Nuclear Experiment·nucl-ex

Tue·Sep 1, 2026Tuesday·September 1, 2026

6 papers—1 primary·5 cross-listed

01
Measurement of the $^{3}$ He Spin Structure Functions and Their Moments at Low Q $^{2}$
Jefferson Lab E97-110 · Collaboration
We report measurements of spin-dependent electron scattering from a polarized $^{3}$ He target, $^{3} He (e, e^{'}) X$ , performed at the Thomas Jefferson National Accelerator Facility (Jefferson Lab). The $^{3}$ He spin-dependent virtual-photoabsorption cross sections $σ_{T T}$ and $σ_{L T}$ , or equivalently the spin structure functions $g_{1}$ and $g_{2}$ , and their moments were extracted for $0.032 \leq Q^{2} \leq 0.23$ ~GeV $^{2}$ , with coverage from the two-body breakup threshold through the nucleon-resonance region. The moment $I_{1} (Q^{2})$ reaches a plateau below $Q^{2} ≃ 0.1$ ~GeV $^{2}$ , consistent with the Gerasimov--Drell--Hearn (GDH) expectation, while the moment $I_{T T} (Q^{2})$ , still dominated by the finite-virtuality breakup response, peaks at $Q^{2} ≃ 0.1$ ~GeV $^{2}$ and turns toward the expected GDH value. Together, the two moments constitute the first observation of a nucleus approaching its GDH sum-rule value at the real-photon point. The moments $I_{2} (Q^{2})$ and $I_{L T} (Q^{2})$ yield, respectively, the lowest- $Q^{2}$ nuclear test of the Burkhardt--Cottingham sum rule and the first nuclear test of the Schwinger sum rule. Besides testing fundamental sum rules, these data provide stringent benchmarks for ab initio calculations of the spin structure of light nuclei.
nucl-ex0 citations
02
Torsion and Nonmetricity Constraints From Neutron Spin Rotation in Polarized Matter
Sepehr Samiei🇺🇸 · Ralf Lehnert🇺🇸 · W. Michael Snow🇺🇸
Many modified-gravity frameworks employ non-Riemannian connection degrees of freedom, including torsion and nonmetricity. In Einstein-Cartan-type theories, torsion is associated with spin density, while more general metric-affine frameworks can be investigated through phenomenological searches for in-matter torsion and nonmetricity backgrounds. This work applies an effective field theory approach to characterize general couplings of electron and neutron operators to spacetime torsion and nonmetricity up to mass dimension six, predicting novel neutron-polarization signatures in the presence of an electron background. Neutron spin-rotation data from a polarized-electron ensemble inside a compensated ferrimagnet are used to constrain for the first time axially symmetric, direction-dependent in-matter torsion and nonmetricity combinations.
↳ gr-qchep-exhep-phnucl-ex0 citations
03
Local-nuclear-density dependent calculation of nucleon electromagnetic form factor ratios in finite nuclei
G. Ramalho🇰🇷 · K. Tsushima🇧🇷 · Myung-Ki Cheoun🇰🇷
We calculate the electromagnetic form factors of nucleons bound in finite nuclei and make predictions to the ratio between the electric ( $G_{E}^{*}$ ) and magnetic ( $G_{M}^{*}$ ) form factors in terms of the square of the four-momentum transfer $Q^{2}$ . We extend our previous constant-density calculations within the covariant spectator-QMC framework by incorporating the spatial nuclear density profiles of finite nuclei and quantify the deviations from the average-density approximation used in our previous applications. The impact of the medium effects can then be observed considering the ratio between $G_{E}^{*} / G_{M}^{*}$ and the ratio in free space $G_{E} / G_{M}$ , that define the proton electromagnetic double ratio associated with a given nucleus. The double ratio is expected to remove some systematic uncertainties. There is the expectation that ratios $G_{E}^{*} / G_{M}^{*}$ associated with the bound protons inside the nucleus will be measured in the near future in polarization-transfer experiments $(e A, e^{'} A^{'} p)$ . Anticipating future measurements on the subject, we make predictions for the double ratios, to be compared with the average measurements on the energy states of protons bound to nuclei. We consider the nuclei $^{12}$ C, $^{16}$ O and $^{40}$ Ca. We conclude that the form factors calculated using nuclear density profile function $ρ (r)$ are less suppressed than in the case of the results calculated using the average nuclear density. The results indicate that the relative importance of the low-density surface region increases with $Q^{2}$ , leading to a weaker suppression than that predicted by the average-density approximation. We also make predictions for the ratios associated with neutrons bound to nuclei.
↳ nucl-thhep-exhep-lathep-ph+10 citations
04
Low-energy Muon-Nucleon scattering experiment: LUNE (White Paper)
Chenlei An🇨🇳 · Dong Bai🇨🇳 · Ziyu Bai🇨🇳 · Kai Chen🇨🇳 · Liangwen Chen🇨🇳 · Xiang Chen🇨🇳 · Jianqiao Deng🇨🇳 · Yanxin Dou🇨🇳 · Yicheng Feng🇺🇸 · Zekai Feng · Lu Gao🇨🇳 · Chang Gong🇨🇳 and 61 other authors
The HIAF will provide high-intensity, high-quality muon beams with momenta from 0.5 to 7.5 GeV/c. This energy range is uniquely suited for precision muon scattering, bridging the gap between low-energy electron facilities and future high-energy lepton-ion colliders. In particular, HIAF will enable precision measurements with both positive and negative muon beams over a broad kinematic range, complementing existing electron-scattering facilities such as JLab, EicC and EIC. Based on HIAF muon source, the LUNE Collaboration has been established to address several fundamental questions in nuclear and particle physics, including the proton charge radius puzzle, nucleon electromagnetic structure, and the dynamics of quantum electrodynamics and hadronic interactions. The program proceeds in two phases, from elastic scattering to nucleon structure and beyond-Standard-Model searches. The experiment is expected to determine the proton charge radius with a precision of approximately 1.0\% using elastic muon-proton scattering. It will also perform systematic measurements of the proton electromagnetic form factors with both $μ^{+}$ and $μ^{-}$ beams, enabling precise studies of two-photon exchange effects and stringent tests of quantum electrodynamics. Beyond elastic scattering, LUNE will investigate TMD, gravitational form factors, and nuclear charge radii, providing new insights into the 3D structure of nucleons and nuclei. The experiment will further address important topics including Coulomb-distortion corrections, nuclear medium effects, and possible signatures of physics beyond the Standard Model. This white paper presents the scientific motivation, detector concept, expected performance, and long-term strategy of LUNE.
↳ hep-exnucl-ex0 citations
05
First measurement of the ratio of $ψ (2 S)$ -to- $J / ψ$ inclusive production in $p Ar$ and $pp$ collisions at $s_{NN} = 113 GeV$ with SMOG2
LHCb collaboration: R. Aaij · M. Abdelfatah · A.S.W. Abdelmotteleb · C. Abellan Beteta · F. Abudinén · T. Ackernley · A.A. Adefisoye · B. Adeva · M. Adinolfi · P. Adlarson · C. Agapopoulou · C.A. Aidala and 1179 other authors
A measurement of the $ψ (2 S)$ -to- $J / ψ$ production cross-section ratio is performed in proton-argon ( $p Ar$ ) and proton-proton ( $pp$ ) collisions in fixed-target mode at $s_{NN} = 113 GeV$ . Data samples were collected by the LHCb experiment during argon and hydrogen gas injections in the SMOG2 storage cell, resulting in $p Ar$ and $pp$ collisions, respectively. The $ψ (2 S)$ -to- $J / ψ$ production cross-section ratio is measured as a function of the charmonium transverse momentum, $p_{T}$ , and rapidity in the centre-of-mass system, $y^{*}$ . The $ψ (2 S)$ -to- $J / ψ$ ratio in $p Ar$ collisions over that in $pp$ collisions is measured to be $0.90 \pm 0.04 \pm 0.02$ for $- 2.3 < y^{*} < 0.0$ and $0 < p_{T} < 8 GeV / c$ , indicating the emergence of nuclear effects in the $p Ar$ system. This study acts as a baseline for the interpretation of future measurements with larger systems accessible by the LHCb experiment.
↳ hep-exnucl-ex0 citations
06
Development and characterization of a wingless ICPC HPGe detector with thin amorphous-Ge contacts
S. A. Panamaldeniya🇺🇸 · K. M. Dong🇺🇸 · D. M. Mei🇺🇸
High-purity germanium (HPGe) detectors with thin amorphous-germanium (a-Ge) contacts can provide bipolar charge blocking and surface passivation while minimizing contact-related inactive thickness. We report the fabrication and characterization of a p-type inverted coaxial point-contact (ICPC) HPGe detector using thin a-Ge contacts in a wingless geometry that avoids the protective wing structure used in our previous prototype. The detector was fabricated from a USD-grown, zone-refined HPGe crystal and has a mass of 20.0~g. At 77~K, it exhibited picoampere-scale leakage current and an operational depletion voltage of approximately 440~V. Gamma-ray spectroscopy yielded energy resolutions of 1.75~keV FWHM at 59.5~keV and 3.19~keV FWHM at 662~keV. The calibrated charge-injection method gave an absolute capacitance of 0.496~pF, with an estimated method-level relative uncertainty of 6--8\%, consistent with the 0.488~pF value obtained from electrostatic modeling with \texttt{SolidStateDetectors.jl}. With a $^{241}$ Am source positioned inside the detector bore, the detector showed a source-correlated excess current and a broad degraded-alpha continuum centered near 3558~keV, demonstrating sensitivity to near-surface interactions. Because the source encapsulation, intervening materials, and near-surface charge-collection response were not independently characterized, the continuum is not used to infer a unique dead-layer thickness or energy-loss mechanism. The principal result is successful fabrication and stable sub-pF operation of a 20-g wingless thin-contact ICPC prototype.
↳ physics.ins-dethep-exnucl-ex0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Measurement of the 3He Spin Structure Functions and Their Moments at Low Q2

Torsion and Nonmetricity Constraints From Neutron Spin Rotation in Polarized Matter

Local-nuclear-density dependent calculation of nucleon electromagnetic form factor ratios in finite nuclei

Low-energy Muon-Nucleon scattering experiment: LUNE (White Paper)

First measurement of the ratio of ψ(2S)-to-J/ψ inclusive production in pAr and pp collisions at sNN​​=113GeV with SMOG2

Development and characterization of a wingless ICPC HPGe detector with thin amorphous-Ge contacts

Affiliations

Measurement of the $^{3}$ He Spin Structure Functions and Their Moments at Low Q $^{2}$

First measurement of the ratio of $ψ (2 S)$ -to- $J / ψ$ inclusive production in $p Ar$ and $pp$ collisions at $s_{NN} = 113 GeV$ with SMOG2