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PTOLEMY Collaboration(Ammendola, R. et al), & Gariazzo, S. (2026). Ultra-high precision high voltage system for PTOLEMY. J. Instrum., 21(4), P04009–19pp.
Abstract: The PTOLEMY project is prototyping a novel electromagnetic filter for high-precision β spectroscopy, with the ultimate and ambitious long-term goal of detecting the cosmic neutrino background through electron capture on tritium bound to graphene. Intermediate small-scale prototypes can achieve competitive sensitivity to the effective neutrino mass, even with reduced energy resolution. To reach an energy resolution better than 500 meV at the tritium β-spectrum endpoint of 18.6 keV, and accounting for all uncertainties in the filtering chain, the electrode voltage must be controlled at the level of a few parts per million and monitored in real time. In this work, we present the first results obtained in this effort, using a chain of commercial ultra-high-precision voltage references, read out by precision multimeters and afield mill device. The currently available precision on high voltage is, in the conservative case, as low as 0.2 ppm per 1 kV single board and less than or similar to 50 mV over the 10 kV series, presently limited by field mill read-out noise. However, assuming uncor related Gaussian noise extrapolation, the real precision could in principle be as low as 0.05 ppm over 20 kV.
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DUNE Collaboration(Abbaslu, S. et al), Amar Es-Sghir, H., Amedo, P., Barenboim, G., Benitez Montiel, C., Capo, J., et al. (2026). Operation of a Modular 3D-Pixelated Liquid Argon Time-Projection Chamber in a Neutrino Beam. Instrum., 10(1), 18–33pp.
Abstract: The 2x2 Demonstrator, a prototype for the Deep Underground Neutrino Experiment (DUNE) liquid argon (LAr) Near Detector, was exposed to the Neutrinos from the Main Injector (NuMI) neutrino beam at Fermi National Accelerator Laboratory (Fermilab). This detector is a prototype of a new modular design for a liquid argon time-projection chamber (LArTPC), comprising a two-by-two array of four modules, each further segmented into two optically isolated LArTPCs. The 2x2 Demonstrator features a number of pioneering technologies, including a low-profile resistive field shell to establish drift fields, native 3D ionization pixelated imaging, and a high-coverage dielectric light readout system. The 2.4-tonne active mass detector is flanked upstream and downstream by supplemental solid-scintillator tracking planes, repurposed from the MINERvA experiment, which track ionizing particles exiting the argon volume. The antineutrino beam data collected by the detector over a 4.5 day period in 2024 include over 30,000 neutrino interactions in the LAr active volume-the first neutrino interactions reported by a DUNE detector prototype. During its physics-quality run, the 2x2 Demonstrator operated at a nominal drift field of 500 V/cm and maintained good LAr purity, with a stable electron lifetime of approximately 1.25 ms. This paper describes the detector and supporting systems, summarizes the installation and commissioning, and presents the initial validation of collected NuMI beam and off-beam self-triggers. In addition, it highlights observed interactions in the detector volume, including candidate muon antineutrino events.
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Escudeiro, R. et al, Perez-Vidal, R. M., Algora, A., Deltoro, J. M., Gadea, A., Jurado, M., et al. (2026). Anomalous quadrupole transition probabilities in the f7/2 mirror nuclei. Physical Review C, 113(4), 044304.
Abstract: Lifetimes of several excited states in the mirror nuclei 47Cr – 47V and 49Mn – 49Cr, located at the center of the f7/2 shell, were measured using the advanced gamma -ray tracking array AGATA. The Doppler shift attenuation method was employed to determine such lifetimes in the subpicosecond range. The reduced transition probabilities obtained from the lifetimes are compared to shell-model calculations in the full f p space. The shell-model-calculated B(E2) values were underestimated in comparison with experimental data. In particular, large discrepancies are obtained in 49Mn at low spin. These results suggest an incomplete understanding of low-energy states in the studied nuclei and call for further refinement of the existing nuclear structure theories.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2026). Search for heavy neutral leptons in decays of W bosons produced in 13 TeV pp collisions using prompt signatures in the ATLAS detector. European Physical Journal C, 86(2), 153.
Abstract: The existence of right-handed neutrinos with Majorana masses below the electroweak scale could help address the origins of neutrino masses, the matter-antimatter asymmetry, and dark matter. In this paper, leptonic decays of W bosons from 140 fb(-1) of 13 TeV proton-proton collisions at the LHC, reconstructed in the ATLAS experiment, are used to search for heavy neutral leptons produced through their mixing with muon or electron neutrinos in a scenario with lepton number violation. The search is conducted using prompt leptonic decay signatures. The considered final states require two same-charge leptons or three leptons, while vetoing three-lepton same-flavour topologies. No significant excess over the expected Standard Model backgrounds is found, leading to constraints on the heavy neutral lepton's mixing with muon and electron neutrinos for heavy-neutral-lepton masses. The analysis excludes vertical bar U-e vertical bar(2) values above 8x10(-5) and vertical bar U-mu vertical bar(2) values above 5.0x10(-5) in the full mass range of 8-65 GeV. The strongest constraints are placed on heavy-neutral-lepton masses in the range 15-30 GeV of vertical bar U-e vertical bar(2) < 1.1 x 10(-5) and vertical bar U-mu vertical bar(2) < 5 x 10(-6).
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Wimmer, K. et al, & Huyuk, T. (2026). Precision tests of isospin symmetry through Coulomb excitation of A=62 nuclei. Phys. Lett. B, 876, 140391–6pp.
Abstract: Isospin symmetry in the A = 62 mass system was investigated through Coulomb excitation reactions at the RIKEN Radioactive Isotope Beam Factory. Beams of 62Zn, 62Ga, and 62Ge were studied using the BigRIPS-ZeroDegree-DALI2+ setup under identical experimental conditions, allowing for cancellation of systematic uncertainties. Inelastic scattering cross sections measured with two different targets were used to extract nuclear deformation lengths and E2 matrix elements. The isospin symmetry of the A = 62 system was rigorously tested by examining the linearity of the proton matrix elements within the triplet with high precision. The observed linear relationship between the reduced proton matrix elements for the three nuclei holds within experimental uncertainties, providing a stringent test of isospin symmetry. This experiment provides the most accurate test, to date, of isospin symmetry rules using transition matrix elements. These results were interpreted using large-scale shell-model calculations, offering valuable insights into isospin symmetry behavior in this region of the nuclear chart.
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