PaperPanorama

Nuclear Experiment·nucl-ex

Mon·Aug 10, 2026

7 papers—2 primary·5 cross-listed

All7Primary2Cross-lists5
  1. 01

    The Super Bigbite Spectrometer physics program

    B. Wojtsekhowski🇺🇸 · G. Cates🇺🇸

    The structure of the nucleon is a central problem in strong interaction physics in the non-perturbative regime. Indeed, the vast majority of the known matter in the Universe is made of protons and neutrons which are a remarkable emergent phenomenon of quantum chromodynamics. A critical aspect of investigating nucleon structure experimentally is the measurement of fundamental quantities such the elastic nucleon form factors. Also important is the measurement transverse momentum dependent distribution functions. Accessing such quantities experimentally, however, is challenging because of the small cross sections involved, particularly at high momentum transfer. We present here a physics program that is addressing this challenge based on the Super Bigbite Spectrometer (SBS) that has recently been built at the Thomas Jefferson National Accelerator Facility. SBS provides a relatively large solid angle of 70 msr and can be used at high luminosities and forward-scattering angles. It is based on a single large dipole magnet in an open-geometry in which the detector package has a direct line of sight to the target. This approach is only possible through the use of detector technology that can operate at very high rates while providing excellent spatial resolution. It is the product of solid angle and luminosity that is critical when measuring small cross sections, and in this regard, among spectrometer systems at JLab, SBS is presently unique in its capability. The first set of experiments utilizing SBS has been successfully completed, and more experiments are planned for the future. We also discuss a proposed upgrade that would increase the SBS solid angle to 260 msr, thereby opening perspectives for an even broader physic program.

    nucl-exhep-ex0 citations
  2. 02

    Measurement of the Electron capture of As into the first excited state of Ge

    Hans F. R. Hoffmann🇩🇪 · Björn Lehnert🇩🇪 · Kai Zuber🇩🇪

    The neutrinoless double beta decay of Ge is searched for in the large-scale experiment LEGEND. The measurement of the half-life of this process would give access to the neutrino mass using the nuclear matrix element. Experimentally the contribution of the As ground state to the nuclear matrix element can be investigated via the branching ratios of its and electron capture decay. While energetically, the electron capture of As into the first excited state of Ge is possible and was measured once before this work, the electron capture into the Ge ground state was not observed yet. The present study investigates the branching of As that is produced via As(n,) on a thin AsO sample. A silicon drift detector measures characteristic X-rays emitted by the germanium atoms caused by an inner vacancy after the electron capture. A high-purity germanium detector is used to measure the 562.9keV -rays emitted after electron capture into the excited state. Investigation of coincident signals in both detectors leads to the branching ratio of the As electron capture into the first excited state of Ge of . This is the first measurement with the full uncertainty budget quantified.

    nucl-ex0 citations
  3. 03

    Millisecond-Scale Neural Operator Surrogates for Double-Null Free-Boundary Grad-Shafranov Equilibria

    Plamen G. Krastev

    The Grad-Shafranov (GS) equation governs ideal magnetohydrodynamic equilibrium in tokamak plasmas. Free-boundary GS solvers are central to diverted-equilibrium modeling, but nonlinear Picard iteration introduces computational cost and sample-dependent latency that can become prohibitive in optimization, modeling, and control-oriented loops. Here we train a geometrically conditioned Fourier Neural Operator (FNO) to learn a constrained forward map from spatial coordinates, scalar operating parameters , and prescribed X-point locations to the poloidal-flux field . The model is trained on a controlled family of constrained double-null free-boundary equilibria generated with \textsc{FreeGS} for a single fixed machine geometry and prescribed topology. The best model achieves a mean relative error of , with test error following an empirical power law over . It recovers both X-points to within cm and localizes the O-point to cm. As a physics-consistency diagnostic, the predicted fields satisfy an external finite-difference GS residual evaluation at the same level as the ground-truth fields, with mean normalized residual , indistinguishable from the \textsc{FreeGS} baseline using the same diagnostic. The trained FNO evaluates one equilibrium in ms on GPU and ms on CPU, corresponding to speedups of and relative to \textsc{FreeGS} as configured here, with near-deterministic latency (p95/median ). These results show that neural-operator surrogates can provide accurate, geometrically precise, millisecond-scale equilibrium evaluations for magnetic-confinement fusion workflows within a prescribed topology and machine geometry.

