Thu·Sep 4, 2025Thursday·September 4, 2025

1. 01*

   Initial results of the TRIUMF ultracold advanced neutron source

   B. Algohi🇨🇦 · D. Anthony🇨🇦 · L. Barrón-Palos🇲🇽 · M. Bossé🇨🇦 · M.P. Bradley🇨🇦 · A. Brossard🇨🇦 · T. Bui🇨🇦 · J. Chak🇨🇦 · R. Chiba🇨🇦 · C. Davis🇨🇦 · R. de Vries🇨🇦 · K. Drury🇨🇦 and 74 other authors

   We report the first results on ultracold neutron production from a new spallation-driven superfluid ${}^4$He (He-II) source at TRIUMF, which is being prepared for a new, precise measurement of the neutron electric dipole moment. A total of $(9.3\pm 0.8)\times 10^5$ ultracold neutrons were observed at a proton beam current of \SI{37}{\uA}, when the target was irradiated for a period of \SI{60}{\s}. The results are in fair agreement with expectations based on a detailed simulation of neutron transport and ultracold neutron source cryogenics. There is some indication that the new source might not be as limited by the conduction of heat through the He-II as originally expected. The results indicate that the source is likely to make its ultimate production goals, once the liquid deuterium cold moderator system is completed, with the expectation that $5.7\times 10^7$~UCNs would be detected in the same experiment with full liquid levels. This would, for example, correspond to delivery of $1.4\times 10^6$~UCNs delivered to each of two nEDM measurement cells, and a statistical uncertainty of $1\times 10^{-27}e$cm on the neutron EDM in 280 days of running.

   nucl-exphysics.ins-detPRC(2026)·3 citations
2. 02*

   Coupling of a Nuclear Transition to a Surface Acoustic Wave

   Albert Nazeeri · Chiara Brandenstein🇺🇸 · Chengjie Jia · Lorenzo Magrini · Giorgio Gratta🇺🇸

   Mechanical modulation of recoilless nuclear transitions allows the dynamic control of $\gamma$-ray emission and absorption. Accessing modulation frequencies well above the nuclear linewidth enables coherent manipulation of the nuclear response. Here we demonstrate high frequency control via efficient coupling a film of enriched ${}^{57}$Fe to a $97.9\mathrm{MHz}$ surface acoustic wave, nearly two orders of magnitude higher than the nuclear linewidth. The mechanical drive produces a comb of absorption sidebands in the Mössbauer spectrum, reflecting the periodic time modulation of the nuclear transitions. This constitutes the highest frequency mechanically driven Mössbauer resonance to date. Our solid-state, monolithic platform establishes a new interface between nuclear transitions and high-frequency acoustics, with applications in $\gamma$-ray quantum optics and precision nuclear spectroscopy.

   ↳ quant-phnucl-exPRL(2026)·2 citations
3. 03*

   Towards Precise Simulations and Inference for the Neutron EDM

   Skyler Degenkolb🇩🇪 · Luigi Favaro🇧🇪 · Peter Fierlinger🇩🇪 · Jennifer Franz🇩🇪 · Husain Manasawala🇩🇪 · Tilman Plehn🇩🇪

   Precision measurements of neutron properties, like its permanent electric dipole moment, rely on understanding complex experimental setups in detail. We show how the properties of stored and transported ultracold neutron ensembles can be simulated reliably. In a second step, we illustrate how they can be used for simulation-based inference of the parameters associated with underlying physics processes such as neutron capture or beta decay. Our proof of principle for simulation-based inference confronts a longstanding challenge with ultracold neutrons: low measurement statistics coupled with a complex apparatus.

   ↳ nucl-thhep-phnucl-ex0 citations
4. 04*

   An experimental setup for the study of gas-cell processes for the S${}^3$-Low Energy Branch

   E. Morin🇫🇷 · W. Dong🇫🇷 · V. Manea🇫🇷 · A. Claessens🇧🇪 · S. Damoy🇫🇷 · R. Ferrer🇧🇪 · S. Franchoo🇫🇷 · S. Geldhof🇫🇷 · T. Hourat🇫🇷 · Yu. Kudryavtsev🇧🇪 · N. Lecesne🇫🇷 · R. Leroy🇫🇷 and 8 other authors

   We present an experimental setup dedicated to the study of in-gas ion processes and characterization of gas stopping cells for the Low Energy Branch of the Super Separator Spectrometer (S${}^3$) at SPIRAL2-GANIL. The first application is the development of a new gas stopper with a neutralization mechanism designed for faster extraction of the radioactive ions. This development should enable in-gas-jet laser spectroscopy and other low-energy experiments with shorter lived radioactive isotopes. We discuss in detail the motivation and objectives of these developments and we present the results of simulations performed in the design phase, as well as the first experimental results.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.B(2026)·1 citation
5. 05*

   A Neural Network Approach to Multi-radionuclide TDCR Beta Spectroscopy

   Li Yi🇨🇳 · Qian Yang🇨🇳

   Liquid scintillation triple-to-doubly coincident ratio (TDCR) spectroscopy is widely adopted as a standard method for radionuclide quantification because of its inherent advantages such as high precision, self-calibrating capability, and independence from radioactive reference sources. However, multiradionuclide analysis via TDCR faces the challenges of limited automation and reliance on mixture-specific standards, which may not be easily available. Here, we present an Artificial Intelligence (AI) framework that combines numerical spectral simulation and deep learning for standard-free automated analysis. $\beta$ spectra for model training were generated using Geant4 simulations coupled with statistically modeled detector response sampling. A tailored neural network architecture, trained on this dataset covering various nuclei mix ratio and quenching scenarios, enables autonomous resolution of individual radionuclide activities and detecting efficiency through end-to-end learning paradigms. The model delivers consistent high accuracy across tasks: activity proportions (mean absolute error = 0.009), detection efficiencies (mean absolute error = 0.002), and spectral reconstruction (Structural Similarity Index = 0.9998), validating its physical plausibility for quenched $\beta$ spectroscopy. This AI-driven methodology exhibits significant potential for automated safety-compliant multiradionuclide analysis with robust generalization, real-time processing capabilities, and engineering feasibility, particularly in scenarios where reference materials are unavailable or rapid field analysis is required.

