Nuclear Theory·nucl-th

Friday·July 17, 2026

15 papers—8 primary·7 cross-listed

01
[Submitted on 15 Jul 2026]
Exploring the shell structure of trapped superfluid gases
G. Palkanoglou · R. Curry · S. Gandolfi
We provide quantum Monte Carlo calculations of a two-component Fermi system interacting with an attractive interaction confined in harmonic traps. We investigate the role of the interaction's scattering length and effective range and show its important role in modifying shell effects in the structure of these systems. We show that in the strongly interacting regime, where the scattering length is large, the dominant role to shell effects is due to the effective range. These conclusions are very relevant for nuclear physics, in particular for neutron-rich systems, and open the way to perform new atomic experiments that can help to explain the disappearance of shell-effects in nuclei.
Comments:
9 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas)
arXiv:
2607.14214 [pdf]
0 citations
02
[Submitted on 15 Jul 2026]
Bayesian Inference for Extracting Barrier Distributions from Fusion Excitation Functions
Aaron Philip · Pablo Giuliani · Kyle Godbey
Barrier distributions encode rich information about the structure and dynamics of fusing nuclei, but extracting them from experimental fusion cross sections requires an estimate of the fusion excitation function's second derivative. In this work we approach the task of extracting barrier distributions with uncertainty estimates from sparse experimental measurements as a Bayesian inference problem. We introduce a method based on AutoBNN, an interpretable Bayesian machine learning framework, to provide a robust statistical approach for analyzing fusion excitation functions. Benchmarking against Gaussian process regression on simulated excitation functions that span a wide range of realistic experimental conditions, we find that AutoBNN more faithfully recovers the underlying barrier distribution and reports well-calibrated uncertainties. We then apply the AutoBNN method to four experimentally measured heavy-ion fusion reactions where it mitigates spurious above-barrier structure and constrains existing predictions. Alongside these results, we have developed a user-friendly software implementation of our method, facilitating its application to future heavy and light-ion fusion experiments.
Comments:
9 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2607.14422 [pdf]
0 citations
03
[Submitted on 16 Jul 2026]
Impact of tensor-rank components of chiral three-nucleon forces on the single-particle structure of calcium isotopes
Tokuro Fukui · Giovanni De Gregorio · Angela Gargano · Chi Zhang · Furong Xu
Background: Chiral three-nucleon forces (3NFs) play a key role in the microscopic description of nuclear shell evolution. A recent work introduced an irreducible tensor decomposition of the chiral 3NF at next-to-next-to-leading order and showed that, in $p$ -shell nuclei, the enhancement of the $0 p_{3/2}$ -- $0 p_{1/2}$ spin--orbit (SO) splitting is mainly driven by its rank-1 component. Purpose: We extend the aforementioned analysis to the $0 f 1 p$ shell to investigate whether the same mechanism persists in a heavier valence space, and how the different tensor-rank components of the 3NF affect structure properties of calcium isotopes. Methods: Effective shell-model Hamiltonians for neutrons outside the doubly magic $^{40}$ Ca core are derived from chiral two-nucleon force plus 3NF. The latter is progressively included through its rank- $λ$ components ( $λ = 0, 1, 2, 3$ ), allowing us to isolate their impact on the evolution of the neutron single-particle structure. Results: The significant enhancement of the SO splittings for both $1 p$ and $0 f$ orbitals produced by the chiral 3NF is mainly induced by its rank-1 component. The rank-2 term gives a smaller contribution, while the rank-3 term is negligible. The rank-0 component, and to a lesser extent the rank-1 component, are found to play an important role in determining the spacings between orbitals with different orbital angular momenta. All modifications induced by the 3NF in the single-particle structure have a relevant impact on the shell-closure properties of $^{48}$ Ca. Conclusions: The dominance of the rank-1 two-pion-exchange component of the 3NF in explaining the enhancement of SO splitting -- previously identified in the $p$ shell -- persists in the $0 f 1 p$ shell. Observed effects of the 3NF related to the different angular-momentum dependence of the orbitals are shown to arise essentially from their rank-0 and rank-1 components.
Comments:
9 pages, 5 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2607.14458 [pdf]
0 citations
04
[Submitted on 16 Jul 2026]
Universal Properties of Near-Threshold Single-Neutron Resonances
Myungkuk Kim · Young-Ho Song · Hans-Werner Hammer · Youngman Kim · Dean Lee · Yuan-Zhuo Ma
We establish universal width predictions for near-threshold single-neutron resonances in $L > 0$ partial waves. Our results go beyond Wigner's well-known scaling behavior of cross sections near threshold. We show that the finite square-well potential exhibits discrete scale invariance at zero energy. From this fact, we derive an analytic baseline for the resonance width that depends only on geometry, angular momentum, and resonance energy, and not on internal short-distance nuclear details or radial excitation. This is a nontrivial property that is unique to the finite square-well potential and does not occur for other potentials. Application to observed p-wave and d-wave resonances demonstrates that the square-well result provides a robust baseline. We show that discrete scale invariance erases radial-node information in the sharp-boundary limit, but realistic Woods-Saxon diffuseness breaks this invariance, suppressing the reduced width by a factor sensitive to the internal radial excitation. These results provide a simple geometric benchmark for identifying when observed neutron resonances are controlled by universal threshold physics and when they exhibit systematic deviations driven by structure-dependent effects.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2607.14464 [pdf]
0 citations
05
[Submitted on 16 Jul 2026]
On the Bohr-Sommerfeld quantization condition and assault frequency in a semiclassical model for {\alpha} decay
Le Hoang Chien · Nguyen Tri Toan Phuc
We study the impacts of the Bohr-Sommerfeld quantization condition and the assault frequency on the {\alpha} decay half-life within the semiclassical model. The potential between the {\alpha} particle and daughter nucleus is calculated by the double-folding model using the CDM3Y3 density-dependent nucleon-nucleon interaction with a finite-range exchange term. We show that the proper implementation of the Bohr-Sommerfeld condition leads to a considerable change of the calculated {\alpha} decay half-life with certain forms of potential. We also propose an alternative treatment for the assault frequency based on the generalized oscillator potential. This description of assault frequency considerably improves the agreement between the calculated {\alpha} decay half-lives and the experimental data.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.14540 [pdf]
NPA(2022)·5 citations
06
[Submitted on 16 Jul 2026]
Toponium Spectrum in the Complex-Energy Plane
Zhanduo Tang🇺🇸 · Oliver Fast🇺🇸 · Ralf Rapp🇺🇸
The electroweak decay width of the top quark of ~2 GeV is comparable to binding energies expected for the toponium system, raising the long-standing question of whether top and antitop quarks can sustain meaningful bound states. This issue has been been reignited by recent discoveries of a cross section enhancement near the t-tbar threshold by the CMS and ATLAS collaborations in pp collisions at the LHC. Here, we deploy a T-matrix approach with an underlying Cornell potential to study the properties of the toponium system by varying the top-quark widths in the intermediate propagators. In particular, we carry out a complex-energy analysis of the T-matrix to assess how its poles, as a rigorous criterion for bound-state formation, develop from the limit of small widths to realistic ones. We also revisit the impact of the confining force in the potential on the toponium T-matrix.
Comments:
5 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.14554 [pdf]
0 citations
07
[Submitted on 16 Jul 2026]
Responses of multiparticle observables to multidimensional nuclear deformation in relativistic heavy-ion collisions
Ying Shan Zhao🇨🇳 · Yifeng Sun🇨🇳
Relativistic heavy-ion collisions provide a unique opportunity to probe ground-state nuclear structure through its imprint on the initial collision geometry. We investigate how multiparticle observables respond to combined variations of quadrupole deformation, triaxiality, and hexadecapole deformation, using $^{129}$ Xe+ $^{129}$ Xe collisions as a representative testing ground. We perform a joint analysis in the three-dimensional $(β_{2}, γ, β_{4})$ parameter space and construct initial-state estimators for several flow and mean transverse momentum correlation observables. At the initial-state level, $ρ_{2}$ is primarily sensitive to $β_{2}$ and $γ$ , with its sensitivity to $γ$ enhanced at nonzero $β_{2}$ . The nonlinear response coefficient $χ_{4, 22}$ is predominantly sensitive to $β_{4}$ , while its dependence on $β_{2}$ and $γ$ remains comparatively weak. Higher-order correlators exhibit more complex multidimensional response patterns; in particular, $ρ_{224}$ shows a dependence on $γ$ and $β_{4}$ that becomes more pronounced at finite $β_{2}$ . We further employ the iEBE-VISHNU hybrid model to examine whether these deformation sensitivities survive the subsequent dynamical evolution. The final-state calculations indicate that the sensitivity of $ρ_{2}$ to $β_{2}$ and $γ$ is largely preserved, whereas the $β_{4}$ sensitivity of $χ_{4, 22}$ is substantially reduced. For the other higher-order observables, the initial-state sensitivities are modified by the evolution or cannot be resolved with the present statistics.
Comments:
11 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.14776 [pdf]
0 citations
08
[Submitted on 16 Jul 2026]
Extracting nuclear charge radii from binding energies: a single-parameter empirical formula with structural corrections
Pengfei Ma · Minghui Hu · Kai Ren · Junlong Tian · Cheng Li
Nuclear binding energies and charge radii stem from the same underlying physics: saturation, isospin dependence, shell structure, and deformation. Binding-energy data therefore provide a natural constraint for charge-radius modeling. We propose a one-parameter charge-radius formula ( $BECR_{1p}$ ) that combines binding-energy correlations with local structural corrections. On a curated set of 893 experimental charge radii, the macroscopic BECR term alone reproduces the leading charge-radius scale with a root-mean-square deviation (RMSD) of 0.0345 fm; adding shell, odd--even, finite-size, and deformation corrections further reduces the RMSD of BECR1p to 0.0138 fm. An anisotropic kernel ridge regression (AKRR) applied to the residuals further lowers the leave-one-out cross-validation RMSD to about 0.0081 fm. We use the formula to predict charge radii for 11205 nuclei across the nuclear chart.
Comments:
15 pages, 5 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.15064 [pdf]
1 citation

Affiliations

first authorsco-authorsvia INSPIRE