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Nuclear Theory·nucl-th

Friday·May 22, 2026

6 papers—4 primary·2 cross-listed

All6Primary4Cross-lists2
  1. 01

    [Submitted on 20 May 2026]

    Uncertainty Quantification of the Ge Neutrinoless Double-Beta Decay Nuclear Matrix Element

    Mihai Horoi🇺🇸 · Andrei Neacsu🇷🇴

    The experimental pursuit of neutrinoless double-beta decay () constitutes one of the most compelling avenues for probing lepton-number violation and exploring physics beyond the Standard Model. Within this landscape, Ge has consistently ranked among the most promising isotopes for current and next-generation bolometric and liquid-scintillator experiments, notably GERDA and LEGEND. In the present work, we adapt a rigorous statistical protocol previously established for Ca~\cite{Horoi-prc22} and Xe~\cite{Horoi-Xe-2023} to the Ge system, utilizing a valence configuration that aligns with our recent investigation of Se~\cite{Neacsu-Symmetry-2024}. Our methodology introduces systematic, bounded fluctuations to the two-body matrix elements of established effective interactions, subsequently monitoring how these perturbations propagate through a suite of low-energy nuclear observables. Special emphasis is placed on the nuclear matrix element (NME), whose theoretical uncertainty currently dominates the interpretation of experimental half-life limits. By integrating these simulated variations into a Bayesian Model Averaging framework and benchmarking against empirical spectroscopic data, we derive a constrained probability distribution for the NME. The resulting analysis yields a central value of 2.46 with an associated standard deviation of 0.25, thereby quantifying the intrinsic theoretical spread within the interacting shell model approach. Furthermore, we perform a comprehensive correlation analysis across all computed observables to evaluate internal consistency, identify non-trivial structural dependencies, and establish benchmarks that may guide the refinement of future effective interactions.

    Comments:
    10 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2605.21657 [pdf]
    3 citations
  2. 02

    [Submitted on 21 May 2026]

    Bootstrapping Two-Nucleon Effective Field Theories

    Q.N. Micha-Mba🇪🇸 · M.S. Sánchez · P.G. Ortega🇪🇸 · J.A. Oller🇪🇸 · D.R. Entem🇪🇸

    Chiral EFT yields singular potentials that require regularization and renormalization when implemented in a dynamical equation such as the Lippmann--Schwinger equation. We employ two different approaches, renormalization with contact terms -- as is most commonly done in chiral EFT -- and the exact N/D method with multiple subtractions. We start with a toy model in which we can control the finite-range expansion of the potential, treating the full potential as the `exact' theory. To assess the statistical consistency of the approaches with the full theory, we use the bootstrap technique. We apply the same framework to study the consistency of chiral EFT at LO and NLO with the Granada phase-shift analysis in the two-nucleon partial wave. Our results show that the NLO potential significantly extends the energy range over which the theory remains valid.

    Comments:
    23 pages, 15 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2605.22134 [pdf]
    0 citations
  3. 03

    [Submitted on 21 May 2026]

    Nuclear Rainbow of Core-Symmetric Systems

    Nguyen Tri Toan Phuc · Nguyen Hoang Phuc · Dao T. Khoa

    The nearside-farside (NF) decomposition method developed originally by Fuller for elastic scattering of a nonidentical nucleus-nucleus system was generalized to study the nuclear rainbow pattern in a symmetric or core-symmetric dinuclear system. It has been shown that the projectile-target identity of an identical system implies a symmetric interchange of the nearside and farside components of elastic scattering amplitude around . A similar interchange appears also in a nonidentical core-symmetric system due to elastic transfer of cluster or nucleon between two identical cores. The analysis of the , , and systems shows how the generalized NF decomposition method reveals the nuclear rainbow pattern in these systems, which can be helpful in probing the real optical potential and nuclear clustering.

