Nuclear Theory·nucl-th

Thu·Sep 17, 2026Thursday·September 17, 2026

8 papers—4 primary·4 cross-listed

01
Learning Nuclear Structure with AI: Radii and Collectivity
Giuliano Giacalone · Sokratis Trifinopoulos · Mike Williams
Low-energy nuclear structure is encoded in a broad body of experimental information across the chart of nuclides. Learning how this information is organized across observables and nuclei can provide a data-driven empirical baseline for theoretical extrapolations and experimental design. Here, we develop held-out ensembles based on NuCLR (Nuclear Co-Learned Representations), a multi-task model of nuclear data, to study charge radii and electric-quadrupole transition strengths. Out-of-fold (OOF) validation shows that shared representation improves performance over single-task learning, yielding a charge-radius $RMS$ deviation of $0.0147 fm$ and a $B (E2)$ $RMS$ deviation of $0.192 e^{2} b^{2}$ across hundreds of nuclides, competitive with state-of-the-art nuclear models. Our error bars estimate the expected prediction accuracy across the nuclear chart, highlighting regions where new data would encode information beyond the learned patterns. NuCLR thus serves as a data-driven surveyor of nuclear structure and a step toward a shared, multi-observable foundation model of the nuclear chart.
nucl-thcs.AIcs.LGnucl-ex
02
Alpha-cluster Formation and Decay: Four-Body Correlation and Configuration Mixing
Yi Wu · Chang Xu
Alpha-decay provides an important probe of nuclear structure and the underlying nucleon-nucleon interaction, while its rigorous microscopic description from first principles remains challenging. For $α$ +magic core systems, a microscopic treatment of $α$ -cluster formation and decay has been achieved by considering both the four-body correlation on top of the core and Pauli blocking. Extending this microscopic description to open-shell nuclei should account for the configuration mixing caused by the residual interactions between valence nucleons near the Fermi surface. In this work, we improve the quartetting wave function approach (QWFA) by incorporating the pairing-induced configuration mixing using the particle-number-projected Bardeen-Cooper-Schrieffer (PBCS) method. We find that the pairing enhance the formation amplitudes of the $α$ -cluster in open-shell nuclei while the closed shells suppress the $α$ -clustering.
nucl-th
03
Sensitivity of the $^{229 m}$ Th clock transition to the fine-structure constant in a Skyrme-Hartree-Fock-BCS approach
Nikolay Minkov · Adriana Pálffy
The sensitivity of the $^{229 m}$ Th isomer transition frequency to the possible temporal variation of the fine-structure constant $α$ is investigated theoretically. We evaluate both the Coulomb as well as the isomer energies in a selfconsistent Hartree-Fock plus Bardeen-Cooper-Schrieffer (BCS) approach with Skyrme energy density functional, taking a detailed account of the nuclear shape deformation and pairing correlations. Our results show that by a fine tuning of the pairing strengths and considering axial octupole deformation, the model can predict a very low isomer energy below the keV limit, which is not accessible in the presence of imposed reflection symmetry. Furthermore, in the model solution with octupole deformation, the difference between the Coulomb energy in the isomeric and ground states is one order of magnitude larger than for the case with imposed reflection symmetry. These results allow for a fully theoretical prediction of the sensitivity of the isomer transition frequency to $α$ in the framework of a microscopic nuclear model, yielding values of $K \sim 1 0^{3} - 1 0^{4}$ , and for a deeper understanding of its underlying physical conditions.
nucl-th
04
From Nuclear Many-Body Correlations to Energy Detector Correlators
João Barata · Giuliano Giacalone
Relativistic nuclear collisions have opened an experimental arena for studying many-body correlations in nuclear ground states. However, the connection between initial-state correlations and final-state multi-particle observables measured at colliders is not yet formulated as a systematically improvable matching problem. We show that detector correlators built from asymptotic energy flows provide a natural framework for realizing such a construction. In particular, we express the asymptotic energy flow as a functional of the early-time stress tensor, and expand it in suitable modes to recover the familiar linear hydrodynamic relations at leading order. Then, motivated by small- $x$ QCD, we map angular projections of detector correlators to multipole-operator correlators computed in the colliding nuclei. We thus establish a systematic formalism for matching long-wavelength correlations between incoming and outgoing QCD states in high-energy hadronic collisions.
nucl-thhep-exhep-phnucl-ex
05
Dark Matter Inelastic Scattering with Nuclei for Direct Detection
Shao-Feng Ge🇨🇳 · Oleg Titov🇨🇳 · Yakun Wang🇨🇳