   ↳ cs.LGcs.AInucl-exphysics.comp-ph+1Nucl.Instrum.Meth.A(2026)·0 citations
6. 06*

   Improved limit on the effective electron neutrino mass with the ECHo-1k experiment

   Fabienne Adam · Felix Ahrens · Luis E. Ardila Perez · Matthias Balzer · Arnulf Barth · Daniel Behrend-Uriarte · Sebastian Berndt · Klaus Blaum · Frederic W. H. Böhm · Martin Braß · Lorenzo Calza · Katerina Chrysalidis and 47 other authors

   The effective electron neutrino mass can be determined by analyzing the endpoint region of the ${}^{163}$Ho electron capture spectrum, provided a measurement with high energy resolution and high statistics using calorimetric techniques. Here, the Electron Capture in ${}^{163}$Ho collaboration, ECHo, presents an analysis of the most precise ${}^{163}$Ho spectrum currently available, obtained with the ECHo-1k experiment and comprising about 200 million events. A very low background rate of $B=9.1(1.3)\times 10^{-6}$ /eV/pixel/day was achieved allowing for a reliable analysis of the endpoint region. The derived endpoint energy $Q=2862(4)$ eV is in excellent agreement with the one independently determined via Penning-trap mass spectrometry of $Q=2863.2(6)$ eV [1]. The upper limit of the effective electron neutrino mass is improved by almost a factor 2 compared to the lowest current value [2], reaching $m_{{\nu }_{\mathrm{e}}}<15$ eV/c${}^2$ (90\% credible interval).

   ↳ hep-exnucl-exPRL(2026)·9 citations
7. 07*

   Probing a Light Scalar Boson with a few-MeV Proton Beam Deep Underground

   Carlo Broggini🇮🇹 · Giuseppe Di Carlo🇮🇹 · Luca Di Luzio🇮🇹 · Denise Piatti🇮🇹 · Claudio Toni🇫🇷

   We propose to investigate the production of a light scalar boson $\varphi$ in low-energy proton-nucleus interactions using the 3.5 MV accelerator of the Bellotti Ion Beam Facility, located in the underground Gran Sasso National Laboratory. Nuclear reactions induced by a few-MeV proton beam on suitable target materials can act as a controlled source of $\varphi$ particles. Owing to the deep-underground location, the facility benefits from substantial cosmic-ray shielding, enabling searches for rare processes with minimal background. The produced $\varphi$ particles will be sought with large-volume, low-background detectors already operating or currently under construction at the Gran Sasso National Laboratory. This approach combines a tunable accelerator-based production mechanism with the exceptional sensitivity of underground rare-event searches, offering a novel avenue to probe light scalar bosons beyond the Standard Model.

   ↳ hep-phhep-exnucl-exPRD(2025)·0 citations
8. 08*

   Particle background characterization and prediction for the NUCLEUS reactor CE$\nu$NS experiment

   H. Abele (1)🇦🇹 · G. Anglogher (2)🇩🇪 · B. Arnold (3)🇦🇹 · M. Atzori Corona (4)🇮🇹 · A. Bento (2)🇩🇪 · E. Bossio (5)🇫🇷 · F. Buchsteiner (3)🇦🇹 · J. Burkhart (3)🇦🇹 · F. Cappella (6)🇮🇹 · M. Cappelli (7, 6)🇮🇹 · N. Casali (6)🇮🇹 · R. Cerulli (4)🇮🇹 and 48 other authors

   NUCLEUS is a cryogenic detection experiment which aims to measure Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS) and to search for new physics at the Chooz nuclear power plant in France. This article reports on the prediction of particle-induced backgrounds, especially focusing on the sub-keV energy range, which is a poorly known region where most of the CE$\nu$NS signal from reactor antineutrinos is expected. Together with measurements of the environmental background radiations at the experimental site, extensive Monte Carlo simulations based on the Geant4 package were run both to optimize the experimental setup for background reduction and to estimate the residual rates arising from different contributions such as cosmic ray-induced radiations, environmental gammas and material radioactivity. The NUCLEUS experimental setup is predicted to achieve a total rejection power of more than two orders of magnitude, leaving a residual background component which is strongly dominated by cosmic ray-induced neutrons. In the CE$\nu$NS signal region of interest between 10 and 100 eV, a total particle background rate of $\sim$ 250 d${}^{-1}$kg${}^{-1}$keV${}^{-1}$ is expected in the CaWO${}_4$ target detectors. This corresponds to a signal-to-background ratio $\gtrsim$ 1, and therefore meets the required specifications in terms of particle background rejection for the detection of reactor antineutrinos through CE$\nu$NS.

   ↳ physics.ins-dethep-exnucl-exEPJC(2026)·6 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.