PaperPanorama

Nuclear Theory·nucl-th

Tuesday·February 24, 2026

16 papers9 primary·7 cross-listed

  1. 01

    [Submitted on 20 Feb 2026]

    Two-pion exchange nucleon-nucleon potentials with Roper resonance excitation

    Norbert Kaiser🇩🇪

    Motivated by the recent paper arXiv:2602.11815 [nucl-th], we calculate in these notes the spectral functions (i.e. imaginary parts) of the NN-potentials as they arise from -exchange with single and double Roper resonance excitation. In contrast to the full one-loop calculation, the spectral functions of the isoscalar and isovector central and tensor potentials can be given in simple analytical form. The pertinent momentum-space potentials are obtained via subtracted dispersion relations. This representation allows also to include a regulator function, that tames high-momentum components of the chiral -exchange. The calculation is extended to -exchange with combined -isobar and Roper resonance excitation.

    Comments:
    4 pages, 1 figure
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2602.18664 [pdf]
    1 citation
  2. 02

    [Submitted on 21 Feb 2026]

    Resolution-matched nuclear geometry and the nucleon-size ambiguity in relativistic heavy-ion collisions

    Hao-jie Xu🇨🇳

    Nuclear structure theory provides point-nucleon densities, whereas high-energy nuclear collisions probe nuclei through finite-resolution hadronic interactions. This resolution mismatch becomes a physical ambiguity when point densities are embedded in Monte Carlo initial-state models with a finite transverse nucleon profile. A parameter intended to describe the effective interaction range can then also reshape the nuclear surface, blurring the separation between nuclear structure and collision dynamics. I show that this ambiguity can largely account for the strong nucleon-width dependence of the Pb+Pb hadronic cross section () reported in recent Bayesian analyses. Fixing the folded density that enters the Glauber phase shift removes this ambiguity at the level of nuclear geometry. The corrected cross section becomes nearly insensitive to a Gaussian nucleon width and instead probes the nuclear surface. Within a two-component estimate for Pb, the current experimental uncertainty of translates into a broad neutron-skin interval, fm. These results reframe as a surface-sensitive bridge between point-nucleon nuclear structure and finite-resolution high-energy initial conditions, rather than as a standalone nucleon-size observable. This establishes resolution matching as a necessary step for using relativistic heavy-ion collisions as quantitative probes of nuclear structure.

    Comments:
    11 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2602.18683 [pdf]
    2 citations
  3. 03

    [Submitted on 22 Feb 2026]

    Constraining the nuclear symmetry energy with electric dipole polarizability and neutron skin characteristics in \texorpdfstring{}{208Pb} within antisymmetrized molecular dynamics

    Dandan Niu · Xinyu Wang · Ying Cui · Qiang Zhao · Kai Zhao · Akira Ono · Yingxun Zhang

    The electric dipole polarizability and the neutron-skin thickness of are two powerful and clean probes for constraining the symmetry energy at subsaturation densities. Within the framework of the antisymmetrized molecular dynamics (AMD) model, the width of the strength function and its dynamical origins are understood, and the and data favor effective interaction parameter sets with -34 MeV and -87 MeV. In addition, our calculations show that the sensitive densities of and range from 0.2 to 0.57, and the corresponding values of the symmetry energy at the lower and upper ends of this sensitive density region are MeV and MeV.

    Comments:
    13 pages, 8 figures, accepted by Physical Review C
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2602.19039 [pdf]
    PRC(2026)·1 citation
  4. 04

    [Submitted on 22 Feb 2026]

    Probing the structure of pygmy dipole resonance with its gamma decay

    W.-L. Lv · Y.-F. Niu · G. Colò

    The isospin properties and the collectivity of the pygmy dipole resonance (PDR) are long-standing open questions in nuclear structure studies. To answer these questions, the -decay of PDR states in Pb to the low-lying state is investigated using the Skyrme particle-vibration coupling (PVC) model. It is found that the decay from the PDR states to the low-lying state is strongly suppressed compared to that from the isovector giant dipole resonance (IVGDR), which reveals the predominantly isoscalar character of PDR. A detailed decomposition of the decay diagrams of the amplitudes of the processes contributing to the decay demonstrates the non-negligible presence of the 1 particle-1 hole configurations coupled to the phonon in the PDR wave function. Furthermore, we give a quantitative way to identify the components of complex-configurations in the wave function, and it is found that such component in PDR is smaller than that in IVGDR and much smaller than that in isoscalar giant quadrupole resonance (ISGQR).