    ↳ physics.plasm-phnucl-exnucl-thphysics.comp-ph0 citations
  4. 04

    Reconstructability and directed flow of short-lived resonances in Au+Au collisions at 19.6 and 200 GeV

    Junyi Han🇨🇳 · Xialei Jiang🇨🇳 · Hongcan Li🇨🇳 · Yaping Wang🇨🇳

    We present a systematic study of the reconstructability and directed flow of hadronic resonances in Au+Au collisions within the UrQMD transport model. The main objective of this work is to investigate how the hadronic stage influences both resonance reconstructability and the final-state directed flow. A set of short-lived hadronic resonances, including , , and , is investigated to quantify their yields and reconstructable fractions as a function of charged-particle multiplicity, characterized by . We compare results at and to investigate possible energy-dependent differences in the reconstructability. Such differences reflect variations in the properties of the hadronic medium. The results are further examined as a function of resonance lifetime, revealing a clear ordering of reconstructability among different resonances. Overall, the reconstructability is found to be primarily governed by resonance lifetime. The directed-flow analysis reveals clear differences between resonances and their corresponding stable hadrons in mid-central collisions, while these differences become significantly weaker in peripheral collisions, highlighting the important role of hadronic evolution in shaping the final-state directed flow. These studies provide a unified picture of how the hadronic stage influences both resonance reconstructability and directed flow, offering new insights into resonance observables in relativistic heavy-ion collisions.

    ↳ nucl-thhep-phnucl-ex0 citations
  5. 05

    Momentum Distributions and Spatial Signatures of Proton Halos in the sd Shell

    Taslima S.C. Diba · Carlos A. Bertulani🇺🇸 · Ronaldo V. Lobato🇧🇷

    We perform a theoretical study of intermediate-energy quasifree one-proton knockout reactions on proton targets. Single-particle wave functions constrained by the experimental proton separation energies are employed to calculate longitudinal momentum distributions, one-proton removal cross sections, and full momentum-space profiles for P, S and Ar nuclei. To establish robust criteria to identify proton halos, the analysis is extended beyond the traditional momentum-width approach by investigating the spatial extension of the valence proton through root-mean-square radii and the probability that the proton resides outside the core nucleus, . We also examine Coulomb-barrier systematics, mirror-nucleus comparisons, realistic spectroscopic mixtures, finite experimental momentum resolution, and uncertainties associated with the proton separation energy. Our calculations indicate that proton-halo structure cannot be identified reliably from a single observable. A consistent interpretation emerges only when momentum distributions, spatial observables, Coulomb effects, and many-body structure are considered simultaneously. Within the present model, P exhibits the strongest proton-halo signatures, while S retains pronounced halo-like features despite its larger Coulomb barrier. The more strongly confined Ar provides a useful comparison and illustrates the progressive suppression of halo observables with increasing binding and core charge.

    ↳ nucl-thnucl-ex0 citations
  6. 06

    Laboratory-frame -matrix and heavy quark drag in the quark-gluon plasma

    Anurag Tiwari🇨🇳 · Min He🇨🇳

    Non-perturbative scattering -matrix is a core input for the evaluation of transport phenomena in a strongly-coupled medium. Existing in-medium -matrix calculations are typically formulated in the two-particle center-of-mass frame, where the scattering equation can be reduced to a lower-dimensional problem. However, a medium explicitly breaks Lorentz invariance and defines a preferred reference frame, entailing that physical observables be constructed from scattering amplitudes evaluated in the medium rest (laboratory) frame. In this work, by exploiting the rotational symmetry about the scattering-pair-momentum axis, we develop a practical framework for solving the in-medium two-body -matrix directly in the laboratory frame while retaining the full dependence on the total pair-momentum and scattering geometry. We demonstrate that the resulting amplitudes differ significantly from conventional center-of-mass-frame results and, when applied to heavy-light quark scattering in the quark-gluon plasma (QGP), lead to 25-40% corrections to heavy-quark drag coefficients at low momenta, thereby removing a significant source of theoretical uncertainty in extracting the QGP transport properties with heavy-quark probes.

    ↳ nucl-thhep-phnucl-ex0 citations
  7. 07

    Charge-state dynamics of barium ions in high-pressure xenon and its implications for Barium-Tagging in searches

    A. Peralta Conde🇨🇷

    Barium tagging (BaTa) is one of the most promising techniques for achieving a nearly background-free search for neutrinoless double-beta decay () in high-pressure xenon time detection chambers. However, the experimental implementation of BaTa depends critically on the chage-state dynamics of the daughter Ba ion produced in the nuclear decay event. In this work, I review the possible recombination channels and evaluate their physical viability. The obtained results indicate that although binary recombination channels are strongly suppressed, three-body recombination assisted by neutral xenon atoms constitutes a physically plausible mechanism for the conversion of Ba into Ba on timescales -milliseconds- comparable to the characteristic detection times in the NEXT experiment. These results suggest that the barium charge state should be regarded as a dynamical quantity with direct implications for the design and experimental implementation of BaTa techniques.

    ↳ physics.atom-phnucl-ex0 citations

Affiliations

first authorsco-authorsvia INSPIRE