We investigate the nuclear responses for the WIMP-nucleus scattering in the dark matter direct detection with particular emphasis on the inelastic channel for the $^{129}$ Xe and $^{131}$ Xe isotopes. Our generalization incorporates both the elastic and inelastic scattering channels. With multipole expansion of the effective operators, the angular momentum, parity and time-reversal selection rules can effectively determine the allowed transitions. Instead of the nuclear shell model, we use the state-of-the-art relativistic configuration-interaction density functional theory, which is more suitable for heavy nuclei such as xenon isotopes, to calculate the nuclear response functions. For certain interaction operators, the inelastic contribution can be comparable as its elastic counterpart and some can even dominate by up to three orders of magnitude. Additionally, the higher excited nuclear states can have comparable signal rate as the first excited states. We compare our results with the nuclear shell model calculation. The differences would have significant effects for interpreting the dark matter direct detection searches.
↳ hep-phnucl-th0 citations
06
Constraining the $f_{0} (980)$ Structure and Formation Dynamics via Anisotropy-Response Scaling
Roy A. Lacey
A species-resolved anisotropy-response scaling framework is used to investigate the structure and formation dynamics of the $f_{0} (980)$ in relativistic nuclear collisions. Published measurements in high-multiplicity p+Pb collisions at $s_{N N} = 8.16$ ~TeV exhibit broad scaling closure under a single-meson response construction, with a small effective final-state response, $ζ_{f_{0}} ≃ 0.04$ , whereas a symmetric $K K ˉ$ constituent-response construction gives substantially poorer closure. An explicitly molecular $K K ˉ$ calculation also exhibits single-meson-like scaling but gives a substantially larger effective final-state response, $ζ_{f_{0}} ≃ 0.16$ . Thus, single-meson scaling alone is not a unique structural discriminator. The combined response construction and $ζ_{f_{0}}$ constraints characterize the measured $f_{0} (980)$ by a single-meson-like anisotropy response with weak final-state sensitivity, distinctly different from the molecular benchmark. These results establish anisotropy-response scaling as a new experimental probe of $f_{0} (980)$ formation dynamics and motivate systematic tests across collision systems and beam energies.
↳ nucl-exhep-exnucl-th
07
Nuclear modifications on longitudinal-transverse structure-function ratio $R$ in the deuteron
S. Kumano
In lepton scattering from nuclei, it has been taken for granted that nuclear modifications do not exist for the longitudinal-transverse structure-function ratio $R$ , although nuclear effects in $F_{2}$ have been investigated for a long time. In fact, experimental data of lepton-nucleus scattering have been analyzed with this assumption. It is obviously not appropriate because nuclear modifications exist in the function $R$ theoretically as shown in this work. In this work, we explain nucleon's Fermi motion's effects by using a convolution description for nuclear structure functions, especially on the deuteron. The longitudinal and transverse structure functions are defined by taking the virtual photon momentum direction along the $z$ axis. However, nucleons in a nucleus could move in any direction, so that nucleon's longitudinal and transverse structure functions could mix with each other in the nuclear medium. Such mixing effects could be of the order of $p_{⊥}^{2} / Q^{2}$ , where $p_{⊥}$ is the nucleon's transverse momentum and $Q^{2}$ is given by $Q^{2} = - q^{2}$ with the virtual-photon momentum $q$ , because the transverse Fermi-motion is the source of such a mixture. In addition, nuclear effects are different between the longitudinal and transverse structure functions in the convolution model because their $x$ -dependent functional forms are different. Convolution integrals have different results between the longitudinal and transverse structure functions for nuclei. Because the experiment is in progress at the Thomas Jefferson National Accelerator Facility to measure the function $R$ for the deuteron, the numerical results are shown on the nuclear effects of $R$ in the deuteron. Hopefully, such nuclear effects are found experimentally by future experiments including heavy nuclear targets.
↳ hep-phhep-exhep-latnucl-ex+1
08
Constraints of Big Bang Nucleosynthesis and Cosmological Observations on varying Higgs VEV
Hongrui Feng · Yudong Luo · Toshitaka Kajino · Bao-Hua Sun · Tatsushi Shima
The Higgs vacuum expectation value (VEV) alters both the electroweak and strong interaction rates. We study both effects on Big Bang Nucleosynthesis (BBN) and seek concordance between observed primordial abundances of light elements and cosmological constraints from cosmic microwave background (CMB) fluctuations and anisotropies. We find a strong negative correlation between primordial 4He abundance and the Higgs VEV. Consequently, using a 1.58% uplift of the Higgs VEV during BBN from the current value, an agreement can be achieved among the new primordial 4He abundance, observed by the EMPRESS group, Deuterium abundance determined from absorption lines in the Lyman-alpha forest along the line-of-sight of high-redshift quasars, and the lithium abundance on the Spite plateau. This agreement requires a baryon-to-photon ratio different from the CMB determination, indicating the need for non-standard cosmological evolution between BBN and recombination epochs.We also demonstrate that a 0.2% uplift in the Higgs VEV can partially alleviate the "cosmic Li problem", keeping consistency with the CMB with remaining discrepancy potentially accounted for by stellar depletion mechanisms.
↳ astro-ph.COhep-phnucl-th

Affiliations

first authorsco-authorsvia INSPIRE