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Nuclear Theory·nucl-th

Thursday·August 20, 2026

13 papers—5 primary·8 cross-listed

All13Primary5Cross-lists8
  1. 01

    [Submitted on 19 Aug 2026]

    Comparison of several model averaging methods in nuclear charge radius predictions

    Huan-Yu Zhang · Rui Jing · Zhen-Hua Zhang · Xin-Hui Wu · Zhong-Ming Niu

    The performance of five model averaging methods, including the arithmetic mean (AM), weighted mean (WM), naive Bayesian model averaging (NBMA), principal component analysis (PCA), and power-moderated mean (PMM) methods, in nuclear charge radius predictions is investigated. Five commonly used nuclear charge radius models are adopted as inputs for the averaging procedures. The charge radius differences between the experimental data and the original nuclear models are analyzed and the results after considering the model averaging methods are also discussed. The calculations show that the NBMA method can provide the best root-mean-square (rms) deviation among these five model averaging methods. The PCA method can extract useful physical information and not only helps to interpret the model differences but also offers a feasible way to construct improved empirical models by recombining the principal components. In contrast to the other methods, whose results worsen upon including a new model with a larger rms deviation, the rms deviation of the PCA method remains almost unaffected. The PMM method is capable of integrating the strengths of various nuclear models and delivering reasonable uncertainty estimates not only in known regions but also in unknown ones. This method can automatically adjust data uncertainties to achieve consistency, and it can provide a tool for a smooth transition of the nuclear charge radius prediction from the WM to the AM. The extrapolation ability of these model averaging methods is checked by 66 newly observed data after year 2021. The calculations show that model averaging offers a reliable strategy for nuclear charge radius predictions, combining high accuracy on known data with robust extrapolation to new measurements. The charge radii and the odd-even staggering in calcium isotopes are also discussed.

    Comments:
    18 pages, 10 figures, 3 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.18463 [pdf]
    0 citations
  2. 02

    [Submitted on 19 Aug 2026]

    Reaction Cross Sections and -Cluster Geometry in C and Be Isotopes

    Tianyu Wu · Baohua Sun · Ulf-G. Meißner · Shihang Shen

    Reaction cross sections are widely used to infer matter radii, yet their sensitivity to nuclear structure beyond radial one-body distributions is less well understood. We combine complete -body nucleon configurations sampled from \textit{ab initio} nuclear lattice effective field theory (NLEFT) with event-by-event Monte Carlo Glauber calculations, thereby retaining the many-body correlations encoded in NLEFT. Using a fixed binary-collision prescription determined by the measured energy- and isospin-dependent total nucleon-nucleon cross sections, the calculations capture the overall magnitudes and energy dependence simultaneously for the available data on C and Be projectiles on carbon and hydrogen. Controlled randomization of angular correlations at fixed matter root-mean-square radius and spherically averaged one-body radial density produces only a weak change in for C but approximately a increase for . The calculations also capture the measured rise--plateau--sharp-rise--reduction trend across Be, a distinctive pattern reflecting the evolution of cluster and halo structures along the isotopic chain. These results show that retains sensitivity to intrinsic many-body geometry beyond a single inferred matter radius, opening a route to studies of exotic -cluster geometries and spatial nucleon correlations through reaction cross sections.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.18538 [pdf]
    0 citations
  3. 03

    [Submitted on 19 Aug 2026]

    Toward testing antinucleonnucleus optical potentials with antineutron scattering lengths

    Hiroyuki Fujioka · Sayaka Ishii

    The antineutronnucleus scattering length is currently known only indirectly, via antiprotonnucleus optical potentials fitted to level shifts and widths of antiprotonic atoms. The antineutronnucleus and antiprotonnucleus potentials are related to each other through charge symmetry. We calculate the scattering length from optical potentials proposed for antiprotonic atoms using nucleon density distributions as input. We find that the scattering length for an nuclide is largely affected by the poorly constrained neutron density distribution and by a possible isovector interaction, one of the mechanisms introduced to reproduce the isotope dependence of antiprotonic data. For , the isovector term modifies the scattering length by () for the real (imaginary) part, an order of magnitude beyond the uncertainty propagated from the isoscalar potential. As no antineutronnucleus scattering data are available below , a direct measurement with recently proposed low-energy antineutron beams would provide the first access to the antinucleonnucleus interaction in the -wave regime.

    Comments:
    12 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2608.18668 [pdf]
    0 citations
  4. 04

    [Submitted on 19 Aug 2026]

    Balancing theory uncertainties in ab initio nuclear structure calculations: Many-body truncation versus finite basis size

    L. Zurek · U. Vernik · P. Demol · T. Duguet · M. Frosini · A. Tichai

    First-principles calculations of atomic nuclei are necessarily incomplete as the Schrödinger equation is solved using approximate methods and due to the finite dimension of the employed Hilbert space. By balancing many-body truncation and basis-size uncertainties, we formalize a criterion for the optimal one-body basis dimension in a given ab initio nuclear structure computation. Next, it is demonstrated that higher-order many-body contributions can be computed using smaller basis sizes than used for the lower orders when a consistent accuracy in the calculation is targeted. Our findings are empirically validated using many-body perturbation theory and coupled-cluster calculations of nuclei spanning a large portion of the nuclear chart using two sets of chiral two- and three-nucleon interactions. The results suggest that considerable computational savings can be obtained using many-body-order-dependent one-body basis sizes.

    Comments:
    16 pages, 12 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2608.18975 [pdf]
    0 citations
  5. 05

    [Submitted on 19 Aug 2026]

    Symmetries of QCD and their relevance for low-energy nuclear physics

    Matthias R. Schindler

    QCD, the theory of the strong interactions, is formulated in terms of quarks and gluons, while low-energy nuclear physics deals with hadrons such as protons, neutrons, and pions. Symmetries establish a systematic connection between these two descriptions of strongly-interacting systems. The objective of this article is to review the symmetries of QCD and to explain how they constrain hadronic interactions. Chiral symmetry, which emerges in QCD in the limit of massless quarks, is of particular importance for low-energy nuclear physics. Together with its explicit and spontaneous breaking, chiral symmetry provides the basis for chiral perturbation theory, the effective field theory describing pions and nucleons at low energies.

    Comments:
    25 pages, 7 figures. Contribution to the Encyclopedia of Nuclear Physics
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2608.18995 [pdf]
    0 citations

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first authorsco-authorsvia INSPIRE