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Nuclear Theory·nucl-th

Friday·September 19, 2025

6 papers—4 primary·2 cross-listed

All6Primary4Cross-lists2
  1. 01

    [Submitted on 17 Sept 2025]

    An improved formula for Wigner function and spin polarization in a decoupling relativistic fluid at local thermodynamic equilibrium

    Xin-Li Sheng🇮🇹 · Francesco Becattini🇮🇹 · Daniele Roselli🇮🇹

    We present an upgraded formula for Wigner function and spin polarization of fermions emitted by a relativistic fluid at local thermodynamic equilibrium at the decoupling which improves the one obtained in refs. [1, 2] and used in numerical simulations of relativistic nuclear collisions. By using a new expansion method, applicable to decoupling hypersurfaces with arbitrary geometry, we reproduce the known term proportional to thermal vorticity and obtain an upgraded form of the spin-shear term which captures the dependence on the geometry. The new method also includes additional contributions whose physical nature is to be assessed. The new expression also naturally excludes contributions from space-time gradients in the normal direction of the hypersurface, providing a theoretical justification for the isothermal condition previously imposed a priori. This framework can be extended to particles with arbitrary spin.

    Comments:
    17 pages, 1 figure
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
    arXiv:
    2509.14301 [pdf]
    11 citations
  2. 02

    [Submitted on 18 Sept 2025]

    Secondary bow with ripples in C+C rainbow scattering

    S. Ohkubo · Y. Hirabayashi

    We report, {for the first time, the emergence of} a secondary bow with ripples in C+C nuclear rainbow scattering. This finding was achieved by studying the experimental angular distributions in C+C scattering at incident energies = 240 and 300 MeV, utilizing an extended double-folding model. This model accurately describes all diagonal and off-diagonal coupling potentials derived from the microscopic wave functions for C. Although the observed angular distributions of rainbow scattering at large angles (approaching ) are complicated by the symmetrization of two identical bosonic nuclei, the Airy minimum, associated with a dynamically generated secondary bow with ripples, is clearly identified at approximately 77 for 240 MeV in the fall-off region of the primary nuclear rainbow. This {finding}, along with previous findings in the O+C and C+C systems, {reinforces} the concept of a secondary bow in nuclear rainbow scattering.

    Comments:
    9 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2509.14535 [pdf]
    EPJA(2025)·2 citations
  3. 03

    [Submitted on 18 Sept 2025]

    Systematic Bayesian Evaluation of Resonance Parameters in 19Ne for the 15O(alpha,gamma)19Ne and 18F(p,alpha)15O Reactions

    S.H. Kim · K.Y. Chae · C.H. Kim · C.D. Nesaraja · M.S. Smith

    We present a comprehensive evaluation of the nuclear structure properties of 19Ne using a novel and rigorous Bayesian statistical framework. Precise characterization of 19Ne resonance parameters is critical for accurately determining reaction rates of the astrophysically significant 15O(alpha, gamma)19Ne and 18F(p, alpha)15O reactions, which govern breakout from the hot CNO cycle in X-ray bursts and influence gamma-ray emission in novae, respectively. By reconstructing likelihood functions from published experimental data, including asymmetric uncertainties and upper or lower limits, we derive posterior distributions for resonance energies, decay widths, and branching ratios. Our Bayesian approach systematically incorporates previously reported discrepancies among measurements, providing a statistically robust and consistent treatment of these uncertainties. The evaluated resonance parameters and associated uncertainties provide crucial input for stellar nucleosynthesis modeling, contributing to a refined understanding of explosive astrophysical phenomena.

