Tue·Oct 7, 2025Tuesday·October 7, 2025

1. 01*

   Exploring the Origin of Anisotropy in Small Systems: From Symmetric (O+O) to Asymmetric (d+Au) Collisions

   Zhengxi Yan (for the STAR Collaboration)🇺🇸

   This contribution reports STAR measurements of azimuthal anisotropies in produced particle distributions of the d+Au and ${}^{16}$O+${}^{16}$O collisions at $\sqrt{s_{NN}}=200$ GeV, probing the origin of collectivity in small systems. We test the hydrodynamic response of the produced medium by comparing these systems with vastly different initial geometries. The measured elliptic ($v_2$) and triangular ($v_3$) anisotropies, and their event-by-event fluctuations, scale robustly with initial-state eccentricities, consistent with the hydrodynamic behavior expected from a Quark Gluon Plasma (QGP) droplet formed in these collisions. The result also helps constrain the role of sub-nucleon fluctuations in determining the initial conditions. Second, the wide pseudorapidity coverage of the STAR detector is used to investigate longitudinal dynamics. Correlations across different rapidity gaps show no significant impact from flow decorrelation, but non-flow contributions are substantial and require careful subtraction.

   nucl-exEPJ Web Conf.(2026)·1 citation
2. 02*

   Possibility of Inducing ${}^{241}$Am Fluctuations (Primakoff Photon-Magnetic Field Coupling Experiment)

   C. Scarlett🇺🇸 · E. Fischbach🇺🇸 · B. Freeman🇺🇸 · J. J. Coy🇺🇸 · P. Edwards🇺🇸 · D. Osborne🇺🇸 · J. Edwards🇺🇸 · L. Mwibanda🇺🇸 · A. Alsayegh🇺🇸 · M. Chiu🇺🇸

   This paper reports on results from an experiment designed to search for exotic particles interacting with nuclear matter. These particles could be created through the Primakoff coupling between photons and an external magnetic field. Theory suggests this coupling leads to the production of weakly interacting particles (e.g. axions) that are important to understanding the lack of a measured neutron electric dipole moment (nEDM). The current experiment has been run to look for evidence of weakly interacting particles, created by photons propagating through a magnetic field, by studying their influence on the measured decay spectrum of Americium (241Am). The results shown here reflect a statistically significant difference (sigma > 6.0) between observed decays when the experiment was run in a mode that allowed photons to traverse a magnetic field (light mode or sP for system-Photons) when compared to a second mode where the light was blocked from entering the cavity (dark mode or sD for system-Dark). This difference was observed to impact the count rate for the release of a 59.54keV gamma from 237Np. Repeated experimentation suggests the effect is robust and not due to spurious changes in background events. This could be confirmation that the Primakoff mechanism has been observed for visible photons. As importantly, this experiment looks at the possibility to develop a novel nuclear instrument that can modify nuclear decay rates.

   nucl-ex0 citations
3. 03*

   Status of the PrimEx $\eta$ experiment at Jefferson Lab

   Alexander Somov🇺🇸

   The GlueX detector in the experimental Hall $D$ at Jefferson Lab offers a unique opportunity to perform a measurement of the decay width of eta mesons through the Primakoff effect. The PrimEx $\eta$ experiment complements the physics program at Jefferson Lab on measuring the decay width of light pseudoscalar mesons via the Primakoff process. The goal of PrimEx $\eta$ is to measure differential cross sections of $\eta$ mesons at forward angles using a beam of tagged photons incident on a liquid ${}^4\mathrm{He}$ target. The data will be used for the extraction of the decay width. This measurement is vital for understanding fundamental properties like the ratios of the light quark masses and the $\eta$-${\eta }^{\prime }$ mixing angle, and will provide an important test of chiral symmetry breaking in QCD. Our experimental results will help reduce uncertainties on partial widths of all other $\eta$ decays. The experiment collected data during three physics runs between 2019 and 2022. We will give an overview of the PrimEx $\eta$ experiment and the current status of our data analyses. We will also discuss the feasibility of conducting future Primakoff measurements in light of the recent upgrade of the GlueX forward calorimeter and the potential accelerator energy upgrade to 22 GeV.

   nucl-exPoS(2026)·0 citations
4. 04*

   $\beta$-delayed proton pandemonium: A first detailed ${}^{31}$Cl($\beta p\gamma$)${}^{30}$P decay scheme

   Tamas Budner (1 and 2)🇺🇸 · Moshe Friedman (3 and 4)🇺🇸 · Lijie Sun (2 and 5)🇺🇸 · Christopher Wrede (1 and 2)🇺🇸 · B. Alex Brown (1 and 2)🇺🇸 · David Pérez-Loureiro (3)🇺🇸 · Jason Surbrook (1 and 2)🇺🇸 · Alexander Adams (1 and 2)🇺🇸 · Yassid Ayyad (3 and 6)🇪🇸 · Daniel W. Bardayan (7)🇺🇸 · Kyungyuk Chae (8)🇰🇷 · Alan A. Chen (9)🇨🇦 and 11 other authors

   Positron decays of proton-rich nuclides exhibit large $Q$ values, producing complex cascades which frequently involve various radiations, including protons and $\gamma$ rays. Often, only one of the two is measured in a single experiment, limiting the accuracy and completeness of the decay scheme. An example is ${}^{31}$Cl, for which protons and $\gamma$ rays have been measured separately in detail but never with substantial sensitivity to proton-$\gamma$ coincidences. We provide detailed measurements of ${}^{31}$Cl $\beta$-delayed proton decay including $\beta$-$p$-$\gamma$ sequences, extract spectroscopic information on ${}^{31}$S excited states as well as their ${\beta }^{+}$ feedings, and compare to shell-model calculations. A fast fragmented beam of ${}^{31}$Cl provided by the National Superconducting Cyclotron Laboratory (NSCL) was deposited in the Gaseous Detector with Germanium Tagging (GADGET) system. GADGET's gas-filled Proton Detector was used to detect $\beta$-delayed protons, and the Segmented Germanium Array (SeGA) was used to detect $\beta$-delayed $\gamma$ rays. As many as 20 previously unobserved $\beta$-delayed proton transitions are reported, most of which populate excited states of ${}^{30}$P. The first detailed ${}^{31}$Cl($\beta p\gamma$)${}^{30}$P decay scheme is presented, including updated $\beta$-delayed proton energies and intensities, as well as several new ${}^{31}$S levels. Improved agreement is found with theoretical calculations of the Gamow-Teller strengths $B(\text{GT})$ for ${}^{31}$S excitation energies $7.5<E_x<9.5$ MeV. The present work demonstrates that the ability to detect $\beta$-delayed protons and $\gamma$ rays in coincidence is essential for accurate positron decay schemes to compare with nuclear structure theory. This phenomenon for $\beta$-delayed protons resembles the pandemonium effect originally introduced for $\beta$-delayed $\gamma$ rays.

   nucl-exnucl-thPRC(2026)·0 citations
5. 05*

   The challenging first direct measurement of the 65 keV resonance strength in the ${}^{17}$O(p,$\gamma$)${}^{18}$F reaction at LUNA

   D. Piatti · LUNA Collaboration

   A precise determination of the proton capture rates on oxygen is mandatory to predict the abundance ratios of oxygen isotopes in a stellar environment where the hydrogen burning is active. The 17O(p,{\gamma})18F reaction, in particular, plays a crucial role in AGB nucleosynthesis as well as in explosive hydrogen burning occurring in novae and type I supernovae. At the temperature of interest for the former scenario (from 20 MK to 80 MK) the main contribution to the astrophysical reaction rate comes from the Er = 64.5 keV resonance. The strength of this resonance is presently determined only through indirect measurements, with an adopted value {\omega}{\gamma} = 16(3) peV. A new high sensitivity setup has been installed at LUNA, located at Laboratori Nazionali del Gran Sasso. The underground location of LUNA 400kV guarantees a reduction of the cosmic ray background by several orders of magnitude. The residual background was further reduced by a dedicated shielding. On the other hand the 4{\pi}BGO detector efficiency was optimized installing an aluminum target chamber and holder. With about 400 C accumulated on Ta2O5 targets, highly enriched in 17O, the LUNA collaboration has performed the first ever direct measurement of the 64.5 keV resonance strength.

   nucl-exNPA(2025)·0 citations
6. 06*

   Spectral Measurement of the ${}^{214}$Bi beta-decay to the ${}^{214}$Po Ground State with XENONnT

   E. Aprile · J. Aalbers · K. Abe · M. Adrover · S. Ahmed Maouloud · L. Althueser · B. Andrieu · E. Angelino · D. Antón Martin · S. R. Armbruster · F. Arneodo · L. Baudis and 161 other authors

   We report the measurement of the ${}^{214}$Bi beta-decay spectrum to the ground state of ${}^{214}$Po using the XENONnT detector. This decay is classified as first-forbidden non-unique, for which theoretical predictions require detailed nuclear structure modeling. A dedicated identification algorithm isolates a high-purity sample of ground-state beta-decays, explicitly excluding events with associated gamma-rays emission. By comparing the measured spectrum, which covers energies up to 3.27 MeV, with several nuclear models, we find that the prediction based on the conserved vector current (CVC) hypothesis provides the best description of the data. Using this dataset, we additionally derive charge and light yield curves for electronic recoils, extending detector response modeling up to the MeV scale.

   nucl-exhep-exPRC(2026)·4 citations
7. 07*

   Valence $1s-0d$ proton vacancy of the ${}^{32}$Si ground state

   N. Watwood🇺🇸 · C. R. Hoffman🇺🇸 · B. P. Kay🇺🇸 · I. A. Tolstukhin🇺🇸 · J. Chen🇨🇳 · T. L. Tang🇺🇸 · D. Bazin🇺🇸 · Y. Ayyad🇪🇸 · S. Beceiro-Novo🇪🇸 · S. J. Freeman🇬🇧 · L. P. Gaffney🇬🇧 · R. Garg🇺🇸 and 13 other authors

   The ${}^{32}$Si(${}^3$He,$d$)${}^{33}$P reaction was studied in inverse kinematics at 6.3~MeV/$u$. States in ${}^{33}$P corresponding to the proton $1s-0d$ single-particle orbitals were identified up to $\sim$4.5 MeV in excitation energy. The (${}^3$He,$d$) spectroscopic factors were determined from Distorted Wave Born Approximation calculations. When combined with complementary neutron-adding data, the $1s-0d$ proton vacancies in the ${}^{32}$Si ground state were extracted. In conjunction with a re-analysis of data from previous single-particle measurements, the trends in proton and neutron vacancy were explored across the ${}^{28,30,32,34}$Si isotopes. Both proton and neutron vacancy data show gradual changes in their occupancies. The proton $1s_{1/2}$ orbitals in ${}^{32}$Si and ${}^{34}$Si are both consistent with being empty. The ground-state nucleon distributions are described by shell-model calculations constrained to the $1s-0d$ model space.

   nucl-exnucl-thPRC(2025)·2 citations
8. 08*

   Installation and first commissioning results of the JEF lead tungstate calorimeter

   Alexander Somov🇺🇸 · Vladimir Berdnikov🇺🇸

   The Electromagnetic Calorimeter (ECAL), consisting of 1,596 lead tungstate scintillating crystals, has been recently constructed and installed in Experimental Hall D at Jefferson Lab (JLab). The calorimeter is a key component of the JLab Eta Factory Experiment, whose main goal is to measure the decays of eta and eta prime mesons into multi-photon final states. The ECAL replaces the inner part of the former forward lead-glass calorimeter. Scintillation light from each crystal is detected using Hamamatsu R4125 photomultiplier tubes. Calorimeter modules were fabricated and tested in the lab using light from light-emitting diodes before being installed in the detector frame. The detector is currently undergoing commissioning using the light monitoring system and cosmic rays. We will present an overview of the fabrication and testing of the calorimete modules, along with the first detector commissioning results. The ECAL was ready for data-taking in spring 2025.

   ↳ physics.ins-detnucl-exProceedings Volume 13621, Hard X-Ray, Gam…·1 citation
9. 09*

   Next Generation Ta-STJ Sensor Arrays for BSM Physics Searches

   Joseph P.T. Templet🇺🇸 · Spencer Fretwell🇺🇸 · Andrew Marino🇺🇸 · Robin Cantor🇺🇸 · Ad Hall🇺🇸 · Connor Bray🇺🇸 · Caitlyn Stone-Whitehead🇺🇸 · Inwook Kim🇺🇸 · Francisco Ponce🇺🇸 · Wouter Van De Pontseele🇺🇸 · Kyle G. Leach🇺🇸 · Stephan Friedrich🇺🇸

   The Beryllium Electron capture in Superconducting Tunnel junctions (BeEST) experiment uses superconducting tunnel junction (STJ) sensors to search for physics beyond the standard model (BSM) with recoil spectroscopy of the ${}^7$Be EC decay into ${}^7$Li. A pulsed UV laser is used to calibrate the STJs throughout the experiment with $\sim$20 meV precision. Phase-III of the BeEST experiment revealed a systematic calibration discrepancy between STJs. We found these artifacts to be caused by resistive crosstalk and by intensity variations of the calibration laser. For phase-IV of the BeEST experiment, we have removed the crosstalk by designing the STJ array so that each pixel has its own ground wire. We now also use a more stable UV laser for calibration. The new STJ arrays were fabricated at STAR Cryoelectronics and tested at LLNL and FRIB. They have the same high energy resolution of $\sim$1-2~eV in the energy range of interest below 100~eV as before, and they no longer exhibit the earlier calibration artifacts. We discuss the design changes and the STJ array performance for the next phase of the BeEST experiment.

   ↳ physics.ins-detnucl-exquant-phIEEE Trans.Appl.Supercond.(2026)·0 citations
10. 10*

    Flavor, transverse momentum, and azimuthal dependence of charged pion multiplicities in SIDIS with 10.6 GeV electrons

    Hall C SIDIS Collaboration: P. Bosted🇺🇸 · H. Bhatt🇺🇸 · S. Jia🇺🇸 · W. Armstrong🇺🇸 · D. Dutta🇺🇸 · R. Ent🇺🇸 · D. Gaskell🇺🇸 · E. Kinney🇺🇸 · H. Mkrtchyan · S. Ali🇺🇸 · R. Ambrose🇨🇦 · D. Androic🇭🇷 and 58 other authors

    Measurements of SIDIS multiplicities for ${\pi }^{+}$ and ${\pi }^{-}$ from proton and deuteron targets are reported on a grid of hadron kinematic variables $z$, $P_T$, and ${\varphi }^{\ast }$ for leptonic kinematic variables in the range $0.3<x<0.6$ and $3<Q^2<5$ GeV${}^2$. Data were acquired in 2018-2019 at Jefferson Lab Hall C with a 10.6~GeV electron beam impinging on 10-cm-long liquid hydrogen and deuterium targets. Scattered electrons and charged pions were detected in the HMS and SHMS spectrometers, respectively. The multiplicities were fitted for each bin in $(x,Q^2,z,P_t)$ to extract the ${\varphi }^{\ast }$ independent $M_0$ and the azimuthal modulations $⟨\cos ({\varphi }^{\ast })⟩$ and $⟨\cos (2{\varphi }^{\ast })⟩$. The $P_t$-dependence of the $M_0$ results was found to be remarkably consistent for the four cases studied: $ep\to e{\pi }^{+}X$, $ep\to e{\pi }^{-}X$, $ed\to e{\pi }^{+}X$, $ed\to e{\pi }^{-}X$ over the range $0<P_t<0.4$ GeV, as were the multiplicities evaluated near ${\varphi }^{\ast }=180^{\circ }$ over the extended range $0<P_t<0.7$ GeV. The Gaussian widths of the $P_t$-dependence exhibit a quadratic increase with $z$. The $\cos ({\varphi }^{\ast })$ modulations were found to be consistent with zero for ${\pi }^{+}$, in agreement with previous world data, while the ${\pi }^{-}$ moments were, in many cases, significantly greater than zero. The $\cos (2{\varphi }^{\ast })$ modulations were found to be consistent with zero. The higher statistical precision of this dataset compared to previously published data should allow improved determinations of quark transverse momentum distributions and higher twist contributions.

    ↳ hep-exnucl-exPRC(2026)·2 citations
11. 11*

    A Novel, Steerable, Low-Energy Proton Source for Detector Characterization

    Nicholas Macsai🇨🇦 · August Mendelsohn🇨🇦 · David Harrison🇨🇦 · Russell Mammei🇨🇦 · Michael Gericke🇨🇦 · Leah Broussard🇺🇸 · Erick Smith🇺🇸 · Grant Riley🇺🇸 · Glenn Randall🇺🇸 · Mark Makela🇺🇸

    We report on the conversion of the Manitoba II mass spectrometer into a versatile low-energy proton beam facility. This infrastructure is adaptable to any detector-under-test (DUT), and has proven itself effective with the characterization of silicon detectors used in subatomic beyond-the-StandardModel (BSM) searches, namely the Nab experiment. A pencil beam of monoenergetic protons can be produced in a range from 25 keV to 35 keV, achieving a beamcurrent of ~1x10-18 A. Electrostatic steering plates were constructed to direct the Gaussian-profile proton beam over a 117mm diameter areaof-interest with full-width at half-maxima (FWHM) ranging from 0.6 mm to 1.26 mm. This work discusses the modifications and subsequent tests to confirm the beam specifications met the demands of the aforementioned detectors.

    ↳ physics.ins-detnucl-exphysics.acc-phNucl.Instrum.Meth.A(2026)·3 citations
12. 12*

    Lead tungstate calorimeter of the Jefferson Lab Eta Factory experiment

    Alexander Somov🇺🇸

    A new electromagnetic calorimeter (ECAL) consisting of 1596 lead tungstate PbWO${}_4$ scintillating crystals has been fabricated and installed in the experimental Hall D at Jefferson Lab (JLab). The high-granularity, high-resolution calorimeter is required by the JLab Eta Factory experiment, whose main physics goal is to study rare decays of eta mesons. The ECAL replaced the inner part of the forward lead glass calorimeter of the GlueX detector. Signals from the detector will be digitized using twelve-bit flash analog-to-digital converters operated at a sampling rate of 250 MHz. The ECAL is integrated into the trigger system of the GlueX detector using electronics modules designed at JLab. The ECAL is currently at the commissioning stage and should be ready for the physics run in January 2025. We will give an overview of the JEF experiment, the design and construction of the ECAL, and the integration of the detector and its infrastructure into the Hall D experimental setup.

    ↳ physics.ins-detnucl-exEPJ Web Conf.(2025)·7 citations
13. 13*

    SHADES -- ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reaction rate in the Gamow window

    David Rapagnani🇮🇹 · Chemseddine Ananna🇮🇹 · Antonino Di Leva🇮🇹 · Gianluca Imbriani🇮🇹 · Matthias Junker🇮🇹 · Marco Pignatari🇭🇺 · Andreas Best

    Neutron capture reactions are the main contributors to the synthesis of the heavy elements through the s-process. Together with ${}^{13}$C($\alpha$,n)16O, which has recently been measured by the LUNA collaboration in an energy region inside the Gamow peak, 22Ne({\alpha},n)25Mg is the other main neutron source in stars. Its cross section is mostly unknown in the relevant stellar energy (450 keV < Ecm < 750 keV), where only upper limits from direct experiments and highly uncertain estimates from indirect sources exist. The ERC project SHADES (UniNa/INFN) aims to provide for the first time direct cross section data in this region and to reduce the uncertainties of higher energy resonance parameters. High sensitivity measurements will be performed with the new LUNA-MV accelerator at the INFN-LNGS laboratory in Italy: the energy sensitivity of the SHADES hybrid neutron detector, together with the low background environment of the LNGS and the high beam current of the new accelerator promises to improve the sensitivity by over 2 orders of magnitude over the state of the art, allowing to finally probe the unexplored low-energy cross section. Here we present an overview of the project and first results on the setup characterization.

    ↳ physics.ins-detnucl-exEPJ Web Conf.(2022)·3 citations
14. 14*

    Detectors and Shieldings: Past and Future at LUNA

    Chemseddine Ananna🇮🇹 · Lucia Barbieri · Axel Boeltzig🇩🇪 · Matteo Campostrini · Fausto Casaburo🇮🇹 · Alessandro Compagnucci · Laszlo Csedreki · Riccardo Maria Gesue · Jordan Marsh🇬🇧 · Daniela Mercogliano🇮🇹 · Denise Piatti🇮🇹 · Duncan Robb · Ragandeep Singh Sidhu🇩🇪 · Jakub Skowronski🇮🇹

    Nuclear reactions are responsible for the chemical evolution of stars, galaxies and the Universe. Unfortunately, at temperatures of interest for nuclear astrophysics, the cross-sections of the thermonuclear reactions are in the pico-femto-barn range and thus measuring them in the laboratory is extremely challenging. In this framework, major steps forward were made with the advent of underground nuclear astrophysics, pioneered by the Laboratory for Underground Nuclear Astrophysics (LUNA). The cosmic background reduction by several orders of magnitude obtained at LUNA, however, needs to be combined with high-performance detectors and dedicated shieldings to obtain the required sensitivity. In the present paper, we report on the recent and future detector-shielding designs at LUNA.

    ↳ physics.ins-detnucl-exUniverse(2024)·0 citations
15. 15*

    The beam test facility at Jefferson Lab for the precise energy measurement of future calorimeter concepts

    Vladimir V. Berdnikov🇺🇸 · Alexander Somov🇺🇸

    In experimental nuclear physics (NP), high-precision electromagnetic calorimetry typically requires a good energy resolution and linear photosensor response on the level of (1-2)% over a full dynamic range of the detector. The beam of secondary leptons at the Jefferson Lab experimental complex, provided by the Hall D pair spectrometer (PS), is an optimal facility for studies aiming to understand the impact of light collection and signal processing on calorimetry energy resolution under real experimental conditions. The light emission and collection processes depend on radiator component quality and type, while signal processing depends on photosensor type and front-end electronics design. Various calorimeter tower components and detector assemblies for current and future NP experiments were tested within the lepton momentum range of (3-6) GeV/c using PS. The energy resolution of the PS itself is estimated to be better than approximately 0.6%.

    ↳ physics.ins-detnucl-exProceedings Volume 13621, Hard X-Ray, Gam…·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.