significant in the process of fragment formation. The incident energy dependence of heavy target-like fragments in the reaction of $^{58}$Ni+$^{248}$Cm is analyzed thoroughly.

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