    Comments:
    7 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2602.19052 [pdf]
    PRC(2026)·1 citation
  5. 05

    [Submitted on 22 Feb 2026]

    Charmonium suppression in fixed target proton-nucleus collisions

    Sourav Kanti Giri🇮🇳 · Partha Pratim Bhaduri🇮🇳 · Biswarup Paul🇮🇳 · Santosh K. Das🇮🇳

    In this article, we perform a systematic investigation of the cold nuclear matter (CNM) effects, operative on charmonium (, ) production, in fixed target proton-nucleus (p+A) collisions. Influence on charmonium production cross section due to the interplay of three different plausible CNM effects namely the initial-state parton energy loss, nuclear shadowing, and final-state absorption of the resonant states, are evaluated in detail. The available data on charmonium production in fixed target p+A collision experiments from SPS, Fermilab and HERA-B are examined for this purpose. The beam energy dependence of the observed production patterns are utilized to anticipate level of "normal" absorption in the upcoming proton induced collisions by the NA60+ experiment at CERN SPS and the CBM experiment at FAIR SIS100 accelerator facilities.

    Comments:
    22 pages, 20 figures. Version accepted for publication in EPJC
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2602.19072 [pdf]
    EPJC(2026)·1 citation
  6. 06

    [Submitted on 22 Feb 2026]

    Nuclear Pasta and Crustal Quasi-Periodic Oscillations in Neutron Star

    Vishal Parmar · Ignazio Bombaci

    We investigate the impact of nuclear pasta on crustal structure and torsional oscillations using a Bayesian ensemble of unified neutron-star equations of state based on relativistic mean-field models constrained by nuclear experiments, empirical saturation properties, chiral effective field theory, and multimessenger observations. For each posterior sample, we compute the pasta sequence within a compressible liquid-drop model and quantify the onset density, thickness, and mass fraction of the pasta layers. We show that the appearance and extent of nuclear pasta are primarily controlled by the symmetry-energy slope parameter . While spherical and rod-like pasta configurations are present for all equations of state, only a small fraction of the posterior supports slab, tube, or bubble geometries. The transition from spherical nuclei to rods is tightly constrained to occur at a density of . We further predict that the nuclear pasta layer occupies a relative radial thickness of and contributes a relative mass fraction of . Using the resulting crust models, we present the first quasi-periodic oscillations (QPOs) analysis based on a Bayesian posterior ensemble of neutron-star equations of state and systematically assess their compatibility with observed low-frequency quasi-periodic oscillations. We find that the predicted QPO frequencies are strongly correlated with the curvature of the symmetry energy evaluated at sub-saturation density, , and that uncertainties in the equation of state translate into a range of angular indices consistent with the observed frequencies.

    Comments:
    12 pages, 9 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
    arXiv:
    2602.19125 [pdf]
    PRD(2026)·2 citations
  7. 07

    [Submitted on 23 Feb 2026]

    Microscopic Optical Potential from Brueckner-Hartree-Fock Theory

    Miao Qi · Li-Li Chen · Li-Gang Cao · Feng-Shou Zhang · Xin-Le Shang · Wei Zuo · U. Lombardo

    Modern Brueckner-Hartree-Fock (BHF) calculations are very successful in describing various properties of symmetric and asymmetric nuclear matter. Within BHF theory a microscopic optical potential (MOP) for nucleon-nucleus scattering is developed. First, we parametrize the energy and density dependence of complex optical potentials in nuclear matter based on BHF calculations and then we construct the MOP for finite nuclei with the local density approximation extended to include the finite-range effects. The density distribution and the spin-orbit contribution are calculated from the Hartree-Fock (HF) approximation with LNS5 Skyrme interaction, the latter being constrained by the BHF results. The central real and imaginary potentials turn out to be quantitatively consistent with the phenomenological global Koning-Delaroche (KD) potentials. The performance of MOP is evaluated by considering neutron/proton scattering on Ca. The elastic scattering differential cross sections, analyzing powers and total/reaction cross sections are analyzed in the energy below 200 MeV. A good agreement between the theoretical results and the measurements is achieved. Since our results are presented in the analytic forms, they can thus be used easily in the analysis of the experimental data of the nucleon scattering on exotic nuclei.