    Subjects:
    Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
    arXiv:
    2509.14570 [pdf]
    PRC(2025)·1 citation
  4. 04

    [Submitted on 18 Sept 2025]

    Learning Informed Prior Distributions with Normalizing Flows for Bayesian Analysis

    Hendrik Roch · Chun Shen

    We investigate the use of normalizing flow (NF) models as flexible priors in Bayesian inference via Markov Chain Monte Carlo (MCMC) sampling for iterative Bayesian calibration. Trained on posteriors from previous analyses, these models can be used as informative priors that capture non-trivial distributions and correlations in subsequent inference tasks. We compare different training strategies and loss functions, finding that training based on Kullback-Leibler (KL) divergence and unsupervised learning consistently yield the most accurate reproductions of reference distributions. We apply such a sequential Bayesian workflow to a high-energy nuclear physics problem; MCMC with NF-based priors reproduces the results of one-shot joint inference well, provided the target distributions are unimodal. In cases with pronounced multi-modality or dataset tension, distortions may arise, underscoring the need for caution in multi-stage Bayesian inference. A comparison between the pocoMC MCMC sampler and the standard emcee sampler further demonstrates the importance of advanced and robust algorithms for exploring the posterior space. Overall, our results establish NF-based priors as a practical and efficient tool for sequential Bayesian inference in high-dimensional parameter spaces.

    Comments:
    13 pages, 7 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2509.14911 [pdf]
    PRC(2026)·3 citations
  5. 05

    [Submitted on 18 Sept 2025] (cross-list from nucl-ex)

    Refining the deep sub-barrier 12C+12C excitation function with STELLA

    J. Nippert🇫🇷 · S. Courtin🇫🇷 · M. Heine🇫🇷 · D.G. Jenkins🇬🇧 · P. Adsley🇫🇷 · A. Bonhomme🇫🇷 · R. Canavan🇬🇧 · D. Curien🇫🇷 · T. Dumont🇫🇷 · E. Gregor🇫🇷 · G. Harmant🇫🇷 · E. Monpribat🇫🇷 and 18 other authors

    Purpose: We have investigated the cross section around the lowest direct coincident gamma-particle measurements, where previously only limits could be established with the aim of obtaining a detailed description of the excitation function. We have furthermore analysed the ratio of extreme decay branching into the first excited state of daughter nuclei with alpha or proton emission at relative kinetic energies where previous measurements are in disagreement with each other. Conclusions: Our findings in the astrophysics RoI support reaction-rate models with a lower average S-factor trend, that deviates significantly from standard extrapolations between 2.2 MeV and 2.6 MeV, for stellar carbon burning simulations of up to 25 Msol stars. Based on our data, an overall increase of the S-factor at deep subbarrier energy cannot be confirmed. The extremely low ratio of the branching into the first excited state with proton over alpha emission of ~ 2% at 3.23 MeV might indicate the presence of alpha cluster compound states in 24Mg. This highly favours {\alpha} emission with fundamental consequences in possible stellar carbon burning sites.

    Subjects:
    Nuclear Experiment (nucl-ex); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    2509.14717 [pdf]
    PRC(2025)·3 citations
  6. 06

    [Submitted on 18 Sept 2025] (cross-list from hep-ph)

    Melting of heavy quarkonia in QGP using deep neural networks

    Mohammad Yousuf Jamal🇨🇳 · Fu-Peng Li🇨🇳 · Long-Gang Pang🇨🇳 · Guang-You Qin🇨🇳

    Machine learning techniques have emerged as powerful tools for tackling non-perturbative challenges in quantum chromodynamics. In this study, we introduce a data-driven framework employing deep neural networks to systematically predict the temperature-dependent behavior of the screening mass and the strong coupling constant within a quark-gluon plasma medium. These medium-sensitive quantities are subsequently employed to compute the thermal widths and binding energies of heavy quarkonia states, specifically charmonia and bottomonia, by numerically solving the Schrödinger equation with medium-modified heavy quark potentials. To estimate the dissociation temperatures of various quarkonia states, we employ two complementary dissociation criteria: the conventional one, where , and an additional lower bound criterion defined by . This dual-criterion approach provides a more constrained and physically motivated estimate of the temperature range over which quarkonia states dissolve in the QGP environment. Our machine learning-enhanced predictions show excellent agreement with available lattice QCD results, especially for the ground states and , and offer new perspectives on the sequential suppression pattern detected in relativistic heavy-ion collision experiments. Overall, this work advances the quantitative description of quarkonium suppression and demonstrates the prospect of modern machine learning methods to bridge theoretical predictions and experimental observations, thereby contributing significantly to QGP tomography.

    Comments:
    15 pages, 14 figures, 4 tables
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2509.14970 [pdf]
    PRC(2026)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE