Showing 1–50 of 453 results for author: Ma, Y

Shedding Light on (Anti-)nuclei Production with Pion-Nucleus Femtoscopy

Authors: Li-Yuan Zhang, Che Ming Ko, Yu-Gang Ma, Qi-Ye Shou, Kai-Jia Sun, Rui Wang, Song Zhang

Abstract: High-energy nuclear collisions provide a unique environment for synthesizing both nuclei and antinuclei (such as $\bar{d}$ and $\overline{^4\text{He}}$) at temperatures ($k_BT\sim100$ MeV) nearly two orders of magnitude above their binding energies of a few MeV. The underlying production mechanism, whether through statistical hadronization, nucleon coalescence, or dynamical regeneration and disint… ▽ More High-energy nuclear collisions provide a unique environment for synthesizing both nuclei and antinuclei (such as $\bar{d}$ and $\overline{^4\text{He}}$) at temperatures ($k_BT\sim100$ MeV) nearly two orders of magnitude above their binding energies of a few MeV. The underlying production mechanism, whether through statistical hadronization, nucleon coalescence, or dynamical regeneration and disintegration, remains unsettled. By solving relativistic kinetic equations for pion-catalyzed reactions for deuteron regeneration and disintegration ($πNN \leftrightarrow πd$) in $pp$ collisions at $\sqrt{s}=13$ TeV, we find pronounced peaks in the femtoscopic momentum correlations of both $π^+-p$ and $π^+-d$ pairs. These peak structures originate from the formation of intermediate $Δ$ (1232) resonances, and their magnitudes agree with recent ALICE measurements when a downward in-medium $Δ$ mass shift of about 70 MeV/$c^2$ is included. In contrast, the nucleon coalescence model reproduces only about half of the observed peak strength, and the statistical hadronization model predicts no resonance feature. These findings from pion-nucleus femtoscopy provide compelling evidence that pion-catalyzed reactions play a dominant role in the production of light (anti-)nuclei in high-energy nuclear collisions and cosmic rays. △ Less

Submitted 13 November, 2025; originally announced November 2025.

Comments: 6 pages, 3 figures

Revisiting the Possibility of a Sharp Phase Transition in Cold Neutron Stars

Authors: Bao-Jun Cai, Bao-An Li, Yu-Gang Ma

Abstract: First-order phase transitions (FOPTs) in cold neutron stars (NSs) have been extensively studied and have provided valuable insights into the behavior of the densest matter visible in our Universe, although a strong consensus has yet to emerge. Revisiting the possibility of a hadron-quark FOPT from a new perspective, we examine the interplay between the coupled nature of gravity and microscopic int… ▽ More First-order phase transitions (FOPTs) in cold neutron stars (NSs) have been extensively studied and have provided valuable insights into the behavior of the densest matter visible in our Universe, although a strong consensus has yet to emerge. Revisiting the possibility of a hadron-quark FOPT from a new perspective, we examine the interplay between the coupled nature of gravity and microscopic interactions in Tolman--Oppenheimer--Volkoff (TOV) equations and the fundamental requirements of thermodynamic consistency in NSs. We demonstrate that a sharp FOPT manifested as a plateau in the equation of state (EOS) $P(\varepsilon)$, i.e., pressure $P$ versus energy density $\varepsilon$, is intrinsically incompatible with the regularity conditions of the TOV solutions. Although numerical integrations of the TOV equations with EOSs incorporating FOPTs may yield seemingly reasonable mass-radius relations consistent with current observations, such results can mask underlying inconsistencies. Our analysis thus establishes a structural consistency criterion for constraining dense-matter EOSs using NS observables, complementing existing studies of possible phase transitions in NS interiors. △ Less

Submitted 11 November, 2025; originally announced November 2025.

Comments: 9 pages with 2 figures

Chiral-scale effective field theory for dense and thermal systems

Authors: Jia-Ying Xiong, Yao Ma, Bing-Kai Sheng, Yong-Liang Ma

Abstract: We established a new power counting scheme, chiral-scale density counting (CSDC) rules, for the application of the chiral-scale effective field theory to nuclear matter at finite densities and temperatures. Within this framework, the free fermion gas is at the leading order, while one-boson-exchange interactions appear at the next-to-leading order, and the multi-meson couplings are at higher order… ▽ More We established a new power counting scheme, chiral-scale density counting (CSDC) rules, for the application of the chiral-scale effective field theory to nuclear matter at finite densities and temperatures. Within this framework, the free fermion gas is at the leading order, while one-boson-exchange interactions appear at the next-to-leading order, and the multi-meson couplings are at higher orders. Then, we applied the CSDC rules to study the nuclear matter properties, and estimated the valid regions of the CSDC rules. It was found that the zero temperature symmetric nuclear matter properties around saturation density and the critical temperature of liquid-gas phase transition can be captured by an appropriate choice of CSDC orders, and the results beyond these regions are align with the chiral nuclear force. Moreover, the evolution of scale symmetry was found to be consistent with previous studies. The results of this work indicate that the quantum corrections may be crucial in the studies of nuclear matter in a wide density region. △ Less

Submitted 6 November, 2025; originally announced November 2025.

Comments: 15 pages

The Trace Anomaly at Neutron Star Centers: Minimum or Not?

Authors: Bao-Jun Cai, Bao-An Li, Yu-Gang Ma

Abstract: While the equation of state (EOS) $P(\varepsilon)$ of neutron star (NS) matter has been extensively studied, the EOS-parameter $φ= P/\varepsilon$ or equivalently the dimensionless trace anomaly $Δ= 1/3 - φ$, which quantifies the balance between pressure $P$ and energy density $\varepsilon$, remains far less explored, especially in NS cores. Its bounds and density profile carry crucial information… ▽ More While the equation of state (EOS) $P(\varepsilon)$ of neutron star (NS) matter has been extensively studied, the EOS-parameter $φ= P/\varepsilon$ or equivalently the dimensionless trace anomaly $Δ= 1/3 - φ$, which quantifies the balance between pressure $P$ and energy density $\varepsilon$, remains far less explored, especially in NS cores. Its bounds and density profile carry crucial information about the nature of superdense matter. Physically, the EOS-parameter $φ$ represents the mean stiffness of matter accumulated from the stellar surface up to a given density. Based on the intrinsic structure of the Tolman--Oppenheimer--Volkoff equations, we show that $φ$ decreases monotonically outward from the NS center, independent of any specific input NS EOS model. Furthermore, observational evidence of a peak in the speed-of-sound squared (SSS) density-profile near the center effectively rules out a valley and a subsequent peak in the radial profile of $φ$ at similar densities, reinforcing its monotonic decrease. These model-independent relations impose strong constraints on the near-center behavior of the EOS-parameter $φ$, particularly demonstrating that the mean stiffness (or equivalently $Δ$) reaches a local maximum (minimum) at the center. △ Less

Submitted 5 November, 2025; originally announced November 2025.

Comments: 13 pages with 8 figures

Emergent Bell-Triplet State in Proton-Proton Scattering

Authors: Z. X. Shen, H. Y. Shang, Y. G. Ma, D. Bai, S. M. Wang, Z. C. Xu

Abstract: Entanglement is a fundamental resource in quantum information science, with profound implications for computing, communication, and metrology. Nuclear scattering processes, dominated by rich spin-dependent interactions, offer a natural platform for generating complex spin entanglement. Here, using proton-proton scattering as a quantum laboratory, we report the emergence of a near-pure Bell-triplet… ▽ More Entanglement is a fundamental resource in quantum information science, with profound implications for computing, communication, and metrology. Nuclear scattering processes, dominated by rich spin-dependent interactions, offer a natural platform for generating complex spin entanglement. Here, using proton-proton scattering as a quantum laboratory, we report the emergence of a near-pure Bell-triplet state at a laboratory energy of 151 MeV and a center-of-mass scattering angle of 90 degrees, with the spin amplitude a transition operator connecting two different Bell states. In contrast to the low-energy singlet state governed by the Pauli principle and the S-wave dominance, this second maximally entangled state is directly shaped by tensor forces beyond leading-order chiral effective field theory, providing a distinct quantum-information signature for realistic nuclear forces. These findings, invisible to traditional scattering observables, establish proton-proton scattering as a robust source of triplet entanglement and pave the way for next-generation nuclear Bell tests. △ Less

Submitted 28 October, 2025; originally announced October 2025.

Method to search for the triple-neutron state in an electron scattering experiment

Authors: Tianhao Shao, Jinhui Chen, Yu-Gang Ma, Josef Pochodzalla

Abstract: An electron scattering experiment to search for the trineutron state $^3n$ by reaction ${\rm ^4He}(e,~e'pπ^{+})^{3}n$ is designed for the A1 facility at Mainzer Microtron. The detailed principles, setup, and simulation of this experiment are presented. With the momenta of the scattered electron, the produced proton and $π^+$ from the reaction measured by three spectrometers with their triple coinc… ▽ More An electron scattering experiment to search for the trineutron state $^3n$ by reaction ${\rm ^4He}(e,~e'pπ^{+})^{3}n$ is designed for the A1 facility at Mainzer Microtron. The detailed principles, setup, and simulation of this experiment are presented. With the momenta of the scattered electron, the produced proton and $π^+$ from the reaction measured by three spectrometers with their triple coincidence, the missing mass spectrum of $^3n$ can be obtained. The production rate of $^3n$ based on the cross section of the reaction and a MC simulation is estimated to be about 1.5 per day, which can provide a confidence level of the signal greater than 5$σ$ with a beam time longer than 16 days. According to a MC simulation that evaluates the energy losses of particles in materials and the performance of three spectrometers, the estimated resolution and the predicted shape of the missing mass spectrum are presented. This work provides a new experimental concept for the search for multineutron states in future experiments with an electron beam. △ Less

Submitted 9 October, 2025; originally announced October 2025.

Comments: 8 pages, 5 figures

Journal ref: The European Physical Journal A, Volume 61, article number 230, (2025)

Singly heavy tetraquark resonant states with multiple strange quarks

Authors: Xin-He Zheng, Yao Ma, Shi-Lin Zhu

Abstract: We systematically investigate the S-wave singly heavy tetraquark systems containing two or three strange quarks, $Qs\bar{s}\bar{s}$, $Qn\bar{s}\bar{s}$ and $Qs\bar{s}\bar{n}\left( Q=c,b,n=u,d \right) $, within the constituent quark potential model. We solve the four-body Schrödinger equation using the Gaussian expansion method (GEM) and identify resonances via the complex scaling method (CSM). The… ▽ More We systematically investigate the S-wave singly heavy tetraquark systems containing two or three strange quarks, $Qs\bar{s}\bar{s}$, $Qn\bar{s}\bar{s}$ and $Qs\bar{s}\bar{n}\left( Q=c,b,n=u,d \right) $, within the constituent quark potential model. We solve the four-body Schrödinger equation using the Gaussian expansion method (GEM) and identify resonances via the complex scaling method (CSM). There are no bound states below the lowest two-meson thresholds. We obtain several compact resonances with $J^P=0^+,2^+$ in $Qs\bar{s}\bar{s}$, and $J^P=2^+$ in $Qn\bar{s}\bar{s}$ and $Qs\bar{s}\bar{n}$. The pole positions are mainly distributed around $7.0-7.2$ GeV (bottom) and $3.7-3.9$ GeV (charm), with widths from a few to several tens of MeV. These resonances decay into $D_sη^\prime ,{D_{(s)}^*}φ,{D_s}^*K^*$ and $D_s^*\bar{K}^*$ (and their bottom counterparts), providing targets for future experimental searches. △ Less

Submitted 1 October, 2025; originally announced October 2025.

Comments: 10 pages, 4 figures, 5 tables, comments are welcome

Tracing pT-differential radial flow from blast-wave analytics to quark coalescence

Authors: Jie Wan, Chun-Zheng Wang, Yu-Gang Ma, Qi-Ye Shou

Abstract: The observable $v_0(\pt)$, which quantifies event-by-event fluctuations in the differential transverse-momentum spectrum, is proposed as a direct and penetrating probe of radial flow in heavy-ion collisions. Recent measurements at the LHC exhibit a clear mass ordering for pions, kaons and protons at low \pt and a baryon-meson splitting at intermediate \pt, resembling to the well-known features of… ▽ More The observable $v_0(\pt)$, which quantifies event-by-event fluctuations in the differential transverse-momentum spectrum, is proposed as a direct and penetrating probe of radial flow in heavy-ion collisions. Recent measurements at the LHC exhibit a clear mass ordering for pions, kaons and protons at low \pt and a baryon-meson splitting at intermediate \pt, resembling to the well-known features of elliptic flow ($v_2$). In this letter, we first derive an analytic expression of $v_0(\pt)$ within a Blast-Wave framework incorporating fluctuations of freeze-out temperature and radial expansion velocity, which can naturally explains the experimentally observed mass ordering. The distinct dynamical origins of the mass ordering in $v_0(\pt)$ and $v_2(\pt)$ are discussed. Furthermore, using the AMPT model, we demonstrate that the baryon-meson splitting emerges spontaneously from the quark coalescence. This study provides deeper insight into the $v_0(\pt)$ observable and the collective dynamics of the QGP. △ Less

Submitted 29 September, 2025; originally announced September 2025.

Comments: 6 pages, 6 figures

Global Spin Alignment of (Anti-)$^4$Li in Non-Central Heavy-Ion Collisions

Authors: Yun-Peng Zheng, Dai-Neng Liu, Lie-Wen Chen, Jin-Hui Chen, Che Ming Ko, Yu-Gang Ma, Kai-Jia Sun, Jun Xu, Bo Zhou

Abstract: Non-central heavy-ion collisions produce hot and dense nuclear matter with significant fluid vorticity, which can induce global polarizations or alignments of particles with non-zero spins along the direction of the total orbital angular momentum. This phenomenon has been observed for hyperons and vector mesons in experiments. In the present study, we demonstrate that polarized nucleons lead to gl… ▽ More Non-central heavy-ion collisions produce hot and dense nuclear matter with significant fluid vorticity, which can induce global polarizations or alignments of particles with non-zero spins along the direction of the total orbital angular momentum. This phenomenon has been observed for hyperons and vector mesons in experiments. In the present study, we demonstrate that polarized nucleons lead to global spin alignment of the unstable nucleus $^4$Li, which can be measured through its strong decays via $^4\text{Li} \rightarrow {^3\text{He}} + p$. Assuming that $^4$Li is formed through the coalescence of polarized nucleons at kinetic freeze-out, we obtain the angular distribution of the daughter particle $^3$He in the rest frame of the polarized $^4$Li. Taking kinetically freeze-out nucleons from an isotropic and thermalized fireball of constant vorticity and including quantum corrections up to $\hbar^2$ in the coalescence calculation through the Moyal star product, we find that the angular distribution of $^3$He has a $\cos(2θ^*)$ dependence with $θ^*$ being its angle with respect to the quantization axis of $^4$Li. We also find that the $^3$He angular distribution depends on both the vorticity and the polarization of kinetically freeze-out nucleons. Future measurements on the spin alignment of $^4$Li in heavy-ion collisions thus offer a promising method to probe the spin dynamics, vortical structure, and spin-dependent equation-of-state of the nuclear matter produced in these collisions. △ Less

Submitted 18 September, 2025; originally announced September 2025.

Comments: 19 pages

Scaling approach to rigid and soft nuclear deformation through flow fluctuations in high-energy nuclear collisions

Authors: Lumeng Liu, Chunjian Zhang, Jinhui Chen, Jiangyong Jia, Xu-Guang Huang, Yu-Gang Ma

Abstract: The nature of octupole deformation, whether static or vibrational, remains an open question in nuclear physics. Here, we propose a scaling approach to probe this ambiguity by triangular flow fluctuations using multi-particle cumulants, $c_{3,\varepsilon}\{4\}$, in relativistic $^{238}$U+$^{238}$U collisions. We demonstrate that both $|c_{3,\varepsilon}\{4\}|$ and the ratio… ▽ More The nature of octupole deformation, whether static or vibrational, remains an open question in nuclear physics. Here, we propose a scaling approach to probe this ambiguity by triangular flow fluctuations using multi-particle cumulants, $c_{3,\varepsilon}\{4\}$, in relativistic $^{238}$U+$^{238}$U collisions. We demonstrate that both $|c_{3,\varepsilon}\{4\}|$ and the ratio $|c_{3,\varepsilon}\{4\}/c^2_{3,\varepsilon}\{2\}|$ scale linearly with the fourth-order moment of octupole deformation, $\langle β^4_{3,\mathrm{U}} \rangle$. Combined with the known linear relation of $c_{3,\varepsilon}\{2\}$ to $\langle β^2_{3,\mathrm{U}} \rangle$, this new relation provides a direct extraction of both the mean and variance of the octupole deformation fluctuations, finally discriminating between static and dynamic origins. This work establishes a new tool to probe the static and dynamic collective modes in high-energy nuclear collisions, advancing a significant step toward refining the initial conditions of quark-gluon plasma. △ Less

Submitted 11 September, 2025; originally announced September 2025.

Comments: 7 Pages, 5 figures

Assessing background effects in search of the chiral vortical effect in relativistic heavy-ion collisions

Authors: Chunzheng Wang, Jie Wan, Jinfeng Liao, Yugang Ma, Shuzhe Shi, Qiye Shou, Zhengqing Wang, Kegang Xiong, Song Zhang, Liang Zheng

Abstract: The search for the Chiral Vortical Effect (CVE) in relativistic heavy-ion collisions is carried out by measuring azimuthal correlators for baryon pairs such as $Λ$ and protons. Experimental results from the ALICE collaboration show significant separations in these observables, however, the interpretation remains unclear. It is believed that background contributions from baryon production mechanism… ▽ More The search for the Chiral Vortical Effect (CVE) in relativistic heavy-ion collisions is carried out by measuring azimuthal correlators for baryon pairs such as $Λ$ and protons. Experimental results from the ALICE collaboration show significant separations in these observables, however, the interpretation remains unclear. It is believed that background contributions from baryon production mechanisms may play an important role. Using three phenomenological models, the Blast Wave, AMPT, and AVFD+UrQMD, we systematically investigate the background effects in Pb--Pb collisions at \snn = 5.02 TeV. We demonstrate that local baryon conservation, as well as hadronic annihilation processes, can significantly influence the correlators. The feed-down contribution from secondary protons is also estimated. Our study provides a foundation for disentangling background mechanisms and further facilitates the search for the CVE. △ Less

Submitted 10 September, 2025; originally announced September 2025.

Comments: 9 pages, 4 figures

Origin of nucleon mass in the light of PSR J0614-3329 with quark-hadron crossover

Authors: Bikai Gao, Yuk-Kei Kong, Yong-Liang Ma

Abstract: The recent NICER observation of PSR J0614-3329, revealing the smallest reliably measured neutron star radius of $R = 10.29^{+1.01}_{-0.86}$ km at mass $M = 1.44^{+0.06}_{-0.07} M_\odot$, provides an unprecedented constraint on the equation of state of dense matter. We investigate the implications of this measurement for the origin of nucleon mass within the parity doublet model framework, which na… ▽ More The recent NICER observation of PSR J0614-3329, revealing the smallest reliably measured neutron star radius of $R = 10.29^{+1.01}_{-0.86}$ km at mass $M = 1.44^{+0.06}_{-0.07} M_\odot$, provides an unprecedented constraint on the equation of state of dense matter. We investigate the implications of this measurement for the origin of nucleon mass within the parity doublet model framework, which naturally incorporates both chiral variant and chiral invariant mass components. We construct unified equations of state by employing the parity doublet model with isovector scalar meson $a_0(980)$ for hadronic matter up to twice nuclear saturation density, smoothly connected to a Nambu-Jona-Lasinio-type quark model at higher densities through a crossover transition. By systematically varying the chiral invariant mass $m_0$ and quark matter parameters, we determine which values simultaneously satisfy all current astrophysical constraints, including gravitational wave observations from GW170817, NICER measurements of several pulsars, and the existence of two-solar-mass neutron stars. The inclusion of PSR J0614-3329 dramatically refines the allowed range of the chiral invariant mass from the previous constraint of $580~\text{MeV} \lesssim m_0 \lesssim 860~\text{MeV}$ to $800~\text{MeV} \lesssim m_0 \lesssim 860~\text{MeV}$, raising the lower bound by approximately 220 MeV. This result indicates that the chiral invariant mass must constitute at least 85\% of the nucleon mass, challenging the traditional picture of nucleon mass generation through spontaneous chiral symmetry breaking alone and highlighting the importance of gluon condensation and other non-chiral mechanisms. △ Less

Submitted 3 September, 2025; originally announced September 2025.

Dual-polarization structure and nuclear structure effect on $Λ$ polarization

Authors: X. G. Deng, Y. G. Ma

Abstract: We report a novel manifestation of spin-vorticity interplay in relativistic heavy-ion collisions. Using $^{16}$O+$^{197}$Au at $\sqrt{s_{\rm NN}}=7.7$ GeV as a test case, we show that the $Λ$ hyperon exhibits a clear dual-polarization structure, observed here in central $^{16}$O + $^{197}$Au collisions for the first time. The polarization is further highly sensitive to the intrinsic nuclear geomet… ▽ More We report a novel manifestation of spin-vorticity interplay in relativistic heavy-ion collisions. Using $^{16}$O+$^{197}$Au at $\sqrt{s_{\rm NN}}=7.7$ GeV as a test case, we show that the $Λ$ hyperon exhibits a clear dual-polarization structure, observed here in central $^{16}$O + $^{197}$Au collisions for the first time. The polarization is further highly sensitive to the intrinsic nuclear geometry: different $α$-cluster configurations of $^{16}$O, ranging from chain-like to tetrahedral, lead to distinct polarization patterns across centralities. In particular, the backward rapidity region and peripheral events display striking structure-dependent variations, including opposite angular distributions of local polarizations $P_x$ and $P_y$ compared with a spherical reference. These findings reveal that nuclear clustering leaves measurable imprints on hyperon spin alignment in relativistic collisions. Our results open a promising avenue for probing nuclear structure in short-lived systems and highlight a new spin-sensitive mechanism relevant for upcoming experiments at RHIC and future facilities. △ Less

Submitted 26 August, 2025; originally announced August 2025.

Comments: 6 pages, 4 figures

Finite density nuclear matter and neutron stars in hard-wall AdS/QCD model

Authors: Jun-Shuai Wang, Li-Kang Yang, Yin-Fang Liu, Yong-Liang Ma

Abstract: We investigate properties of nuclear matter, equation of state (EOS) of neutron stars and its mass-radius relation in a hard-wall AdS/QCD model by regarding baryons as solitonic configurations in gauge fields. Compared with previous approaches, we employ a different homogeneous approximation that takes into account the equations of motion for the pure gauge fields. By choosing appropriate paramete… ▽ More We investigate properties of nuclear matter, equation of state (EOS) of neutron stars and its mass-radius relation in a hard-wall AdS/QCD model by regarding baryons as solitonic configurations in gauge fields. Compared with previous approaches, we employ a different homogeneous approximation that takes into account the equations of motion for the pure gauge fields. By choosing appropriate parameters, we realize a chiral phase transition within the baryonic phase, where the chiral condensate decreases with the baryon chemical potential, until it reaches zero -- chiral symmetry is restored. In addition, independent of the existence of chiral phase transition, we also find that the speed of sound converges to the conformal limit at the density relevant to cores of massive stars but the trace of energy-momentum tensor does not vanish which indicates the pseudoconformal structure and intrinsic manifestation of scale symmetry in compact star matter. Through calculations, we obtain an equation of state that is more tightly constrained than previous works, and the resulting mass-radius relation of neutron stars is consistent with current observations. △ Less

Submitted 21 October, 2025; v1 submitted 26 August, 2025; originally announced August 2025.

Comments: 10 pages, 10 figures

Probing In-Medium Effect via Giant Dipole Resonance in the Extended Quantum Molecular Dynamics Model

Authors: Chen-Zhong Shi, Xiang-Zhou Cai, Yu-Gang Ma

Abstract: This article uses a stochastic approach to analyze the collision term, rather than the geometric method used in the original EQMD model, to examine the width of the isovector giant dipole resonance (GDR) in ${}^{208}$Pb. Based on the ``soft" EQMD model, the response and strength functions are self-consistently determined for various symmetry energy coefficient and in-medium reduction factor values… ▽ More This article uses a stochastic approach to analyze the collision term, rather than the geometric method used in the original EQMD model, to examine the width of the isovector giant dipole resonance (GDR) in ${}^{208}$Pb. Based on the ``soft" EQMD model, the response and strength functions are self-consistently determined for various symmetry energy coefficient and in-medium reduction factor values. The results confirm that the peak position and GDR width in ${}^{208}$Pb are highly sensitive to the symmetry energy and the in-medium nucleon-nucleon ({\it NN}) cross section. This provides an opportunity to study the nuclear equation of state (EoS) and the medium effect. A significant reduction in free {\it NN} elastic cross sections within the medium is necessary to accurately reproduce the GDR width, as demonstrated by a comparison with evaluation data. △ Less

Submitted 24 August, 2025; originally announced August 2025.

Comments: 9 pages, 7 figures

Influence of Cluster Configurations and Nucleon--Nucleon Scattering Cross-Section on Stopping Power in Heavy-Ion Collisions

Authors: S. Y. Yao, X. G. Deng, Y. G. Ma

Abstract: We investigate the impacts of nuclear $α$-clustering structures and nucleon--nucleon cross-section on nuclear stopping power for ${}^{16}\text{O}$ + ${}^{40}\text{Ca}$ collisions below 300 MeV/nucleon using an extended quantum molecular dynamics (EQMD) model. Our results show that the specific $α$-clustering configurations of ${}^{16}\text{O}$--including chain, square, kite, and tetrahedron--have… ▽ More We investigate the impacts of nuclear $α$-clustering structures and nucleon--nucleon cross-section on nuclear stopping power for ${}^{16}\text{O}$ + ${}^{40}\text{Ca}$ collisions below 300 MeV/nucleon using an extended quantum molecular dynamics (EQMD) model. Our results show that the specific $α$-clustering configurations of ${}^{16}\text{O}$--including chain, square, kite, and tetrahedron--have a significant effect on collision dynamics. Among them, the tightly bound tetrahedral structure exhibits the highest stopping power. Moreover, the repulsive Coulomb interaction is found to reduce the stopping power of protons in the Fermi-energy domain. At higher energies, the decreasing trend is influenced by both the nucleon--nucleon cross-section and the mean field. △ Less

Submitted 17 August, 2025; originally announced August 2025.

Comments: 8 pages, 7 figures

Journal ref: Physical Review C 112, 024605 (2025)

From Hyperons to Hypernuclei: A New Route to Unravel Proton Spin Polarization

Authors: Dai-Neng Liu, Yun-Peng Zheng, Wen-Hao Zhou, Jin-Hui Chen, Che Ming Ko, Yu-Gang Ma, Kai-Jia Sun, Song Zhang

Abstract: Ultra-relativistic nuclear collisions create the quark-gluon plasma (QGP) known as the hottest, least viscous, and most vortical fluid ever produced in terrestrial laboratories. Its vortical structure has been uncovered through the spin polarization of Lambda ($Λ$) hyperons, attributed to the spin-orbit coupling that transfers the system's orbital angular momentum to the quark spin, which is then… ▽ More Ultra-relativistic nuclear collisions create the quark-gluon plasma (QGP) known as the hottest, least viscous, and most vortical fluid ever produced in terrestrial laboratories. Its vortical structure has been uncovered through the spin polarization of Lambda ($Λ$) hyperons, attributed to the spin-orbit coupling that transfers the system's orbital angular momentum to the quark spin, which is then inherited by hadrons via quark recombination or coalescence. However, $Λ$ polarization reflects primarily the strange-quark component, leaving the spin dynamics of the up and down quarks largely unexplored. Although the proton is an ideal probe, its stability makes direct measurements experimentally challenging. Here, we propose to unravel proton spin polarization via hypertriton ($^3_Λ\text{H}$) measurements, exploiting the fact that spin information is preserved when polarized nucleons and $Λ$ coalesce to form hypertriton. We show that, over a broad range of collision energies, the polarizations of proton, $Λ$, and hypertriton are related by a simple linear scaling law. Since both $Λ$ and hypertriton polarizations can be measured via their self-analyzing weak decays, this linear relation provides a practical experimental avenue for accessing spin polarizations of protons and neutrons-the dominant baryonic degrees of freedom in nuclear collisions. △ Less

Submitted 21 August, 2025; v1 submitted 16 August, 2025; originally announced August 2025.

Comments: 11 pages, 3 figures

Probing Nucleon-$Ω_{\rm ccc}$Interaction via Lattice QCD at Physical Quark Masses

Authors: Liang Zhang, Takumi Doi, Yan Lyu, Tetsuo Hatsuda, Yu-Gang Ma

Abstract: We study the S-wave interactions between the nucleon ($N$) and the triply charmed Omega baryon ($Ω_{\mathrm{ccc}}$) using (2+1)-flavor lattice QCD with a physical pion mass ($m_π\simeq 137.1$ MeV) on a lattice volume $\simeq (8.1~\mathrm{fm})^3$. The charm quark is implemented with a relativistic heavy-quark action at its physical mass. Employing the time-dependent HAL QCD method, the $N$-… ▽ More We study the S-wave interactions between the nucleon ($N$) and the triply charmed Omega baryon ($Ω_{\mathrm{ccc}}$) using (2+1)-flavor lattice QCD with a physical pion mass ($m_π\simeq 137.1$ MeV) on a lattice volume $\simeq (8.1~\mathrm{fm})^3$. The charm quark is implemented with a relativistic heavy-quark action at its physical mass. Employing the time-dependent HAL QCD method, the $N$-$Ω_{\mathrm{ccc}}$ potentials in the spin-1 ($^3\mathrm{S}_1$) and spin-2 ($^5\mathrm{S}_2$) channels are extracted. In both channels, overall attraction is found with the scattering parameters, $a_0 = 0.56(0.13)\left(^{+0.26}_{-0.03}\right)$ fm and $r_{\mathrm{eff}} = 1.60(0.05)\left(^{+0.04}_{-0.12}\right)$ fm for the $^3\mathrm{S}_1$ channel, and $a_0 = 0.38(0.12)\left(^{+0.25}_{-0.00}\right)$ fm and $r_{\mathrm{eff}} = 2.04(0.10)\left(^{+0.03}_{-0.22}\right)$ fm for the $^5\mathrm{S}_2$ channel, indicating the absence of a dibaryon bound state. The extracted potentials are further decomposed into spin-independent and spin-dependent components. The spin-independent potential is a dominant component and features a short-range attractive core and a long-range attractive tail, while the spin-dependent potential shows short-range attraction (repulsion) in the spin-1 (spin-2) channel. Qualitative comparisons with previous studies of the $N$-$J/ψ$ and $N$-$Ω_{\rm{sss}}$ systems at $m_π\simeq 146$ MeV are provided, emphasizing the role of heavy-hadron chromo-polarizability arising from soft-gluon exchange between the nucleon and flavor-singlet hadrons. The charm quark mass dependence of the $N$-$Ω_{\rm ccc}$ potential is investigated as well. △ Less

Submitted 30 September, 2025; v1 submitted 14 August, 2025; originally announced August 2025.