    Comments:
    14 pages, 8 figures, 5 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2602.19465 [pdf]
    PRC(2026)·0 citations
  8. 08

    [Submitted on 23 Feb 2026]

    A Boson exchange approach for Helium Burning Stars

    Theodoros Depastas · Aldo Bonasera

    Helium burning plays a key role in the hierarchy of stellar nucleosynthesis and evolution, as the archetype of a bosonic 3-body system. Here, we examine the kinetic and nuclear aspects of the 3 reaction, under the auspices of the Thomas-Efimov theorem. Due to the 92.08 keV ground state of Be, multiple -cluster resonances appear especially at the lowest temperature (Thomas State), while with increasing temperature the system is dominated by the Hoyle/Efimov state. We extend our previous methodology for the sequential channel to describe the direct mechanism, that results in an equilateral geometry similar to the Thomas state. This is accomplished by developing a general approach to the N-body scattering, via successive particle-exchanging 2-body collisions, which eliminates long range Coulomb complications, in a similar manner to the Thomas-Efimov mechanism. We furthermore, discuss the ee decay of the compound state with a perturbation based methodology. Due to the symmetry of the system and the resulting reaction rates, we favor the E0 decay scheme over the E2. The E0 reaction rates obey all the available astrophysical and nuclear constraints and are compared to theoretical data from the literature, whose limitations are discussed. Our extended methodology provides a physically sound description of the debated low temperature region.

    Comments:
    8 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2602.19515 [pdf]
    PLB(2026)·0 citations
  9. 09

    [Submitted on 23 Feb 2026]

    Investigation of the Bound State via the \( K^{-} + {}^{3}\mathrm{He} \) Reaction

    Sajjad Marri🇮🇷 · Ahmad Naderi Beni🇮🇷

    Using the four-body Alt-Grassberger-Sandhas (AGS) equations for the \( K^{-}ppn \) system, we investigate the possible formation of a \( K^{-}pp \) quasi-bound state through the low-energy \( K^{-} + {}^{3}\mathrm{He} \) reaction. The neutron missing mass spectrum in the final state was calculated for different models of the \( \bar{K}N \) interaction. The results indicate that, irrespective of the specific nature of the \( \Lambda(1405) \) structure or the details of the \( \bar{K}N \) interaction model, a signal corresponding to the \( K^{-}pp \) quasi-bound state could appear in the \( \pi \Sigma p \) mass spectrum. This supports the feasibility of observing the \( K^{-}pp \) cluster in low-energy kaon-induced reactions on helium-3.

    Comments:
    11 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2602.19716 [pdf]
    EPJA(2026)·1 citation
  10. 10

    [Submitted on 20 Feb 2026] (cross-list from cond-mat.str-el)

    Analytic continuation of Green's functions with a neural network

    Fakher Assaad · Johanna Erdmenger · Anika Götz · René Meyer · Martin Rackl · Yanick Thurn

    An important problem in many-body physics is to reconstruct the spectral density from the imaginary-time domain Green's function. Typically, the imaginary-time Green's function is generated by Monte Carlo methods. As the one-point fermionic kernel diverges exponentially for large frequencies, numerical noise generically causes instabilities. We use a convolutional neural network to obtain the spectral density for a given imaginary time Green's function. The network is trained by data which we generate using random Gaussians. We improve the training data set available by including collision centers for the Gaussians rather than employing uniformly distributed Gaussians. Our network is constructed in such a way that its output fulfills positive semidefiniteness. We compare the results of our network with results of the Maximum Entropy method (MaxEnt), a standard method for the same reconstruction problem for the spectral density. This comparison is performed for three different cases, namely our Gaussian based test data as well as two physical models, the 1d Hubbard model showing spin-charge separation, and the two-dimensional SSH model in the self-consistent Born approximation. We find that the network outperforms MaxEnt when presented data close to the training set. For the physical models considered, MaxEnt recognizes physical features more precisely as compared to our network prediction. While it is hard to improve MaxEnt, the quality of the network depends on the training data set which can be systematically enhanced and improved.

    Comments:
    15 pages, 4 figures, 1 table
    Subjects:
    Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2602.18561 [pdf]
    0 citations
  11. 11

    [Submitted on 22 Feb 2026] (cross-list from astro-ph.HE)

    Evidence of Nuclear Urca Process in the Ocean of Neutron-Star Superburst MAXI J1752457

    Hao Huang · Akira Dohi · Amira Aoyama · Tomoshi Takeda · Nobuya Nishimura

    We propose that the rapid cooling of the neutron star following its X-ray superburst in MAXI J1752457 over a period of 4 days, observed by two Japanese satellites, MAXI and NinjaSat, is due to enhanced neutrino emission from cycles of electron capture and decay involving odd- nuclei (or Urca pairs) in the ocean. Hence, this work provides the first indication of the possible existence of such a ``nuclear Urca process". The observation of MAXI J1752457 implies a hot ignition layer with a maximum temperature of , located near the Urca shell in the ocean, such that the nuclear Urca process becomes dominant for up to days after the superburst. This behavior is distinct from that of normal Type-I X-ray bursts, which are triggered by hydrogen or helium burning in much shallower layers than those of superbursts. Our findings enable probing of superburst ashes through Urca pairs via long-term monitoring of crust cooling on day-long timescales.

    Comments:
    6 pages, 4 figures
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2602.19018 [pdf]
    1 citation
  12. 12

    [Submitted on 22 Feb 2026] (cross-list from hep-ph)

    Two nearby states in the region: Resolving the radiative-decay ratio tension with

    Satoshi X. Nakamura (Shandong University)🇨🇳

    Recently, LHCb reported the radiative-decay ratio extracted from . This result differs markedly () from the BESIII value obtained from , . Such a significant tension suggests that more than one state in the region contributes to the processes. We therefore propose a two-state scenario: a shallow bound state with and a charmonium candidate, , slightly above the threshold. We show that this hypothesis consistently describes these ratios along with other branching fractions and lineshapes across multiple processes. By contrast, fits without the component fail to reproduce the radiative-ratio data. We also predict helicity-angle distributions that motivates the future experiments to test the two-state hypothesis and search for the so-far missing .

    Comments:
    15 pages, 6 figures, 8 tables, figures added, published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    2602.19165 [pdf]
    PRD(2026)·2 citations
  13. 13

    [Submitted on 23 Feb 2026] (cross-list from hep-ph)

    Three-body molecular states composed of and two nucleons

    Si-Yi Chen🇨🇳 · Fei-Yu Chen🇨🇳 · Xu-Liang Chen🇨🇳 · Lu Meng🇨🇳 · Ning Li🇨🇳 · Wei Chen🇨🇳

    We study the three-body systems and within a hadronic molecular framework by combining a realistic nucleon-nucleon interaction with a potential constrained by heavy-quark symmetry. The three-body Schrödinger equation is solved with the Gaussian Expansion Method, and the analytic structure of the spectrum is investigated using the Complex Scaling Method. We find that the system supports a robust and compact bound state in the channel over a broad range of cutoff values, even when the corresponding subsystem is weakly bound or unbound. For , the spin- nature of the heavy meson and the associated spin-dependent forces generate a clear spin hierarchy: deeply bound states appear in both and channels, while the channel exhibits a characteristic two-branch pattern with a strongly bound compact branch and a more weakly bound, spatially extended branch. The root-mean-square radii indicate pronounced spatial compression compared with the deuteron scale, highlighting the cooperative roles of realistic correlations, the interactions, and heavy-quark symmetry in forming compact heavy-flavor few-body bound states. No three-body resonances under complex scaling are found in the explored parameter space. Our results provide quantitative benchmarks for future experimental searches for such charmed-meson-nuclear bound states.

    Comments:
    14 pages, 7 figures, 4 tables, accepted for publication in Physical Review D
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    2602.19504 [pdf]
    PRD(2026)·1 citation
  14. 14

    [Submitted on 23 Feb 2026] (cross-list from hep-ph)

    2025 EIC-France Workshop: Physics Highlights and Perspectives

    F. Arleo · V. Bertone · J. Bettane · B. Blossier · F. Bock · F. Bossù · R. Boussarie · F. Bouyjou · O. Brand-Foissac · N. L. Bucuru Rodriguez · V. Calvelli · P. Caucal and 66 other authors

    This document presents a synthesis of the theory contributions and discussions from the 2nd EIC-France Workshop, held at IJCLab (Orsay) on 1-3 December 2025. The workshop brought together members of the French hadron-physics community to review recent theoretical developments relevant to the future Electron-Ion Collider (EIC) and to coordinate national efforts in preparation for its early physics program. The report first summarizes the collider's initial running conditions and luminosity performance, as outlined in the EIC Early Science Matrix. It then provides concise overviews of the theoretical presentations on inclusive, semi-inclusive, exclusive, heavy-flavor, and small-x physics. Based on these discussions, two measurements emerged as especially well suited for early EIC operation and strongly aligned with areas of established French expertise: inclusive diffraction and inclusive quarkonium production. These channels offer clean signatures, robust theoretical interpretability, and direct sensitivity to fundamental QCD phenomena such as gluon saturation, heavy-quark dynamics, and the small-x structure of hadrons and nuclei. In addition, the workshop identified longer-term physics opportunities that will benefit from the full capabilities of the EIC after its ramp-up phase. These include accessing the three-dimensional structure of the pion through the Sullivan process and a broader program of exclusive three-body final states, both of which represent high-impact avenues for exploring hadronic structure and non-perturbative QCD. Together, the elements summarized in this report provide a coherent overview of the strategic priorities and scientific ambitions shaping the French community's contribution to the EIC physics program.

    Comments:
    10 pages, excluding the title page, author list, acknowledgements, and references; 6 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2602.19664 [pdf]
    0 citations
  15. 15

    [Submitted on 23 Feb 2026] (cross-list from hep-ph)

    Thermodynamically consistent treatment of repulsive corrections in HRG

    Somenath Pal🇮🇳

    We reformulate the treatment of density-dependent chemical potential shifts appearing in excluded-volume implementations of the hadron resonance gas model. An auxiliary classical representation is constructed in which a common energy shift is determined by preserving the scalar number density, ensuring thermodynamic consistency. Hadron radii are parametrized through a liquid-drop inspired mass-radius relation with two parameters: the pion radius and a scaling exponent. The resulting framework reproduces lattice QCD results for lower-order conserved-charge susceptibilities at zero chemical potentials with only two adjustable parameters.

    Comments:
    7 pages, 5 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2602.19821 [pdf]
    0 citations
  16. 16

    [Submitted on 23 Feb 2026] (cross-list from hep-ph)

    Unquenched Charmonium and Beyond

    Zi-Yue Bai🇨🇳 · Dian-Yong Chen🇨🇳 · Qi-Huang · Xiang Liu🇨🇳 · Si-Qiang Luo🇨🇳 · Jun-Zhang Wang🇨🇳

    The year 2024 marked the 50th anniversary of the discovery of the particle, which unveiled the charm quark and the charmonium spectrum, instigating the "November Revolution" in particle physics. This discovery catalyzed the development of quenched potential models, most notably the Cornell model, which provided a foundational quantitative description of the hadronic spectrum. However, the landscape of hadron spectroscopy has been profoundly transformed since the turn of the 21st century with the observation of numerous charmonium-like states, such as , which exhibit properties starkly at odds with quenched model predictions. These discrepancies, exemplified by the " low-mass puzzle" and the " problem" associated with vector states like , underscore the critical limitations of the quenched approximation and signal the necessity for a new theoretical paradigm. This review synthesizes recent advances in hadronic spectroscopy, arguing that the unquenched picture, which incorporates coupled-channel effects such as hadronic loops, is essential for a unified description of these new states and associated anomalies. We demonstrate how unquenched effects provide compelling solutions to long-standing puzzles in charmonium decays (e.g., the " puzzle" and anomalous dipion transitions), predict and explain the existence of exotic charged states like and via mechanisms such as Initial Single Pion Emission, and offer a framework for understanding interactions between charmonia and with nucleons. Furthermore, we emphasize the universality of unquenched effects, extending their application to bottomonium and light-flavor sectors. As experimental precision continues to improve, we advocate for the systematic development of unquenched hadronic spectroscopy.

    Comments:
    217 pages, 134 figures, 21 tables, accepted by Physics Reports
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    2602.19887 [pdf]
    24 citations

Affiliations

first authorsco-authorsvia INSPIRE