Wed·Dec 10, 2025Wednesday·December 10, 2025

1. 01*

   Measurement of the neutron incoherent scattering length of ${}^{199}$Hg using stored ultracold neutrons

   C. Abel🇬🇧 · K. Bodek🇵🇱 · E. Chanel🇨🇭 · P.-J. Chiu🇨🇭 · C.B. Crawford🇺🇸 · M. Daum🇨🇭 · C.B. Doorenbos🇨🇭 · S. Emmenegger🇨🇭 · M. Fertl🇩🇪 · P. Flaux🇫🇷 · A. Fratangelo🇨🇭 · W.C. Griffith🇬🇧 and 26 other authors

   We present the first direct measurement of the neutron incoherent scattering length of ${}^{199}$Hg. The measurement was performed with the Ramsey apparatus of the neutron electric dipole moment experiment located at the Paul Scherrer Institute. The incoherent scattering length $b_{\text{i}}$ was determined by investigating the pseudo-magnetic effect due to the strong interaction between the neutron spins and the nuclear spins of mercury atoms. The resulting frequency shift of the neutron Larmor precession frequency was determined for various ${}^{199}$Hg density and polarization values. The obtained value of $b_{\text{i}}=(-16.2\pm 2.0)$fm agrees in magnitude with previous determinations and provides the so-far unknown sign of the quantity.

   nucl-exhep-ex1 citation
2. 02*

   Pulse Shape Discrimination for Germanium Detectors using Variational Quantum Circuits

   Fabrizio Napolitano🇮🇹

   Pulse shape discrimination (PSD) is a critical component in background rejection for neutrinoless double-beta decay and dark matter searches using Broad Energy Germanium (BEGe) detectors. To date, advanced discrimination has relied on Deep Learning approaches employing e.g. Denoising Autoencoders (DAE) and Convolutional Neural Networks (CNN). While effective, these models require tens of thousands of parameters and heavy pre-processing. In this work, we present, to the best of our knowledge, the first application of Quantum Machine Learning (QML) to real, experimental pulse waveforms from a germanium detector. We propose a quantum-classical hybrid approach using Variational Quantum Circuits (VQC) with amplitude encoding. By mapping the 1024-sample waveforms directly into a 10-qubit Hilbert space, we demonstrate that a VQC with only 302 trainable parameters achieves a receiver operating characteristic (ROC) area under the curve (AUC) of 0.98 and a global accuracy of 97.1%. This result demonstrates that even in the current Noisy Intermediate-Scale Quantum (NISQ) era, quantum models can match the performance of state-of-the-art classical baselines while reducing model complexity by over two orders of magnitude. Furthermore, we envision a scenario where future quantum sensors transmit quantum states directly to such processing units, exploiting the exponentially large Hilbert space in a natively quantum pipeline.

   ↳ physics.ins-dethep-exnucl-ex0 citations
3. 03*

   $J/\psi$-Meson Nucleon Scattering Length from Threshold Photoproduction on Light Nuclei

   Igor I. Strakovsky (GWU)🇺🇸 · William J. Briscoe (GWU)🇺🇸 · Philipp Gubler (JAEA)🇯🇵 · Jackson R. Pybus (LANL)🇺🇸 · Axel Schmidt (GWU)🇺🇸 · Alexander Somov (JLab)🇺🇸

   The quality of recent SRC/CT Collaboration $J/\psi$ photoproduction data off a ${}^4$He target from Hall~D at Jefferson Laboratory, combined with the feasibility of measuring the reaction close to the free-nucleon energy threshold, opens the door to using incoherent $J/\psi$ photoproduction to access a variety of interesting physics aspects. An example is an estimate of the $J/\psi p$ scattering length $|{\alpha }_{J/\psi p}|$ on the bound proton obtained using the Vector Meson Dominance model. This value can be compared with that of the free proton from the GlueX Collaboration. One may then project what would be expected from the SRC/CT Collaboration Experiment E12--25--002, which was recently approved by the JLab PAC. Using a plane-wave theoretical model to generate quasi-data, we find the experiment could achieve a result of $|{\alpha }_{J/\psi p}|=3.08\pm 0.45\mathrm{mfm}$, an uncertainty competitive with that of the free-proton measurement. A comparison between the two would allow an evaluation of the effects of medium modification in the case of light nuclei.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2026)·4 citations
4. 04*

   Toward an usage of americium-241 for filter calibration

   G. Dougniaux (Asnr, Asnr/Psn-Res/Sca/Lpma) · B. Sabot (Lnhb (Cea, List)) · S. Pierre (Lnhb (Cea, List)) · B. Dhieux Lestavel (Asnr, Asnr/Psn-Res/Sca/Lpma)

   In nuclear safety and environmental studies, it is necessary to measure the activity of aerosols collected on filters. The calibration of these filters' measurement chains currently involves producing a reference filter with a controlled deposit of aerosol marked by a specific radionuclide. In France, commonly used radionuclides include 137 Cs for gamma or beta emitters, 90 Sr/ 90 Y for beta emitters, and 239 Pu for alpha emitters. However, using 239 Pu presents several issues, notably the destruction of the filter required to determine its traceable activity and the associated uncertainties. The challenge of this project is to propose a radionuclide enabling non-destructive, SI-traceable measurement while retaining the reference filter. The proposed radionuclide is 241 Am, which is both alpha and gamma-emitting and allows for precise non-destructive measurements. Reference filters are produced on the IRSN's ICARE test bench with calibrated aerosols tagged with 241 Am. The reference activity of theses filters is measured by gamma spectrometry on CEA/LNHB reference counter. A series of tests confirmed that 241 Am provides accurate activity determination with minimal uncertainty. Consequently, adopting 241 Am can significantly improve the reliability of radioactive contamination monitoring while avoiding practical challenges associated with plutonium.

   ↳ physics.ins-detnucl-exRadioprotection(2025)·0 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.