Comments: 8 pages, 6 figures and 3 tables

Report number: RIKEN-iTHEMS-Report-25

Machine learning the single-$Λ$ hypernuclei with neural-network quantum states

Authors: Zi-Xiao Zhang, Yi-Long Yang, Wan-Bing He, Peng-Wei Zhao, Bing-Nan Lu, Yu-Gang Ma

Abstract: Single-$Λ$ hypernuclei are the most straightforward extension of atomic nuclei. A thorough description of baryonic system beyond first-generation quark sector is indispensable for the maturation of nuclear $ab$ $initio$ methods. This study pioneers the application of neural-network quantum states to hypernuclei, with trainable parameters determined by variational Monte Carlo approach (VMC-NQS). In… ▽ More Single-$Λ$ hypernuclei are the most straightforward extension of atomic nuclei. A thorough description of baryonic system beyond first-generation quark sector is indispensable for the maturation of nuclear $ab$ $initio$ methods. This study pioneers the application of neural-network quantum states to hypernuclei, with trainable parameters determined by variational Monte Carlo approach (VMC-NQS). In order to reduce the numerical uncertainty and treat the nucleons and hyperons in a unified manner, spinor grouping (SG) method is proposed to analytically integrate out isospin degrees of freedom. A novel spin purification scheme is developed to address the severe spin contamination occurring in standard energy minimization due to the weakly bound characteristic of light single-$Λ$ hypernuclei. The energy spectrum of $s$-shell hypernuclei is computed with one-thousandth level accuracy and benchmarked against existing stochastic variational results, showing superior performance. By comparing two different sets of Hamiltonian based on pionless effective field theory (pionless EFT), we choose an optimal model and further carry out calculations of selected $p$-shell charge-symmetric hypernuclei with mass number up to 13, exhibiting satisfactory consistency with experimental results. Our findings underscore the potential of VMC-NQS family in approaching exact solution of few-body systems and the accuracy of pionless EFT in modeling hypernuclei. This is crucial for understanding hyperon-nucleon-nucleon and hyperon-hyperon-nucleon interactions, providing a powerful tool for precisely predicting the properties of multi-strangeness hypernuclei. △ Less

Submitted 15 August, 2025; v1 submitted 5 August, 2025; originally announced August 2025.

Implication of neutron star observations to the origin of nucleon mass

Authors: Bikai Gao, Xiang Liu, Masayasu Harada, Yong-Liang Ma

Abstract: We investigate the implications of neutron star observations for understanding the origin of nucleon mass using a framework that combines three complementary approaches: the equation of state based on parity doublet structure for hadronic matter below $2n_0$, the Nambu-Jona-Lasinio (NJL) model for quark matter above $5n_0$, and a model-independent analysis of the intermediate density region based… ▽ More We investigate the implications of neutron star observations for understanding the origin of nucleon mass using a framework that combines three complementary approaches: the equation of state based on parity doublet structure for hadronic matter below $2n_0$, the Nambu-Jona-Lasinio (NJL) model for quark matter above $5n_0$, and a model-independent analysis of the intermediate density region based on fundamental physical principles. By systematically exploring parameter spaces and comparing theoretical predictions with recent observational constraints, we establish constraints on the chiral invariant mass. Our results suggest that more than a half of the nucleon mass originates from sources beyond spontaneous chiral symmetry breaking, challenging conventional understanding of nucleon mass generation. These constraints arise solely from fundamental physical principles and observational data, independent of specific assumptions about the nature of the quark-hadron transition, providing robust insights into the microscopic origin of hadron masses. △ Less

Submitted 31 July, 2025; originally announced August 2025.

Constraining neutron-proton effective mass splitting through nuclear giant dipole resonance within transport approach

Authors: Yi-Dan Song, Min-Si Luo, Rui Wang, Zhen Zhang, Yu-Gang Ma

Abstract: Based on the Boltzmann-Uehling-Uhlenbeck equation, we investigate the effects of the isovector nucleon effective mass $m^*_{v,0}$ and the in-medium nucleon-nucleon cross section $σ^*$ on the isovector giant dipole resonance~(IVGDR) in $^{208}{\rm Pb}$, employing a set of representative Skyrme energy density functionals. We find that the energy-weighted sum rule $m_1$ of the IVGDR is highly sensiti… ▽ More Based on the Boltzmann-Uehling-Uhlenbeck equation, we investigate the effects of the isovector nucleon effective mass $m^*_{v,0}$ and the in-medium nucleon-nucleon cross section $σ^*$ on the isovector giant dipole resonance~(IVGDR) in $^{208}{\rm Pb}$, employing a set of representative Skyrme energy density functionals. We find that the energy-weighted sum rule $m_1$ of the IVGDR is highly sensitive to $m^{*}_{v,0}$ and only mildly dependent on $σ^*$, while the width $Γ$ of the IVGDR is primarily governed by $σ^*$ with a moderate sensitivity to $m^*_{v,0}$. From a Bayesian analysis of both $m_1$ and $Γ$, we infer the isovector effective mass $m^{*}_{v,0}/m$ = $0.731^{+0.027}_{-0.023}$, where $m$ is the bare nucleon mass. Furthermore, by incorporating the isoscalar effective mass $m^*_{s,0}/m = 0.820 \pm 0.030$, extracted from the isoscalar giant quadrupole resonance in $^{208}{\rm Pb}$, the linear neutron-proton effective mass splitting coefficient at saturation density $ρ_0$ is determined to be $Δm^*_1 (ρ_0)/m = 0.200 ^{+0.101}_{-0.094}$. △ Less

Submitted 29 July, 2025; originally announced July 2025.

Comments: 10 pages, 5 figures

Heavy flavored hydrogen molecule systems

Authors: Hui-Min Yang, Yao Ma, Shi-Lin Zhu

Abstract: This study provides a comprehensive analysis of $S$-wave exotic hydrogen-like three-body systems ($ppμ^-$, $ppτ^-$, $μ^-μ^-p$, $τ^-τ^-p$, $pμ^-τ^-$) with spin-parity $J^P = 1/2^+$ and $3/2^+$, and four-body systems ($ppμ^-μ^-$, $ppτ^-τ^-$) with $J^P = 0^+$, $1^+$, and $2^+$. We use complex scaling and Gaussian expansion methods to solve the complex-scaled Schrödinger equation and obtain possible b… ▽ More This study provides a comprehensive analysis of $S$-wave exotic hydrogen-like three-body systems ($ppμ^-$, $ppτ^-$, $μ^-μ^-p$, $τ^-τ^-p$, $pμ^-τ^-$) with spin-parity $J^P = 1/2^+$ and $3/2^+$, and four-body systems ($ppμ^-μ^-$, $ppτ^-τ^-$) with $J^P = 0^+$, $1^+$, and $2^+$. We use complex scaling and Gaussian expansion methods to solve the complex-scaled Schrödinger equation and obtain possible bound and quasi-bound states. The resulting binding energies range from $-33.8$~keV to $-340$~eV. Notably, we present the first theoretical estimation of the bound-state energy levels of $ppμ^-μ^-$ and $ppτ^-τ^-$, which is of significant importance for understanding exotic few-body Coulomb systems. We further analyze spin configurations and root-mean-square radii to elucidate the spatial structure of these bound and quasi-bound states. Our results reveal that $K$-type spatial configurations play a crucial role in accurately describing bound and quasi-bound states in the hydrogen-molecule-like systems $ppμ^-μ^-$ and $ppτ^-τ^-$. Incorporating $K$-type configurations significantly alters the mass spectra of these states. Future muon colliders and muon facilities may offer promising platforms for the possible copious production of such heavy flavored hydrogen molecules and molecular ions. For instance, scattering processes such as $2μ^- + \mathrm{H_2} \to \mathrm{H_{2μ}} + 2e^-$, $μ^- + \mathrm{H_2} \to \mathrm{H_{μe}} + e^-$, and $μ^- + \mathrm{H_2^+} \to \mathrm{H_{2μ}^+} + e^-$ could be utilized, facilitating detailed studies of intriguing states such as $\mathrm{H_{2μ}}$, $\mathrm{H_{μe}}$, and $\mathrm{H_{2μ}^+}$. △ Less

Submitted 29 July, 2025; originally announced July 2025.

Comments: 13 pages, 9 figures, 6 tables, suggestions and comments welcome

Quantifying alpha clustering in the ground states of 16-O and 20-Ne

Authors: E. Harris, M. Barbui, J. Bishop, G. Chubarian, Sebastian Konig, E. Koshchiy, K. D. Launey, Dean Lee, Zifeng Luo, Yuan-Zhuo Ma, Ulf-G. Meissner, C. E. Parker, Zhengxue Ren, M. Roosa, A. Saastamoinen, G. H. Sargsyan, D. P. Scriven, Shihang Shen, A. Volya, Hang Yu, G. V. Rogachev

Abstract: Understanding the role of multi-nucleon correlations in the structure of light nuclei is at the forefront of modern nuclear science. In this letter, we present a quantitative benchmark study of alpha-cluster correlations in the ground states of 16-O and 20-Ne. Experimental data provide direct evidence that the wave functions of the ground states of 16-O and 20-Ne are dominated by alpha-cluster cor… ▽ More Understanding the role of multi-nucleon correlations in the structure of light nuclei is at the forefront of modern nuclear science. In this letter, we present a quantitative benchmark study of alpha-cluster correlations in the ground states of 16-O and 20-Ne. Experimental data provide direct evidence that the wave functions of the ground states of 16-O and 20-Ne are dominated by alpha-cluster correlations, in agreement with the predictions of sophisticated nuclear structure models. We also provide a new model-independent constraint for the alpha asymptotic normalization coefficient of the 16-O ground state and discuss the implications of these findings on the 12-C(alpha,gamma)16-O reaction, which is of critical importance for nuclear astrophysics. △ Less

Submitted 22 July, 2025; originally announced July 2025.

Comments: Main text: 6 pages, 2 figures, one table Supplemental materials: 4 pages, 5 figures

Alpha clustering in warm and dense nuclear matter from heavy-ion collisions

Authors: Rui Wang, Zhen Zhang, Yu-Gang Ma, Lie-Wen Chen, Che Ming Ko, Kai-Jia Sun

Abstract: Although light nuclear clusters are known to affect the properties of warm and dilute nuclear matter, their role in warm and dense nuclear matter remains unclear due to the lack of experimental evidence for their modifications by the Mott effect in such an environment. To address this issue, we resort to intermediate-energy heavy-ion collisions, where light clusters are mainly produced in the tran… ▽ More Although light nuclear clusters are known to affect the properties of warm and dilute nuclear matter, their role in warm and dense nuclear matter remains unclear due to the lack of experimental evidence for their modifications by the Mott effect in such an environment. To address this issue, we resort to intermediate-energy heavy-ion collisions, where light clusters are mainly produced in the transiently formed warm and dense matter. A kinetic approach, which includes dynamically the formation and dissociation of light clusters, is employed to deduce the strength of the Mott effects and the $α$-particle fraction in warm and dense nuclear matter from the light-nuclei yields measured by the FOPI Collaboration in central Au$+$Au collisions at energies of $0.25A$ to $0.6A~\rm GeV$. We find an unexpectedly abundant $α$ clustering in this environment, which will have profound implications for modeling the nuclear equation of state and describing supernovae and neutron star mergers. △ Less

Submitted 22 July, 2025; originally announced July 2025.

Comments: 6 pages, 3 figures

Composition of scalar mesons and their effects on nuclear matter properties in an extended linear sigma model

Authors: Yao Ma, Yong-Liang Ma

Abstract: It has been argued that the iso-scalar and iso-vector mesons play significant roles in nuclear matter and neutron star structures. We improve the extended linear sigma model with baryons, proposed in our previous work, by introducing the flavor structures constructed from antisymmetric tensors of chiral representations to study these physics. The parameter space of this model is refined with well-… ▽ More It has been argued that the iso-scalar and iso-vector mesons play significant roles in nuclear matter and neutron star structures. We improve the extended linear sigma model with baryons, proposed in our previous work, by introducing the flavor structures constructed from antisymmetric tensors of chiral representations to study these physics. The parameter space of this model is refined with well-reproduced nuclear matter properties at saturation density by the lowest order Lagrangian, ensuring consistency with vacuum results, such as $f_π\approx 134 \, \text{MeV}$. The anticipated plateau-like behaviors of the symmetry energy are predicted at intermediate densities, which is crucial for the consistency of GW170817 and the neutron skin thickness of $\text{Pb}^{208}$. Subsequently, neutron star structures are calculated using several parameter sets, and the results for the nuclear matter properties at saturation density align with empirical values. It is found that the neutron star structures are sensitive to the couplings between the iso-vector $a_0$ meson and nucleons and the four-vector meson couplings: small values of both are favorable. Meanwhile, nuclear matter properties at saturation density favor larger values of the latter and are not sensitive to the former. This signifies the statistical significance of neutron star observations when obtaining realistic chiral effective field theories or models at various densities. The parameter set favored by neutron star observations also aligns the behavior of the sound velocity with the conformal limit at high densities relevant to cores of massive stars. It is hoped that the results of this work can guide future studies on the relationship between the microscopic symmetry of strong interactions and macroscopic phenomena. △ Less

Submitted 5 October, 2025; v1 submitted 14 July, 2025; originally announced July 2025.

Two-flavor color superconductivity in a general Nambu-Jona-Lasinio model with color and charge neutrality

Authors: Li-Kang Yang, Di-Sheng Fan, Cheng-Ming Li, Yong-Liang Ma

Abstract: By using a general NJL model including as many interaction channels as possible, and taking into account the constraints imposed by color and charge neutrality, we analyze how the different interaction channels contribute to the charge-neutral two-flavor color-superconducting matter. After taking the Fierz transformation, the number of parameters in the NJL model is reduced and thereby quark-antiq… ▽ More By using a general NJL model including as many interaction channels as possible, and taking into account the constraints imposed by color and charge neutrality, we analyze how the different interaction channels contribute to the charge-neutral two-flavor color-superconducting matter. After taking the Fierz transformation, the number of parameters in the NJL model is reduced and thereby quark-antiquark condensates and diquark condensates are related. Through a self-consistent solution of the gap equations, we find that in addition to the diquark and vector channels, the scalar-isovector, vector-isovector, and vector-isovector-color-octet channels are also important, while other channels can be neglected. Moreover, between the normal quark matter phase and two-flavor color-superconducting phase, there is a gapless two-flavor color-superconducting phase. The fractions of quarks with different flavors and colors are calculated in both gaped and gapless two-flavor color-superconducting phases. In addition, We illustrate the phase diagrams in the diquark coupling and chemical potential plane, and discuss in detail how the dominant channels influence these phase diagrams. △ Less

Submitted 9 July, 2025; originally announced July 2025.

Comments: 12 pages, 13 figures

Particle species dependence of elliptic flow fluctuations in Pb-Pb collisions at LHC energies in a multiphase transport model

Authors: Jie Wan, Chun-Zheng Wang, Yu-Gang Ma, Qi-Ye Shou, Song Zhang

Abstract: The fluctuations of elliptic flow (\vtwo) in relativistic heavy-ion collisions offer a powerful tool to probe the collective behavior and transport properties of the quark-gluon plasma (QGP). The dependence of these fluctuations on particle species further sheds light on the hadronization mechanism. At LHC energies, the ALICE experiment has measured $v_2$ fluctuations for charged pions, kaons, and… ▽ More The fluctuations of elliptic flow (\vtwo) in relativistic heavy-ion collisions offer a powerful tool to probe the collective behavior and transport properties of the quark-gluon plasma (QGP). The dependence of these fluctuations on particle species further sheds light on the hadronization mechanism. At LHC energies, the ALICE experiment has measured $v_2$ fluctuations for charged pions, kaons, and (anti-)protons via the ratio of \vtwo measured with respect to the spectator plane (\vtwosp) and from the four-particle cumulants (\vtwofour). However, the observed dependencies on transverse momentum and particle type remain not fully understood. In this study, we perform a phenomenological investigation using a multiphase transport (AMPT) model, which allows us to trace the full evolution of flow fluctuations intertwined with the quark coalescence. The results qualitatively reproduce the ALICE measurements and offer deeper insights into the transport dynamics and hadronization of the QGP. △ Less

Submitted 6 July, 2025; originally announced July 2025.

Comments: 9 pages, 5 figures

Spin polarization from nucleon-nucleon scatterings in intermediate-energy heavy-ion collisions

Authors: Rong-Jun Liu, Jun Xu, Yu-Gang Ma

Abstract: We propose a new mechanism of generating spin polarization in heavy-ion collisions dominated by nucleon degree of freedom. By incorporating the spin change in nucleon-nucleon scatterings based on the phase shift data together with the constraint of rigorous angular momentum conservation and Pauli blocking, we illustrate through a Boltzmann-Uehling-Uhlenbeck transport model that appreciable spin po… ▽ More We propose a new mechanism of generating spin polarization in heavy-ion collisions dominated by nucleon degree of freedom. By incorporating the spin change in nucleon-nucleon scatterings based on the phase shift data together with the constraint of rigorous angular momentum conservation and Pauli blocking, we illustrate through a Boltzmann-Uehling-Uhlenbeck transport model that appreciable spin polarization (about $1 \sim 2\%$) can be generated in intermediate-energy heavy-ion collisions. This mechanism, together with the nuclear spin-orbit potential, may help to understand the spin polarization in few-GeV heavy-ion collisions dominated by nucleon degree of freedom. △ Less

Submitted 27 June, 2025; originally announced June 2025.

Comments: 6 pages, 4 figures

Journal ref: Physics Letters B 868, 139703 (2025)

Connecting dilaton thermal fluctuation with the Polyakov loop at finite temperature

Authors: Bing-Kai Sheng, Yong-Liang Ma

Abstract: Understanding the character of the deconfinement phase transition is one of the fundamental challenges in particle physics. In this work, we derive a formula for the expectation value of the Polyakov loop -- the order parameter of the deconfinement phase transition -- in pure $\mathrm{SU(N_{\mathrm{c}})}$ gauge systems at finite temperatures starting from the Coleman\textendash Weinberg-type effec… ▽ More Understanding the character of the deconfinement phase transition is one of the fundamental challenges in particle physics. In this work, we derive a formula for the expectation value of the Polyakov loop -- the order parameter of the deconfinement phase transition -- in pure $\mathrm{SU(N_{\mathrm{c}})}$ gauge systems at finite temperatures starting from the Coleman\textendash Weinberg-type effective potential encoding the trace anomaly of QCD. Our results are in good agreement with the Lattice QCD data and can effectively describe the large-$N_{\mathrm{c}}$ behaviors of the expectation value of the Polyakov loop. Notably, our findings predict the strongest first-order deconfinement phase transition as $N_{\mathrm{c}} \to +\infty$. Furthermore, to establish a relation between the dilaton field and the Polyakov loop, we also derive the scale transformation rule for temperature based on quantum statistical mechanics. The results of this work may shed a light on the connection between deconfinement phase transition and evolution of scale symmetry in the thermal system. △ Less

Submitted 16 June, 2025; originally announced June 2025.

Comments: 28 pages. Comments are welcome

New level density parameter beyond Egidy-Bucurescu's systematics

Authors: Junzhe Zhang, Yanan Zheng, Caixin Yuan, Yangyang Shen, Yingchen Mao

Abstract: Extending beyond the Egidy-Bucurescu systematics, the nuclear level density parameters (LDPs) for the back-shifted Fermi gas model were compiled. Three forms of LDPs were fitted: the liquid-drop model (LDM), the droplet model (DM), and the power-law dependence on mass number A. Additionally, the root-mean-square deviations (RMSDs) of the new LDPs and existing literature values were calculated. The… ▽ More Extending beyond the Egidy-Bucurescu systematics, the nuclear level density parameters (LDPs) for the back-shifted Fermi gas model were compiled. Three forms of LDPs were fitted: the liquid-drop model (LDM), the droplet model (DM), and the power-law dependence on mass number A. Additionally, the root-mean-square deviations (RMSDs) of the new LDPs and existing literature values were calculated. The newly fitted global LDM-type parameters outperform the commonly used Toke-Swiatecki parameters in various statistical model calculations. In contrast, neither the global nor the combined DM-type parameters yielded satisfactory results. Among the tested parameter sets, the widely adopted Reisdorf parameters exhibited the best overall performance, as evidenced by the larger number of experimental data points falling within their narrower RMSD confidence intervals. For the power-law A-dependence, the new global parameters performed better than the existing homogeneous ones. The ground-state deformation and isospin correction factors had minimal overall impact on the LDP fits. However, the current results suggest that theoretical calculations for transitional nuclei should account for ground-state deformation effects. △ Less

Submitted 2 June, 2025; originally announced June 2025.

Comments: 18 pages, 4 figures

The ${φNN,J/ψNN,η_c NN}$ systems based on HAL QCD interactions

Authors: Liang-Zhen Wen, Yao Ma, Lu Meng, Shi-Lin Zhu

Abstract: We investigate the existence of bound states and resonances in the ${φNN, J/ψNN, η_c NN}$ systems using HAL QCD interactions for ${φN, J/ψN}$, and ${η_c N}$. We employ the Gaussian expansion method to solve the complex-scaled Schrödinger equation and find no resonances or bound states in the ${J/ψNN}$ and ${η_c NN}$ systems. We estimate the interaction between charmonium and nuclei, concluding tha… ▽ More We investigate the existence of bound states and resonances in the ${φNN, J/ψNN, η_c NN}$ systems using HAL QCD interactions for ${φN, J/ψN}$, and ${η_c N}$. We employ the Gaussian expansion method to solve the complex-scaled Schrödinger equation and find no resonances or bound states in the ${J/ψNN}$ and ${η_c NN}$ systems. We estimate the interaction between charmonium and nuclei, concluding that the $J/ψ$ or $η_c$ is likely to bind with ${}^3\mathrm{H}$, ${}^3\mathrm{He}$, ${}^4\mathrm{He}$, and heavier nuclei. For the $φNN$ system, the lattice QCD $φN\left({ }^2 S_{1 / 2}\right)$ interaction is absent. We combine the $φp$ correlation function analysis and HAL QCD results in Model A. We assume the spin-spin interactions for $J/ψN$ and $φN$ systems are inversely proportional to their masses in Model B. Model A predicts a stronger $φN({}^2 S_{1/2})$ interaction and permits a two-body bound state, whereas Model B suggests the interaction is attractive but too weak to form a bound state. Both models predict bound states for the $I(J^P) = 0(0^-)$ and $0(1^-)$ $φNN$ systems. In Model A, these states are deeply bound with binding energies exceeding 15 MeV and remain existent when considering parameter uncertainties. In contrast, these states are very loosely bound in Model B, with binding energies below 1 MeV and an existent probability of about 60\% when parameter uncertainties are considered. In both models, there exist very loosely bound $I(J^P) = 0(2^-)$ three-body states which resemble a $φ$-d atom with the $φ$ meson surrounding the deuteron, but their existences are sensitive to parameter uncertainties. No bound states or resonances are found in the isovector $I(J^P) = 1(1^-)$ $φNN$ system. △ Less

Submitted 2 July, 2025; v1 submitted 14 March, 2025; originally announced March 2025.

