PaperPanorama

Nuclear Experiment·nucl-ex

Thu·Sep 17, 2026

5 papers—1 primary·4 cross-listed

All5Primary1Cross-lists4
  1. 01

    Constraining the 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 in relativistic nuclear collisions. Published measurements in high-multiplicity p+Pb collisions at ~TeV exhibit broad scaling closure under a single-meson response construction, with a small effective final-state response, , whereas a symmetric constituent-response construction gives substantially poorer closure. An explicitly molecular calculation also exhibits single-meson-like scaling but gives a substantially larger effective final-state response, . Thus, single-meson scaling alone is not a unique structural discriminator. The combined response construction and constraints characterize the measured 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 formation dynamics and motivate systematic tests across collision systems and beam energies.

    nucl-exhep-exnucl-th
  2. 02

    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 deviation of and a deviation of 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
  3. 03

    Nuclear modifications on longitudinal-transverse structure-function ratio 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 , although nuclear effects in 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 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 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 , where is the nucleon's transverse momentum and is given by with the virtual-photon momentum , 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 -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 for the deuteron, the numerical results are shown on the nuclear effects of in the deuteron. Hopefully, such nuclear effects are found experimentally by future experiments including heavy nuclear targets.

    ↳ hep-phhep-exhep-latnucl-ex+1
  4. 04

    On the importance of cosmic-ray background in the Atomki anomaly

    Hicham Benmansour · Gianluigi Boca · Gianluca Cavoto · Marco Chiappini · Elia G. Grandoni · Luca Galli · Giovanni Gallucci · Angela Papa · Francesco Renga · Antoine Venturini · Cecilia Voena

    We report Geant4-based simulations of cosmic-ray muon backgrounds in models reproducing the geometries of the five-arm and six-arm e+e- pair spectrometers operated by the Atomki group at Debrecen. Full detector geometries are implemented for both setups, including position-sensitive detectors and plastic scintillators. In both configurations, cosmic muons generating two-arm coincidences produce statistically significant excesses in the opening-angle distribution whose positions are determined by the discrete azimuthal arrangement of detector arms and the plastic scintillators dimensions: in the six-arm spectrometer a peak appears near 140 degrees when the scintillator energy sum is selected in the 8Be transition window (16-20 MeV) and is suppressed for energy-asymmetric pairs, while a distinct peak near 120 degrees emerges in the 4He window (18-22 MeV), with no comparable enhancement in the respective background energy region. These angles, asymmetry dependences, and background characteristics show behaviours similar to those reported by the Atomki group as evidence for a 17 MeV boson. For the five-arm setup, a 140-degree excess is also reproduced at 8Be energies, and normalizing internal pair conversion events and cosmic coincidences to typical Atomki running conditions yields a cosmic-to-IPC ratio above unity in the signal window, indicating that the cosmic background is a leading contribution to the event rate at the energies and angles of interest. While they do not settle the question of the origin of the Atomki excesses, these results highlight the critical importance of a robust cosmic-ray treatment in this type of measurements, and call for a detailed description of the beam-off studies supporting the search for anomalies in the opening-angle vs. energy-sum distribution around the signal region.

    ↳ physics.ins-dethep-exnucl-ex
  5. 05

    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- 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