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Nuclear Theory·nucl-th

Monday·September 15, 2025

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 04

    [Submitted on 11 Sept 2025] (cross-list from nucl-ex)

    Extraction of neutron-capture cross sections on Zr using the charge-exchange Oslo method

    N.D. Pathirana · R.G.T. Zegers · B. Gao · A. Spyrou · A.C. Larsen · H. Berg · D. Bazin · H.L. Crawford · A. Gade · P. Gastis · T. Ginter · C.J. Guess and 7 other authors

    The Nb(,He) reaction at 115 MeV/u was studied to demonstrate that nuclear level densities and -ray strength functions can be extracted from charge-exchange reactions at intermediate energies using the Oslo technique. The matrix of excitation energy in Zr, reconstructed from the (,He) reaction, versus the energy of rays emitted by the excited Zr nuclei, was obtained in an experiment with the S800 Spectrograph operated in coincidence with the GRETINA -ray detector. The extracted level density and -ray strength function obtained by applying the Oslo method to this matrix were used to estimate the Zr(,)Zr cross section by combining the new results with other experimental data and theoretical calculations for 1 and 1 strength functions at higher energies. Good agreement with direct measurements of the Zr(,)Zr cross section was found. The contribution from the upbend in the extracted -ray strength function was important to achieve the consistency as the neutron-capture cross section without this contribution is significantly below the direct measurements otherwise. Since charge-exchange reactions at intermediate energies have long been used for extracting Gamow-Teller strengths, the successful demonstration of the charge-exchange Oslo method enables experiments in which (,) cross sections and Gamow-Teller strengths can be measured simultaneously, which is of benefit for astrophysical studies.

    Subjects:
    Nuclear Experiment (nucl-ex); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    2509.09776 [pdf]
    PRC(2026)·1 citation
  2. 05

    [Submitted on 11 Sept 2025] (cross-list from hep-ph)

    Gluon splitting rates in an anisotropic plasma in the AMY formalism

    Florian Lindenbauer🇦🇹

    We introduce a novel numerical method to obtain the gluon splitting rates in an anisotropic QCD plasma in the AMY formalism, suitable for an anisotropic collision kernel. The method extends previous works by decomposing the additional angular information into Fourier modes, resulting in a significantly larger system of differential equations to solve numerically. It is then tested by calculating the rates for a simple anisotropic model for the collision kernel, which is compared to a thermal system. Remarkably, the obtained rates can be well-approximated by the rates calculated from an angular-averaged collision kernel, while still deviating significantly from equilibrium. An isotropic model for the collision kernel that is commonly used in QCD kinetic theory simulations, and which relies on the infrared temperature and an effective Debye mass, leads to rates that significantly deviate from the nonequilibrium rate, particularly at smaller parton energies.

    Comments:
    12 pages, 3 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2509.09897 [pdf]
    6 citations
  3. 06

    [Submitted on 12 Sept 2025] (cross-list from hep-ph)

    Pseudogauge ambiguity in the distributions of energy density, pressure, and shear force inside the nucleon

    Kenji Fukushima🇯🇵 · Tomoya Uji🇯🇵

    We study the spatial distributions of pressure, energy density, and shear forces inside the nucleon within the two-flavor Skyrme model including vector mesons. This framework has the advantage that nucleon configurations can be stabilized without the Skyrme term. In contrast to the model without vector mesons, however, we realize that the energy-momentum tensor (EMT) becomes pseudo-gauge dependent. We explicitly demonstrate that all these distributions differ between the canonical and Belinfante forms of the EMTs. We identify the pseudo-gauge ambiguity as originating from nonvanishing surface terms associated with spin currents generated by the vector-meson field strength tensors. Furthermore, we show that the pressure and shear-force distributions in the canonical EMT develop singularities at the nucleon center, whereas the corresponding Belinfante distributions remain finite. Finally, we discuss the implications of pseudo-gauge dependence for extracting the confining force and for constructing the equation of state inside the nucleon.

    Comments:
    10 pages, 8 figures. Figures (Fig.2-8) are modified. Qualitative results are unchanged
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2509.10223 [pdf]
    PRD(2026)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE