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Nuclear Theory·nucl-th

Thursday·August 13, 2026

13 papers—9 primary·4 cross-listed

All13Primary9Cross-lists4
  1. 01

    [Submitted on 11 Aug 2026]

    Nuclear level density studied in odd-mass nuclei in the framework of the projected shell model

    Jiaqi Wang · Saumi Dutta · Cui-Juan Lv · Long-Jun Wang · Yang Sun

    In a recent article [Phys. Rev. C 108, 034309 (2023)], we proposed a projected shell model method for the calculation of nuclear level density (NLD) in deformed even-even nuclei. The current article presents the subsequent study of NLDs in odd-mass nuclei as well as a comparative analysis between our calculated NLDs in adjacent even-even and odd-A systems. Since one nucleon in the odd-mass system remains blocked from participating in the pair formation, resulting in a weakened pairing (assessed by a smaller BCS pairing gap), pronounced differences between the NLDs in an odd-mass (both even-odd and odd-even) nucleus and its immediate even-even neighbour have been found. In general, the structure-dominated variations, which were found to be prominent in the even-even NLD at low energies, are greatly suppressed in the odd-mass systems. Specifically, from excitation energy as low as 2 MeV, the calculated densities of odd-parity and even-parity levels in odd-mass nuclei show an equal division signaling faster attainment of the statistical behavior. Nuclear level-spin distributions of both parities have been seen to adopt a regular Gaussian shape earlier than that found in the even-even system. Moreover, the pleasant property of our shell-model results, that each of our calculated levels is an eigenstate of angular momentum, allows us to extract the values of the energy-dependent dispersion of Ericson's spin-distribution formula and plot , the energy-, spin-, and parity-dependent level density.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.11347 [pdf]
    PRC(2025)·5 citations
  2. 02

    [Submitted on 11 Aug 2026]

    Projected shell model description of nuclear level density: Collective, pair-breaking, and multiquasiparticle regimes in even-even nuclei

    Jiaqi Wang · Saumi Dutta · Long-Jun Wang · Yang Sun

    There is overwhelmingly experimental evidence indicating that excited nuclear states are dominated by quasiparticle (qp) excitations, which form many-body configurations with broken nucleon-pairs from different orbitals. By using these multi-qp states as building blocks for a shell-model basis, we propose a novel shell-model method to calculate the nuclear level density (NLD) in deformed nuclei. The shell-model diagonalization with two-body residual interactions yields a large ensemble of eigenstates of angular momentum and parity. We demonstrate that NLD as a statistical quantity depends sensitively on the structure of deformed single-particle states. As the first example to introduce this method, we take a well-deformed rare-earth nucleus, Dy, for which NLD has been studied extensively by the Oslo method. By a quantitative comparison with discrete levels from spectroscopic measurements, we show that while the pronounced stepwise structure in the low-energy NLD curve can be understood as the collective excitation and nucleon-pair breaking, the exponential growth of levels in the higher-energy NLD can be described by the combination of the broken-pair states, subject to the Pauli principle. According to the nature of NLD with increasing excitation, we divide the entire NLD curve into (1) collective regime, (2) pair-breaking regime, and (3) multi-qp regime. We discuss the formation mechanism and characteristic features of NLD for the three regimes. In addition, the parity dependence and angular-momentum dependence in NLD are investigated with a strong emphasis on the structure effect.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.11374 [pdf]
    PRC(2023)·12 citations
  3. 03

    [Submitted on 12 Aug 2026]

    Variational neural-network solution of the two-body proton-halo problem with a Coulomb--Whittaker tail

    Lucas A. Souza · Tobias Frederico

    We present a variational artificial neural-network (VANN) solution of F in a two-body O potential model. The calculation uses a standard interaction from the literature as a controlled benchmark for testing whether a neural variational ansatz can reproduce not only bound-state energies and interior wave functions, but also the Coulomb--Whittaker tails that control halo and peripheral-capture observables. The reduced radial wave function is obtained by minimizing the Rayleigh quotient of the radial Schrödinger Hamiltonian with the constraints required by each partial wave. Because the variational energy can converge before the asymptotic normalization is correct, the ansatz combines a neural interior with the charged-particle Coulomb--Whittaker form. In the channel, the Pauli-forbidden component is computed and the physical one-node branch is checked independently for forbidden-state contamination. The Coulomb--Whittaker-constrained VANN reproduces independent Numerov benchmarks for the compact ground state and the extended halo state in energy, nodes, rms radius, and overlap. The compact-state ANC agrees to within one percent, while the halo ANC differs by about , within the larger numerical sensitivity of the asymptotic extraction. The continuum scattering states are obtained by standard Numerov integration with Coulomb matching; only the bound states are represented by the neural ansatz. Combined with these -wave scattering states, the VANN bound states yield astrophysical factors consistent with published benchmarks and data within the accuracy of the adopted two-body model. The results demonstrate the usefulness of physically constrained neural wave functions for tail-sensitive nuclear calculations and identify the asymptotic region as the most sensitive part of the calculation.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.11600 [pdf]
    Few Body Syst.(2026)·0 citations
  4. 04

    [Submitted on 12 Aug 2026]

    Calculation of tetraneutron-induced reaction cross sections with optical and Hauser-Feshbach statistical models

    Hiroyuki Fujioka · Toshihiko Kawano

    Interactions of tetraneutrons, which are assumed to be produced in the nuclear fission process, with nuclei are studied in the framework of optical and Hauser-Feshbach statistical models. It predicts a large probability of production for the tetraneutron-induced reaction on compared to other isotopes. The same technique is applied to the tetraneutron-induced reaction on and the hexaneutron-induced reaction on natural zinc to revisit two historical multi-neutron experiments performed in the past.

    Comments:
    16 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.11961 [pdf]
    EPJA(2026)·0 citations
  5. 05

    [Submitted on 12 Aug 2026]

    Four-neutron halo model at the unitary limit

    R. M Francisco🇧🇷 · D. S. Rosa🇧🇷 · G. Hupin🇫🇷 · T. Frederico🇧🇷 · M. T. Yamashita🇧🇷

    In some neutron-rich nuclei usually treated as two-neutron halos, the core can itself be resolved into a subcore-neutron-neutron subsystem, so that four valence neutrons may be involved. To describe this situation, a four-neutron halo model in the unitary limit is developed and applied to C, B, and Be, in which a compact nuclear core is surrounded by two weakly bound spin-singlet neutron pairs occupying different spatial shells, characterized by two independent momentum scales, with the four-neutron wave function fully antisymmetrized. The evolution of the halo structure with the ratio of the two scales is mapped from the limit of well-separated scales, where the system reduces to an effective two-neutron halo around a structured core, to the regime of comparable scales, where the four-neutron character is fully developed. At intermediate ratios, a window is identified in which the dimensionless root-mean-square distances become insensitive to the scale hierarchy and the system behaves approximately as a one-scale configuration. The calculated matter radii of C and B are consistent with the most recent experimental values and, within current uncertainties, the matter radius does not discriminate between an effective two-neutron-halo and an explicit four-neutron-halo description of C. Distinguishing the two pictures requires observables sensitive to the shape of the halo distribution, such as ratios of higher radial moments. For Be, the computed charge radius is consistent with the value derived from the measured point-proton radius.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.11964 [pdf]
    0 citations
  6. 06

    [Submitted on 12 Aug 2026]

    Transport properties in binary neutron star mergers: Effect of magnetic field

    Pranjal Tambe🇮🇳 · Debarati Chatterjee🇮🇳

    In extreme environments such as binary neutron star mergers, temperatures as high as MeV and magnetic fields up to G, reach a regime where neutrino transport governs the macroscopic thermodynamic and chemical evolution. Existing merger simulations rely on zero magnetic field neutrino emissivity and opacity, potentially missing critical transport physics in highly magnetized neutron star cores. We present an exact framework for computing charged current Urca emissivity and neutrino opacity at finite temperature and magnetic field. We employ the Nucleon Width Approximation framework to account for the collisional broadening effects dominant in the high-density core. Our calculations demonstrate that extreme magnetic fields significantly enhance charged current neutrino opacity, effectively reducing the mean free path for thermal neutrinos.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2608.12091 [pdf]
    0 citations
  7. 07

    [Submitted on 12 Aug 2026]

    Quasi-real photons as a probe of exotic nuclei

    Takashi Nakamura · Carlos A. Bertulani

    Coulomb excitation is an inelastic process in which either the target or the projectile is excited by the Coulomb interaction, which can equivalently be described as the absorption of a virtual photon. We discuss Coulomb excitation at relativistic energies, with particular emphasis on Coulomb dissociation, in which an excited projectile subsequently breaks up.

    Comments:
    Invited chapter to the Encyclopedia of Nuclear Physics (Elsevier), 24 pages, 12 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex)
    arXiv:
    2608.12118 [pdf]
    0 citations
  8. 08

    [Submitted on 12 Aug 2026]

    Spatial Entanglement Entropy in Nuclear Fission

    S.C. Li · J.W. Chen · J.C. Pei

    Nuclear fission provides a unique manifestation of spatially nonlocal many-body entanglement. We compute the bipartite spatial entanglement entropy exactly along dynamical fission trajectories, by leveraging the fermionic Gaussian state formulation. Across seven representative fissioning channels, the final entanglement entropy correlates strongly with the intrinsic particle number variance of the fragment, yet exhibits no simple dependence on scission geometries. Most notably the entanglement is significantly suppressed when fragments are magic nuclei, revealing a shell anti-entanglement effect. This work establishes entanglement entropy as a novel lens that extends the conventional conception of nuclear fission.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.12120 [pdf]
    0 citations
  9. 09

    [Submitted on 12 Aug 2026]

    Impact of perturbative tensor interactions on the spontaneous fission half-lives of superheavy nuclei

    R. Rodriguez-Guzman · A. Rakhmankulov · L.M. Robledo · R.N. Bernard

    The standard microscopic description of fission, based on the mean-field Hartree-Fock-Bogoliubov approximation and a semi-classical description of tunneling through the fission barrier, has been used to analyse the impact of introducing a (perturbative) tensor term along with the well known Gogny-D1S force in the spontaneous fission half-lives. Calculations in a series of even-even isotopes of superheavy nuclei ranging from nobelium to darmstatium have been carried out. The results show that the tensor term only impacts the height of the first fission barrier and leaves mostly unaffected the pairing properties and therefore the collective inertias. As a consequence of the reduction in the barrier height, the spontaneous fission lifetimes obtained by including the tensor term are significantly smaller than the ones without it bringing the theoretical predictions in closer agreement with experimental data.

    Comments:
    15 pages, 9 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.12199 [pdf]
    J.Phys.G(2026)·0 citations
  10. 10

    [Submitted on 11 Aug 2026] (cross-list from hep-ph)

    Particle Production, Equilibration, and Quantum Recurrences from Classical Fields

    Iván Cuntín🇪🇸 · Wenyang Qian🇪🇸 · Bin Wu🇪🇸

    We investigate particle production from classical fields, a phenomenon central to the pre-equilibrium dynamics of relativistic heavy-ion collisions and the reheating epoch of the early Universe. Using lattice theory as a proof of principle, we show that this problem is naturally amenable to quantum computation, providing a first-principles framework for nonequilibrium quantum-field dynamics beyond existing approximations. We perform simulations on small spatial lattices, exhausting our available classical computational resources while maintaining a direct mapping to future quantum-computing implementations. We find that particle production is accompanied by equilibration of observables, including the field expectation value, occupation-number distribution, and pressure. The observed equilibration persists for timescales several times longer than the initial equilibration time before the observables resume oscillatory behavior associated with quantum Poincaré recurrences. Our results establish a route toward first-principles studies of equilibration in nonequilibrium quantum field theory and provide insight into the search for the smallest possible locally equilibrated quark-gluon systems at hadron colliders.