Comments: 16 pages, 9 figures. Comments are welcome

Journal ref: Phys. Rev. D 111, 114004 (2025)

$t$+$t$ cluster states in $^{6}$He

Authors: W. H. Ma, D. Y. Tao, B. Zhou, J. S. Wang, Y. G. Ma, D. Q. Fang, W. B. He, Y. Y. Yang, J. B. Ma, S. L. Jin, P. Ma, J. X. Li, Y. S. Song, Q. Hu, Z. Bai, M. R. Huang, X. Q. Liu, Z. H. Gao, F. F. Duan, S. Y. Jin, S. W. Xu, G. M. Yu, T. F. Wang, Q. Wang

Abstract: The study of $t$+$t$ cluster states in $^{6}$He provides valuable insights into exotic nuclear structures and the behavior of fermionic cluster systems. This study shows rich cluster resonant state structures above the threshold, identified by experimental reconstruction and theoretical calculations. The excitation energy spectrum above the $t$+$t$ threshold in $^{6}$He is measured via the fragmen… ▽ More The study of $t$+$t$ cluster states in $^{6}$He provides valuable insights into exotic nuclear structures and the behavior of fermionic cluster systems. This study shows rich cluster resonant state structures above the threshold, identified by experimental reconstruction and theoretical calculations. The excitation energy spectrum above the $t$+$t$ threshold in $^{6}$He is measured via the fragmentation excitation process during the breakup reaction of $^{9}$Li on a $^{208}$Pb target at an incident energy of 32.7 MeV/nucleon. The resonant states are reconstructed from the final state coincident particles $t$+$t$ using the invariant mass method, while the non-resonant background is estimated using the event mixing method. The two new states of energy level peaks at $17.016\pm0.002$ and $19.4\pm0.6$ MeV are observed in addition to the previously observed energy level peaks at $13.9\pm0.3$ and $15.0\pm0.3$ MeV. Microscopic cluster model calculations exploring the $t+t$ resonance states in $^6\mathrm{He}$ yield theoretical energy spectra which are then compared with the current experimental results. The calculated reduced width amplitudes (RWA) of the $t+t$ channels further confirm the clustering structure of the identified $t+t$ resonance states. △ Less

Submitted 7 March, 2025; originally announced March 2025.

Comments: 9 pages, 7 figures, 1 table

Ab Initio Calculations of the Carbon and Oxygen Isotopes: Energies, Correlations, and Superfluid Pairing

Authors: Young-Ho Song, Myungkuk Kim, Youngman Kim, Kihyeon Cho, Serdar Elhatisari, Dean Lee, Yuan-Zhuo Ma, Ulf-G. Meißner

Abstract: We perform \textit{ab initio} nuclear lattice calculations of the neutron-rich carbon and oxygen isotopes using high-fidelity chiral interactions. We find good agreement with the observed binding energies and compute correlations associated with each two-nucleon interaction channel. For the isospin $T=1$ channels, we show that the dependence on $T_z$ provides a measure of the correlations among th… ▽ More We perform \textit{ab initio} nuclear lattice calculations of the neutron-rich carbon and oxygen isotopes using high-fidelity chiral interactions. We find good agreement with the observed binding energies and compute correlations associated with each two-nucleon interaction channel. For the isospin $T=1$ channels, we show that the dependence on $T_z$ provides a measure of the correlations among the extra neutrons in the neutron-rich nuclei. For the spin-singlet S-wave channel, we observe that any paired neutron interacts with the nuclear core as well as its neutron pair partner, while any unpaired neutron interacts primarily with only the nuclear core. For the other partial waves, the correlations among the extra neutrons grow more slowly and smoothly with the number of neutrons. These general patterns are observed in both the carbon and oxygen isotopes and may be universal features that appear in many neutron-rich nuclei. △ Less

Submitted 25 February, 2025; originally announced February 2025.

Comments: 14 pages, 10 figures

$α+α+{}^{3}$He cluster structure in ${}^{11}$C

Authors: Ying-Yu Cao, De-Ye Tao, Bo Zhou, Yu-Gang Ma

Abstract: We study the $α+ α+ {}^{3}$He cluster structure of ${}^{11}$C within the microscopic cluster model. The calculations essentially reproduce the energy spectra for both negative and positive parity states, particularly the $3/2_3^-$ state near the $α+α$+${}^{3}$He threshold. We also calculate the isoscalar monopole, electric quadrupole transition strengths, and root-mean-square radii for the low-lyi… ▽ More We study the $α+ α+ {}^{3}$He cluster structure of ${}^{11}$C within the microscopic cluster model. The calculations essentially reproduce the energy spectra for both negative and positive parity states, particularly the $3/2_3^-$ state near the $α+α$+${}^{3}$He threshold. We also calculate the isoscalar monopole, electric quadrupole transition strengths, and root-mean-square radii for the low-lying states. These results suggest that the $3/2_3^-$, $1/2_2^-$, and $5/2_3^-$ states have a well-developed $α+ α$ + ${}^{3}$He cluster structure. The analysis of the generator coordinate method wave functions indicates the dilute gaslike nature for the $3/2_3^-$, $1/2_2^-$, and $5/2_3^-$ states, suggesting that they could be candidates for the Hoyle-analog state. Furthermore, it is found that the $5/2_2^+$ and $5/2_3^+$ states may possess a linear chain structure. △ Less

Submitted 11 February, 2025; originally announced February 2025.

Comments: 12 pages, 8 figures

Journal ref: Phys. Rev. C 111, 024309 (2025)

Hoyle-analog state in ${}^{13}$N

Authors: Ying-Yu Cao, De-Ye Tao, Bo Zhou, Yu-Gang Ma

Abstract: We investigate the cluster structure of $\rm {}^{13}N$ using a microscopic $α+α+α+p$ four-body cluster model. The calculated spectra agree well with the observed spectra in the low-lying states. We calculate the reduced width amplitudes and spectroscopic factors to investigate the Hoyle-analog state in $\rm {}^{13}N$. Our calculations show that the $3/2_3^-$ state at $E_x=10.8$ MeV is primarily co… ▽ More We investigate the cluster structure of $\rm {}^{13}N$ using a microscopic $α+α+α+p$ four-body cluster model. The calculated spectra agree well with the observed spectra in the low-lying states. We calculate the reduced width amplitudes and spectroscopic factors to investigate the Hoyle-analog state in $\rm {}^{13}N$. Our calculations show that the $3/2_3^-$ state at $E_x=10.8$ MeV is primarily constituted by $\rm {}^{12}C(0^+_2)+\mathit{p}$ and $\rm {}^{9}B(3/2^-)+α$ components. This finding is generally consistent with the newly observed $3/2^-$ state at $E_x=11.3$ MeV via the $3α+ \mathit{p}$ decay channel. Moreover, considering the calculated root-mean-square radius and isoscalar monopole transition strengths, the $3/2_3^-$ state emerges as a candidate for the Hoyle-analog state with the $\rm {}^{12}C(0^+_2)+\mathit{p}$ cluster structure. △ Less

Submitted 30 January, 2025; originally announced January 2025.

Comments: 8 pages, 6 figures

Baryon Construction with $η^\prime$ Meson Field

Authors: Fan Lin, Yong-Liang Ma

Abstract: In the low-energy regime, baryons with $N_f \geq 2$ have long been constructed as skyrmions or through bag models, but such constructions for $N_f = 1$ are hindered by the trivial topological structure of the meson field. Recent proposals suggest that one-flavor baryons can instead be interpreted as quantum Hall droplets on the $η'$ domain wall, providing a potential link to quark--hadron continui… ▽ More In the low-energy regime, baryons with $N_f \geq 2$ have long been constructed as skyrmions or through bag models, but such constructions for $N_f = 1$ are hindered by the trivial topological structure of the meson field. Recent proposals suggest that one-flavor baryons can instead be interpreted as quantum Hall droplets on the $η'$ domain wall, providing a potential link to quark--hadron continuity at high density. In retrospect, the qualitative or semi-qualitative construction of one-flavor baryons on the $η'$ domain wall reveals that these baryons can be described as quantum Hall droplets, resembling topological solitons akin to skyrmions. Using an effective theory on the $η'$ domain wall, which is conjectured to be the Chern--Simons--Higgs theory, it is discussed that its vortex solution with unit baryon numbers naturally has a spin of $N_c/2$, and thus can be interpreted as a baryon or multi-baryon structure. The particle--vortex duality suggests that quarks carry a fractional topological charge of $1/N_c$ and obey fractional statistics. In terms of chiral bag models, confinement can be attributed to the monopoles confined within the bag, and the vector meson fields on the bag surface are essential for ensuring the correct baryon number in the chiral bag framework, thereby providing deeper insights into baryons as non-trivial topological structures of the meson field. In this paper, we review the progress in this development, with a special focus on the $η^\prime$ domain wall dynamics. Naive extensions to $N_f \geq 2$ are also discussed. △ Less

Submitted 24 March, 2025; v1 submitted 30 January, 2025; originally announced January 2025.

Comments: Published version

Journal ref: Symmetry 2025, 17, 477

Branching ratio and information entropy for the p+$^{12}$C reaction in the extended-quantum-molecular-dynamics model

Authors: Lei Shen, Bo-Song Huang, Yu-Gang Ma

Abstract: The reactions of p+$^{12}$C with triangular 3$α$ structure and spherical structure with incident energies ranging from 5 to 200 MeV/nucleon are simulated by the in the extended-quantum-molecular-dynamics (EQMD) model together with the GEMINI decay process. This paper presents the incident energy dependence of the branching ratios of fragment production and multiplicity, as well as the associated e… ▽ More The reactions of p+$^{12}$C with triangular 3$α$ structure and spherical structure with incident energies ranging from 5 to 200 MeV/nucleon are simulated by the in the extended-quantum-molecular-dynamics (EQMD) model together with the GEMINI decay process. This paper presents the incident energy dependence of the branching ratios of fragment production and multiplicity, as well as the associated event information entropy. The results indicate that the triangular 3$α$ $^{12}$C has an extra branching ratio for the quasi-elastic reaction compared to the spherical $^{12}$C. This peculiarity of the branching ratios of the triangular 3$α$ $^{12}$C appears as a small dent in the curves of the event information entropy (both the fragment information entropy and the multiplicity information entropy). Therefore, we propose that the event information entropy could be a probe for detecting the $α$-cluster structure. △ Less

Submitted 29 January, 2025; originally announced January 2025.

Comments: 9 pages, 7 figures

Journal ref: Physical Review C 111, 014606 (2025)

Confined Monopoles in Chiral Bag

Authors: Fan Lin, Yong-Liang Ma

Abstract: The chiral bag model offers a dual description of hadron physics in terms of quarks and hadrons in the sense of Cheshire Cat principle. In this work, we find that, within the chiral bag, confinement is likely caused by monopole condensation. The chiral bag surface can be interpreted as an $η'$ domain wall, where a dynamical Chern-Simons theory emerges. Under level-rank duality, the Chern-Simons th… ▽ More The chiral bag model offers a dual description of hadron physics in terms of quarks and hadrons in the sense of Cheshire Cat principle. In this work, we find that, within the chiral bag, confinement is likely caused by monopole condensation. The chiral bag surface can be interpreted as an $η'$ domain wall, where a dynamical Chern-Simons theory emerges. Under level-rank duality, the Chern-Simons theory serves as the counterterm introduced to block the so-called color charge leakage. To ensure the correct net baryon number of the full chiral bag, an additional Chern-Simons theory involving the vector meson field arises on the bag surface and extends outside the bag. This leads to a Chern-Simons-Higgs theory localized on the $η'$ domain wall, as previously conjectured. We also propose that the skyrmion description of baryons could be understood as a system of monopoles enveloped by a meson cloud. △ Less

Submitted 9 July, 2025; v1 submitted 27 January, 2025; originally announced January 2025.

Comments: Version published in Phys.Rev.D

Journal ref: Physical Review D 112, 014009 (2025)

Investigating the pion emission source in pp collisions using the AMPT model with sub-nucleon structure

Authors: Dong-Fang Wang, Mei-Yi Chen, Yu-Gang Ma, Qi-Ye Shou, Song Zhang, Liang Zheng

Abstract: The measurement of momentum correlations of identical pions serves as a fundamental tool for probing the space-time properties of the particle emitting source created in high-energy collisions. Recent experimental results have shown that, in pp collisions, the size of the one-dimensional primordial source depends on the transverse mass (\mt) of hadron pairs, following a common scaling behavior, si… ▽ More The measurement of momentum correlations of identical pions serves as a fundamental tool for probing the space-time properties of the particle emitting source created in high-energy collisions. Recent experimental results have shown that, in pp collisions, the size of the one-dimensional primordial source depends on the transverse mass (\mt) of hadron pairs, following a common scaling behavior, similar to that observed in Pb--Pb collisions. In this work, a systematic study of the \pipi source function and correlation function is performed using the multiphase transport model (AMPT) to understand the properties of the emitting source created in high multiplicity pp collisions at $\sqrt{s}=13$ TeV. The \mt scaling behavior and pion emission source radii measured by ALICE experiment can be well described the model with sub-nucleon structure. These studies shed new light on the understanding of the effective size of the \pipi emission source and on studying the intensity interferometry in small systems with a transport model. △ Less

Submitted 26 January, 2025; originally announced January 2025.

Comments: 10 pages, 11 figures

Study on the Distribution Amplitude of the Scalar Meson $K_0^*(1430)$

Authors: Chen Wang, Yuanyuan Ma, Zhijun Wang, Yanjun Sun

Abstract: Based on sum rules, we explore the twist-2 distribution amplitude of the $K_0^*(1430)$ meson, treating it as the ground state of a quark-antiquark system. We posit that the spacetime distance $x$ should be infinitesimally close to the quark separation $ z$. By incorporating quark distance corrections, with $x^2 \approx z^2 \approx x z$, the calculated moments yield additional insights. Moreover, w… ▽ More Based on sum rules, we explore the twist-2 distribution amplitude of the $K_0^*(1430)$ meson, treating it as the ground state of a quark-antiquark system. We posit that the spacetime distance $x$ should be infinitesimally close to the quark separation $ z$. By incorporating quark distance corrections, with $x^2 \approx z^2 \approx x z$, the calculated moments yield additional insights. Moreover, we employ light-cone sum rules to compute the form factors for the semi-leptonic decay process $B_s \rightarrow K$. The reliability of the computed distribution amplitude is confirmed through its comparison with the form factor. △ Less

Submitted 25 January, 2025; originally announced January 2025.

Comments: 14 pages,3 figures

The 3$α$ correlations of ground and excited $0^+$ states of $^{12}\mathrm{C}$ within the microscopic cluster model

Authors: De-Ye Tao, Bo Zhou, Yu-Gang Ma

Abstract: The cluster structures of the $0^+$ states in $^{12}\mathrm{C}$, including the ground state, the Hoyle state, and the recently identified $0_3^+$ and $0_4^+$ states, are analyzed to explore the cluster configurations and $3α$ correlations without assuming the existence of $^8\mathrm{Be}$. In particular, the key quantity -- two-cluster overlap amplitudes -- is calculated for the $3α$ clustering cha… ▽ More The cluster structures of the $0^+$ states in $^{12}\mathrm{C}$, including the ground state, the Hoyle state, and the recently identified $0_3^+$ and $0_4^+$ states, are analyzed to explore the cluster configurations and $3α$ correlations without assuming the existence of $^8\mathrm{Be}$. In particular, the key quantity -- two-cluster overlap amplitudes -- is calculated for the $3α$ clustering channels to reveal the essential features of these $0^+$ states. The results clearly show the distinction between the compact structure of the ground state and the gas-like structures of the excited $0^+$ states. The Hoyle state exhibits the expected gas-like dominant ($0S$) configuration, while the $0_3^+$ state shows a more extended $3α$ clustering structure, which can be viewed as a breathing-like excitation of the Hoyle state, with an additional nodal structure. The $0_4^+$ state is found to have a mixed configuration, featuring a bent-arm-like structure in the $S\otimes S$ channel and an enhanced $2α$ correlation in the $D\otimes D$ channel. △ Less

Submitted 18 January, 2025; originally announced January 2025.

Comments: 6 pages, 3 figures

Effects of inner crusts on $g$-mode oscillations in neutron stars

Authors: Hao Sun, Jia-Xing Niu, Hong-Bo Li, Cheng-Jun Xia, Enping Zhou, Yiqiu Ma, Ying-Xun Zhang

Abstract: In this work we investigate the influence of neutron stars' crusts on the non-radial $g$-mode oscillations and examine their correlations with nuclear matter properties fixed by adopting 10 different relativistic density functionals. At subsaturation densities, neutron star matter takes non-uniform structures and form the crusts. We find that the Brunt-Väisälä (BV) frequency increases significantl… ▽ More In this work we investigate the influence of neutron stars' crusts on the non-radial $g$-mode oscillations and examine their correlations with nuclear matter properties fixed by adopting 10 different relativistic density functionals. At subsaturation densities, neutron star matter takes non-uniform structures and form the crusts. We find that the Brunt-Väisälä (BV) frequency increases significantly at densities slightly above the neutron drip density (i.e., neutron stars' inner crusts), which leads to crust $g$-mode oscillations with their frequencies insensitive to the adopted density functional. At larger densities, BV frequency increases as well due to the core-crust transitions and emergence of muons, which lead to core $g$-mode oscillations. It is found that the obtained core $g$-mode frequencies generally increase with the slope of nuclear symmetry energy $L$, which eventually intersect with that of the crust $g$ modes adopting large enough $L$. This leads to the avoid-crossing phenomenon for the global $g$ modes that encompass contributions from both the crust and core. The correlation between the global $g_1$ mode and $L$ is identified for neutron stars with masses $M\gtrsim 1.4\ M_{\odot}$, which enables the measurements of $L$ based on gravitational wave observations. In our future study, the effects of the discontinuities in density or shear modulus should be considered, while the temperature, rotation, magnetic field, and superfluid neutron gas in neutron stars could also play important roles. △ Less

Submitted 10 May, 2025; v1 submitted 13 January, 2025; originally announced January 2025.

Journal ref: Phys. Rev. D 111, 103019 (2025)

Probing Nuclear Excitation by Electron Capture in an Electron Beam Ion Trap with Non-destructive Isomer Detection via Precision Mass Spectrometry

Authors: Bingsheng Tu, Nan Xue, Jialin Liu, Qi Guo, Yuanbin Wu, Zuoye Liu, Adriana Pálffy, Yang Yang, Ke Yao, Baoren Wei, Yaming Zou, Xiangjin Kong, Yu-Gang Ma

Abstract: Nuclear excitation by electron capture (NEEC) is an important nuclear excitation mechanism which still lacks conclusive experimental verification. This is primarily attributed to strong background x-/$γ$-ray noise and competing nuclear excitation processes which would overshadow the signals in various environments that NEEC takes place. Here, we propose an experimental approach to observe the NEEC… ▽ More Nuclear excitation by electron capture (NEEC) is an important nuclear excitation mechanism which still lacks conclusive experimental verification. This is primarily attributed to strong background x-/$γ$-ray noise and competing nuclear excitation processes which would overshadow the signals in various environments that NEEC takes place. Here, we propose an experimental approach to observe the NEEC process within a background-free environment. Through collisions with a highly-compressed mono-energetic electron beam in an electron beam ion trap, nuclei may get excited to a long-lived isomeric state via the NEEC process. Subsequently, ions can be extracted and Penning-trap mass spectrometry employed to unambiguously detect the isomer. Our study focuses on the promising candidate $^{189}\mathrm{Os}$, demonstrating measurable detection rates of the NEEC process and discussing the feasibility of the proposed approach. This new approach for observing the NEEC process may be realized in the near future. △ Less

Submitted 9 January, 2025; originally announced January 2025.

Analysis of clustering fragments of $^7$Li and $^7$Be in the microscopic cluster model

Authors: De-Ye Tao, Bo Zhou, Si-Min Wang, Yu-Gang Ma

Abstract: The nuclear structures of $^7$Li($α+n+n+p$) and $^7$Be($α+p+p+n$) are studied within the microscopic cluster model, in which the clustering fragments e.g., triton, $^3$He, and even the single nucleons around the core are studied in the $^7$Li and $^7$Be systems. We obtain the energy spectra and wave functions of $^7$Li and $^7$Be, and the calculated energy spectra of the ground states and some of… ▽ More The nuclear structures of $^7$Li($α+n+n+p$) and $^7$Be($α+p+p+n$) are studied within the microscopic cluster model, in which the clustering fragments e.g., triton, $^3$He, and even the single nucleons around the core are studied in the $^7$Li and $^7$Be systems. We obtain the energy spectra and wave functions of $^7$Li and $^7$Be, and the calculated energy spectra of the ground states and some of the excited states are consistent with experimental data. To investigate the cluster-formation probabilities, we calculate the reduced-width amplitudes of various binary partitions. The results show that the $α+t(^3\mathrm{He})$ cluster structure is dominant in the low-lying states of $^7$Li($^7$Be), including the ground state and the three lowest excited states. In some higher states around the single-particle thresholds, the components of $\mathrm{core}+N$ structures, namely $^6\mathrm{Li}+n$ and $^6\mathrm{He}+p$ in $^7$Li and $^6\mathrm{Li}+p$ in $^7$Be, are significantly enhanced. △ Less

Submitted 9 January, 2025; originally announced January 2025.

Comments: 11 pages, 5 figures

Validation and extrapolation of atomic mass with physics-informed fully connected neural network

Authors: Yiming Huang, Jinhui Chen, Jiangyong Jia, Lu-Meng Liu, Yu-Gang Ma, Chunjian Zhang

Abstract: Machine learning offers a powerful framework for validating and predicting atomic mass. We compare three improved neural network methods for representation and extrapolation for atomic mass prediction. The powerful method, adopting a macroscopic-microscopic approach and treating complex nuclear effects as output labels, achieves superior accuracy in AME2020, yielding a much lower root-mean-square… ▽ More Machine learning offers a powerful framework for validating and predicting atomic mass. We compare three improved neural network methods for representation and extrapolation for atomic mass prediction. The powerful method, adopting a macroscopic-microscopic approach and treating complex nuclear effects as output labels, achieves superior accuracy in AME2020, yielding a much lower root-mean-square deviation of 0.122 MeV in the test set, significantly lower than alternative methods. It also exhibits a better extrapolation performance when predicting AME2020 from AME2016, with a root-mean-square deviation of 0.191 MeV. We further conduct sensitivity analyses against the model inputs to verify interpretable alignment beyond statistical metrics. Incorporating theoretical predictions of magic numbers and masses, our fully connected neural networks reproduce key nuclear phenomena including nucleon pairing correlation and magic number effects. The extrapolation capability of the framework is discussed and the accuracy of predicting new mass measurements for isotope chains has also been tested. △ Less

Submitted 17 March, 2025; v1 submitted 2 January, 2025; originally announced January 2025.

Comments: 13 pages, 8 figures

Measurement of $\rm ^{6}H$ ground state energy in an electron scattering experiment at MAMI-A1

Authors: Tianhao Shao, Jinhui Chen, Josef Pochodzalla, Patrick Achenbach, Mirco Christmann, Michael O. Distler, Luca Doria, Anselm Esser, Julian Geratz, Christian Helmel, Matthias Hoek, Ryoko Kino, Pascal Klag, Yu-Gang Ma, David Markus, Harald Merkel, Miha Mihovilovič, Ulrich Müller, Sho Nagao, Satoshi N. Nakamura, Kotaro Nishi, Ken Nishida, Fumiya Oura, Jonas Pätschke, Björn Sören Schlimme , et al. (6 additional authors not shown)

Abstract: For the first time the neutron-rich hydrogen isotope $\rm ^{6}H$ was produced in an electron scattering experiment in the reaction $\rm ^{7}Li(e,~e'pπ^{+})^{6}H$ using the spectrometer facility of the A1 Collaboration at the Mainz Microtron accelerator. By measuring the triple coincidence between the scattered electron, the produced proton, and $π^{+}$, the missing mass spectrum of $\rm ^{6}H$ was… ▽ More For the first time the neutron-rich hydrogen isotope $\rm ^{6}H$ was produced in an electron scattering experiment in the reaction $\rm ^{7}Li(e,~e'pπ^{+})^{6}H$ using the spectrometer facility of the A1 Collaboration at the Mainz Microtron accelerator. By measuring the triple coincidence between the scattered electron, the produced proton, and $π^{+}$, the missing mass spectrum of $\rm ^{6}H$ was obtained. A clear peak above $^3$H+n+n+n energy threshold was seen resulting in a ground state energy of $\rm ^{6}H$ at $2.3\pm0.5({\rm stat.})\pm0.4({\rm syst.})$ MeV with a width of $1.9\pm1.0({\rm stat.})\pm0.4({\rm syst.})$ MeV. This work challenges the understandings of multi-nucleon interactions and presents a new method to study light neutron-rich nuclei with electron scattering experiments. △ Less

Submitted 31 March, 2025; v1 submitted 2 January, 2025; originally announced January 2025.

Comments: 6 pages, 4 figures

Nuclear matter properties from chiral-scale effective theory including a dilatonic scalar meson

Authors: Lu-Qi Zhang, Yao Ma, Yong-Liang Ma

Abstract: Chiral effective theory has become a powerful tool for studying the low-energy properties of QCD. In this work, we apply an extended chiral effective theory -- chiral-scale effective theory -- including a dilatonic scalar meson to study nuclear matter and find that the properties around saturation density can be well reproduced. Compared to the traditionally used Walecka-type models in nuclear mat… ▽ More Chiral effective theory has become a powerful tool for studying the low-energy properties of QCD. In this work, we apply an extended chiral effective theory -- chiral-scale effective theory -- including a dilatonic scalar meson to study nuclear matter and find that the properties around saturation density can be well reproduced. Compared to the traditionally used Walecka-type models in nuclear matter studies, our approach improves the behavior of symmetry energy and the incompressibility coefficient in describing empirical data without introducing additional freedoms. Moreover, the predicted neutron star structures fall within the constraints of GW170817, PSR J0740+6620, and PSR J0030+0451, while the maximum neutron star mass can reach about $~3M_{\odot}$ with a pure hadronic phase. Additionally, we find that symmetry patterns of the effective theory significantly impact neutron star structures. %In chiral-scale effective theory, effective operators are well organized by chiral-scale orders and freedoms induced by QCD symmetry patterns. We believe that introducing this type of theory into nuclear matter studies can lead to a deeper understanding of QCD, nuclear matter, and compact astrophysical objects. △ Less

Submitted 3 June, 2025; v1 submitted 25 December, 2024; originally announced December 2024.

Constraining the $DDD^*$ three-body bound state via the $Z_c(3900)$ pole

Authors: Hai-Xiang Zhu, Lu Meng, Yao Ma, Ning Li, Wei Chen, Shi-Lin Zhu

Abstract: In this study, we propose using the $Z_c(3900)$ pole position to constrain the existence of the $DDD^*$ three-body bound state within the one-boson-exchange (OBE) model. The existence of the $DDD^*$ bound state remains uncertain due to significant variations in the OBE interaction, particularly in the strength of scalar-meson-exchange interactions, which can differ by a factor about 20 between two… ▽ More In this study, we propose using the $Z_c(3900)$ pole position to constrain the existence of the $DDD^*$ three-body bound state within the one-boson-exchange (OBE) model. The existence of the $DDD^*$ bound state remains uncertain due to significant variations in the OBE interaction, particularly in the strength of scalar-meson-exchange interactions, which can differ by a factor about 20 between two commonly used OBE models. This discrepancy renders the $DDD^*$ system highly model-dependent. To address this issue, we constrain the scalar-meson-exchange interaction using the $Z_c(3900)$ pole position, where the pseudoscalar-meson coupling is well-determined, and the $ρ$- and $ω$-exchange interactions nearly cancel each other out, leaving the coupling constant of the $σ$-exchange as the only unknown parameter. Our results indicate that the isospin-$\frac{1}{2}$ $DDD^*$ bound states exist when $Z_c(3900)$ is a virtual state of $D\bar{D}^*/\bar{D}D^*$ located within approximately $-15$ MeV of the threshold. However, the three-body bound state is gone when the $Z_c(3900)$ virtual state pole is more than $20$ MeV away from the threshold. Each experimental progress, either on the $DDD^*$ state or the $Z_c(3900)$, can shed light on the nature of the other state. Another significant outcome is a refined set of OBE model parameters calibrated using the pole positions of $X(3872)$, $T_{cc}(3875)$, and $Z_c(3900)$, rigorously addressing the cutoff dependence. These parameters provide a valuable resource for more accurate calculations of systems involving few-body $D$, $D^*$ and their antiparticles. Additionally, we find no evidence of the $DDD^*$ three-body resonances after extensive search using a combination of the Gaussian expansion method and the complex scaling method. △ Less

Submitted 14 May, 2025; v1 submitted 17 December, 2024; originally announced December 2024.

Comments: 16 pages,8 figures;Accepted for publication in PRD

Journal ref: Phys. Rev. D 111, 094022 (2025)

Production of exotic hadrons in $pp$ and nuclear collisions

Authors: Jinhui Chen, Feng-Kun Guo, Yu-Gang Ma, Cheng-Ping Shen, Qiye Shou, Qian Wang, Jia-Jun Wu, Bing-Song Zou

Abstract: Exotic hadrons beyond the conventional quark model have been discovered in the past two decades. Investigations of these states can lead to deep understanding of nonperturbative dynamics of the strong interaction. In this concise review, we focus on the productions of exotic hadrons in $pp$, $p\bar p$, and nuclear collisions. Experimental observations of light nuclei and hypernuclei, as prototypes… ▽ More Exotic hadrons beyond the conventional quark model have been discovered in the past two decades. Investigations of these states can lead to deep understanding of nonperturbative dynamics of the strong interaction. In this concise review, we focus on the productions of exotic hadrons in $pp$, $p\bar p$, and nuclear collisions. Experimental observations of light nuclei and hypernuclei, as prototypes of hadronic molecules, in heavy ion collisions will also be briefly discussed. △ Less

Submitted 27 November, 2024; originally announced November 2024.

Comments: 17 pages, 16 figures. This review is dedicated to Professor Wenqing Shen on the occasion to celebrate his 80th birthday. All authors contributed equally to this work

Journal ref: Nucl. Sci. Tech. 36 (2025) 55

Reduced Basis Method for Few-body Bound State Emulation

Authors: R. Y. Cheng, K. Godbey, Y. B. Niu, Y. G. Ma, W. B. He, S. M. Wang

Abstract: Recent advances in both theoretical and computational methods have enabled large-scale, precision calculations of the properties of atomic nuclei. With the growing complexity of modern nuclear theory, however, also comes the need for novel methods to perform systematic studies and quantify the uncertainties of models when confronted with experimental data. This study presents an application of suc… ▽ More Recent advances in both theoretical and computational methods have enabled large-scale, precision calculations of the properties of atomic nuclei. With the growing complexity of modern nuclear theory, however, also comes the need for novel methods to perform systematic studies and quantify the uncertainties of models when confronted with experimental data. This study presents an application of such an approach, the reduced basis method, to substantially lower computational costs by constructing a significantly smaller Hamiltonian subspace informed by previous solutions. Our method shows comparable efficiency and accuracy to other dimensionality reduction techniques on an artificial three-body bound system while providing a richer representation of physical information in its projection and training subspace. This methodological advancement can be applied in other contexts and has the potential to greatly improve our ability to systematically explore theoretical models and thus enhance our understanding of the fundamental properties of nuclear systems. △ Less

Submitted 23 November, 2024; originally announced November 2024.

Comments: 8 pages, 5 figures