    Comments:
    14 pages, 8 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2605.22757 [pdf]
    Few Body Syst.(2026)·0 citations
  4. 04

    [Submitted on 21 May 2026]

    Two bodies left behind

    Raúl A. Briceño🇺🇸 · Caroline S. R. Costa🇺🇸 · Hans-Werner Hammer🇩🇪 · Daniel R. Phillips🇺🇸

    We consider scenarios in which a shallow bound state undergoes breakup by a probe whose energy is high compared to the binding energy. The first two scenarios, which serve as warm-up exercises, involve a single heavy particle bound to a light particle, analogous to a core nucleus bound to a neutron. We show that in quasi-free kinematics, the leading effect comes from the heavy particle being knocked out by the probe, with corrections suppressed by inverse powers of the probe momentum. This formally justifies extracting neutron form factors from high-energy deuteron breakup in quasi-free kinematics. In Scenario 1, the probe is a local current; in Scenario 2, it is hadron scattering. In Scenarios 3 and 4 we consider, respectively, a local current and hadron scattering, but now on a three-body bound state of a heavy particle and two light particles. Hard knockout of the heavy particle leaves two low-energy particles behind, which can interact with one another. In all four scenarios, we prove that the amplitude is dominated by the nearby on-shell pole of the heavy-particle propagator and derive a closed-form expression for this contribution. When two bodies are left behind, the leading amplitude is the product of the scattering of the two light particles, a dynamical function depending on the probe, and a real function related to the bound-state wavefunction. Thus, quasi-free removal of a core nucleus from a system with halo neutrons provides access to on-shell data on multi-neutron interactions. The resulting amplitudes are relativistic and satisfy unitarity for the remnant subsystem exactly. We also provide complementary non-relativistic derivations. While the derivations are for spinless particles, the generalization to spin is straightforward, since the results depend only on quasi-free knockout kinematics; we make no assumptions about the inter-particle dynamics.

    Comments:
    25 pages, 11 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2605.22805 [pdf]
    0 citations
  5. 05

    [Submitted on 21 May 2026] (cross-list from hep-ph)

    Equation of State at High Baryon Densities from a Thermodynamically Informed Neural Network

    Musfer Adzhymambetov🇺🇦

    We present a four-dimensional equation of state for strongly interacting matter at finite temperature and conserved charge densities, constructed using a deep neural network. It is designed for direct use in hybrid models of relativistic heavy-ion collisions: it reproduces hadron resonance gas thermodynamics at typical particlization scales, is consistent with lattice QCD at low baryon chemical potential, and extrapolates into the high-density region inaccessible to either approach, which is precisely the regime targeted by RHIC BES, FAIR, HADES, and CBM. Thermodynamic consistency throughout the full phase space is enforced via a physics-informed loss function. We demonstrate the developed equation of state by implementing it at zero net strangeness and fixed electric-to-baryon charge ratio within the integrated hydrokinetic model.

    Comments:
    Second version. 9 pages, 5 figures. Added link to ready-to-use EoS tables for hydrodynamic simulations. The reader is encouraged to test the equation of state in their hydrodynamic codes and to reach out if help with implementation is needed
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2605.22199 [pdf]
    0 citations
  6. 06

    [Submitted on 21 May 2026] (cross-list from physics.atom-ph)

    Shielded inner-shell transitions in atomic samarium for tests of fundamental physics

    R. Aramyan🇩🇪 · D. Budker🇩🇪 · V. A. Dzuba🇦🇺 · V. V. Flambaum🇦🇺 · S. G. Porsev🇺🇸 · M. S. Safronova🇺🇸 · O. Tretiak🇩🇪 · K. Zhang🇩🇪

    Forbidden atomic transitions provide some of the most stringent low-energy tests of physics beyond the Standard Model, with sensitivity set by the interplay between the sought-for signals and systematics suppressed by symmetry. Here we identify the previously unobserved D level of neutral samarium at , opening the FD inner-shell transition for precision spectroscopy. Candidate lines extracted from dual-comb absorption spectra were assigned using double-resonance population-depletion and sequential-excitation measurements. The observed pressure broadening, , and pressure shift, , indicate an inner-shell -transition shielded from external perturbations. Many-body calculations predict a metastable lifetime (quality factor ), large sensitivity coefficients for variation of the fine-structure constant, and a nuclear-spin-dependent parity-violation amplitude comparable to that of cesium. Crucially, the selection rule suppresses by symmetry both the nuclear-spin-independent parity-violation channel and the M1 and E2 backgrounds that complicated previous heavy-atom experiments, yielding a uniquely clean window onto the nuclear anapole moment. The two stable spin- isotopes of samarium provide a remarkable opportunity to largely cancel atomic-structure uncertainties by measuring the ratio of parity-violation effects in the two isotopes. These results establish neutral samarium as a platform for inner-shell precision spectroscopy and tests of physics beyond the Standard Model.

    Subjects:
    Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th); physics.optics (physics.optics); Quantum Physics (quant-ph)
    arXiv:
    2605.22318 [pdf]
    0 citations

Affiliations

first authorsco-authorsvia INSPIRE