    Comments:
    7 pages, 3 figures, plus Supplemental Material
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    2608.11316 [pdf]
    0 citations
  11. 11

    [Submitted on 12 Aug 2026] (cross-list from hep-ph)

    Physics of the Electron-Ion Collider in China

    Bo-Wen Xiao🇨🇳 · Yuxiang Zhao🇨🇳 · Jian Zhou🇨🇳

    The Electron-Ion Collider in China (EicC), a cutting-edge facility under development, aims to unveil the internal structure of nucleons and nuclei by leveraging collisions of high-intensity polarized electrons and ions (polarized protons, polarized deuterons, polarized He, and unpolarized heavy ions up to Uranium) at center-of-mass energies of 15-20 GeV and luminosity of (2-4)cms. Its primary physics objectives include 3D tomography of nucleon spin and momentum structure, fundamental questions regarding the origin of nucleon mass, partonic structure of nuclei and parton interactions with the nuclear environment, and exploration of exotic hadronic states. In this paper, we review the physics potential of the EicC and highlight its unique capabilities for advancing precision nucleon structure studies by combining its specialized kinematic coverage and high luminosity. Since traditional topics like 3D nucleon structure have already been well-covered by several extensive reviews, we have deliberately dedicated significant space to recent progress in nucleon mass decomposition, nucleon energy-energy correlation, quantum information, and artificial intelligence applications in high-energy nuclear physics, which have been emerging rapidly and attracted a tremendous amount of attention in the community.

    Comments:
    93 pages with new updates. Invited review article submitted to "Progress in Particle and Nuclear Physics" (PPNP); comments are welcome; v2
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2608.11712 [pdf]
    PPNP(2026)·1 citation
  12. 12

    [Submitted on 12 Aug 2026] (cross-list from hep-ph)

    Photon emission from rotating plasmas: a generalized McLerran-Toimela formula and the onset of superradiance

    Kirill Tuchin🇺🇸

    The photon emission and absorption spectra of a plasma rotating with constant angular velocity are derived in terms of the spectral function of the current--current correlator. In contrast to the non-rotating case, the leading contribution arises already at one-loop order. The photon emission spectrum and its elliptic flow are calculated for a rotating quark--gluon plasma and compared with the leading two-loop result for a non-rotating plasma. The rotating plasma is found to emit significantly more soft photons than the non-rotating one. An analysis of the emission and absorption of cylindrical waves indicates that photons with energy and azimuthal quantum number satisfying are emitted at a higher rate than they are absorbed, thereby exhibiting the phenomenon of superradiance. It is further argued that these superradiant modes induce an instability of the magnetic field that is generated concurrently with the plasma in relativistic heavy-ion collisions.

    Comments:
    11 pages, 4 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2608.12098 [pdf]
    0 citations
  13. 13

    [Submitted on 12 Aug 2026] (cross-list from nucl-ex)

    Excited states of Nd studied via the NdNd reaction and the observation of possible low-spin two-phonon octupole states at

    A.L. Conley · M. Spieker · R. Aggarwal · L.T. Baby · J. Davis · J. Esparza · I. Hay · B. Kelly · T. Kirk · M.I. Khawaja · R. Mahajan · M. Mestayer and 6 other authors

    We report new data from a NdNd experiment performed at the John D. Fox Accelerator Laboratory of Florida State University. In total, 54 excited states of Nd were observed up to an excitation energy of 3500 keV. In this work, we focus on states and their band members. In contrast to previous work, the band is proposed as the candidate for the two-phonon octupole vibrational band. Supporting IBM-1 calculations are presented. To test the robustness of the IBM calculations, several observables were interrogated and are discussed in this publication. In addition, we make the case that neither the nor the states of the other isotones are likely good candidates for two-phonon octupole states. Based on our new data for Nd, we propose candidates in Sm and Gd. Using available -decay data for states with moderate spins in the yrast sequence and a comparison to IBM calculations, we also show how the staggering of the ratios in the yrast sequence can possibly be used to probe the appearance of bands with multiple octupole phonons.

    Comments:
    10 pages, 9 figures, accepted for publication in Physical Review C
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2608.12101 [pdf]
    PRC(2026)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE