Belle II VTX Collaboration(Babeluk, M. et al)., Marinas, C., & Mazorra de Cos, J. (2024). The DMAPS upgrade of the Belle II vertex detector. Nucl. Instrum. Methods Phys. Res. A, 1064, 169428–5pp.
Abstract: The Belle II experiment at KEK in Japan considers an upgrade for the vertex detector system in line with the accelerator upgrade for higher luminosity at long shutdown 2 planned for 2028. One proposal for the upgrade of the vertex detector called VTX aims to improve background robustness and reduce occupancy using small and fast pixels. VTX accommodates the OBELIX depleted monolithic active CMOS pixel sensor (DMAPS) on all five proposed layers. OBELIX is specifically developed for the VTX application and based on the TJ-Monopix2 chip initially developed to meet the requirements of the outer layers of the ATLAS inner tracker (ITk). This paper will review recent tests of the TJ-Monopix2 chip as well as various design aspects of the OBELIX-1 chip currently under development.
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Lerendegui-Marco, J., Babiano-Suarez, V., Domingo-Pardo, C., Ladarescu, I., Tarifeno-Saldivia, A., & de la Fuente-Rosales, G. (2024). Pushing the high count rate limits of scintillation detectors for challenging neutron-capture experiments. Nucl. Instrum. Methods Phys. Res. A, 1064, 169385–13pp.
Abstract: One of the critical aspects for the accurate determination of neutron capture cross sections when combining time-of-flight and total energy detector techniques is the characterization and control of systematic uncertainties associated to the measuring devices. In this work we explore the most conspicuous effects associated to harsh count rate conditions: dead-time and pile-up effects. Both effects, when not properly treated, can lead to large systematic uncertainties and bias in the determination of neutron cross sections. In the majority of neutron capture measurements carried out at the CERN nTOF facility, the detectors of choice are the C6D6 liquid-based either in form of large-volume cells or recently commissioned sTED detector array, consisting of much smaller-volume modules. To account for the aforementioned effects, we introduce a Monte Carlo model for these detectors mimicking harsh count rate conditions similar to those happening at the CERN nTOF 20 m flight path vertical measuring station. The model parameters are extracted by comparison with the experimental data taken at the same facility during 2022 experimental campaign. We propose a novel methodology to consider both, dead-time and pile-up effects simultaneously for these fast detectors and check the applicability to experimental data from Au-197(n, gamma), including the saturated 4.9 eV resonance which is an important component of normalization for neutron cross section measurements.
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R3B Collaboration(Benlliure, J. et al), Cortina-Gil, D., & Nacher, E. (2025). Fission studies using quasi-free NN scattering reactions in inverse kinematics. Nucl. Phys. A, 1063, 123173–5pp.
Abstract: The combined use of the inverse kinematics technique and the advanced detection setup R3B (Reactions with Relativistic Radioactive Beams) at GSI/FAIR provides unique opportunities to study the fission process. This approach provides access to the complete isotopic identification of the two fission fragments, the precise determination of their velocities and the measurement of the neutrons and gammas emitted in coincidence, for a wide range of unstable fissile nuclei. In addition, quasi-free NN scattering represents a surrogate reaction to induce fission, allowing the complete identification of the fissioning system in terms of isotopic composition and excitation energy. The manuscript describes the technical realisation of these experiments as well as the physics programme and some preliminary results.
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Bottoni, S. et al, Gadea, A., & Perez-Vidal, R. M. (2025). Investigating the structure of 11B using particle-γ coincidences. Nucl. Phys. A, 1062, 123138–4pp.
Abstract: The structure of 11B was investigated at Legnaro National Laboratories of INFN using the 6Li(6Li,py) fusion-evaporation reaction. Emitted protons feeding excited states of 11B were detected by the GALTRACE silicon telescopes in coincidence with y rays measured by the GALILEO HPGe array. The level and y-decay scheme of 11B was reconstructed on an even-by-event basis by combining particle and y-ray spectroscopy techniques. In particular, the y decay from the possible near-threshold proton resonance was searched for, providing first results on its y-ray branch with a 5 sigma and 3 sigma confidence level. Results are discussed along with predictions of the Shell Model Embedded in the Continuum (SMEC).
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Pellumaj, J. et al, & Perez-Vidal, R. M. (2025). Investigating the collectivity of intruder states along N=49 isotones. Nucl. Phys. A, 1060, 123125–6pp.
Abstract: Intruder states that originate from the promotion of neutrons across the N=50 shell gap are observed along the N=49 isotones (79Zn, 81Ge, 83Se, 85Kr), with the lowest energy in 83Se. The reduction of the N=50 shell gap towards Ni favors the lowering in the energy of these states. Moreover, since the Se nucleus (Z=34) is in the middle of the proton fp-shell (28 <= Z <= 40), it should have the maximum quadrupole correlations, lowering further the energy of these deformed configurations. This makes Se a good candidate for understanding the collectivity of the particle-hole intruder states in this region. Such information could also be used as a testing ground for theoretical models aiming to describe the region in the vicinity of 78Ni. An experiment aiming to measure the lifetime of the 540-keV 1/2+ and 1100-keV 3/2+ intruder states of 83Se was performed at LNL and is reported in this work.
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Feijoo-Fontan, M., Barriere, A., Mozumdar, N., Alvarez-Pol, H., Rodriguez-Sanchez, J. L., Sorlin, O., et al. (2025). Development of a PID algorithm for the CALIFA detector to study multinucleon knockout reactions in exotic nuclei. Nucl. Phys. A, 1059, 123103–4pp.
Abstract: Previous studies have shown a reduction in cross sections relative to theoretical predictions for single-nucleon knockout reactions, with varying conclusions about the dependence of this reduction on the N/Z ratio of the projectile. The (p,pX) knockout reactions studied with the R3B setup offer a unique opportunity for kinematically complete measurements using inverse kinematics. This work focuses on the development of an algorithm for performing particle identification using the CALIFA detector, of vital importance for the study of knocked-out clusters such as deuterium.
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Syeda, N. K. et al, & Algora, A. (2025). Investigation of the excited states of 114Sn using the GRIFFIN spectrometer at TRIUMF. Nucl. Phys. A, 1059, 123090–5pp.
Abstract: The semi-magic 110-122Sn isotopes display signs of shape coexistence in their excited 0+ states, which, in contrast to the spherical 0+ ground states, are deformed. This paper investigates the nuclear structure of 114Sn using the competing /3+ decay and electron capture of a radioactive beam of 114Sb produced at the TRIUMF-ISAC facility using the GRIFFIN spectrometer. This study will allow for an in-depth understanding of the excited 0+ states in 114Sn, by focusing on their decay patterns. In the present experiment, transitions at 856.2-keV and 1405.0-keV, which were observed in an earlier /3+ decay study but not placed in the 114Sn level scheme, have been Physics, assigned to the level scheme in connection to the 0+3 level at 2156.0-keV. Properly assigning these transitions refines the level scheme and enhances our understanding of the nuclear structure in 114Sn.
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NA64 Collaboration(Andreev, Y. M. et al), Molina Bueno, L., & Tuzi, M. (2023). Measurement of the intrinsic hadronic contamination in the NA64-e high-purity e+/e- beam at CERN. Nucl. Instrum. Methods Phys. Res. A, 1057, 168776–8pp.
Abstract: We present the measurement of the intrinsic hadronic contamination at the CERN SPS H4 beamline configured to transport electrons and positrons at 100 GeV/c. The analysis, performed using data collected by the NA64-e experiment in 2022, is based on calorimetric measurements, exploiting the different interaction mechanisms of electrons and hadrons in the NA64 detector. We determined the contamination by comparing the results obtained using the nominal electron/positron beamline configuration with those from a dedicated setup, in which only hadrons impinged on the detector. We also obtained an estimate of the relative protons, antiprotons and pions yield by exploiting the different absorption probabilities of these particles in matter. We cross-checked our results with a dedicated Monte Carlo simulation for the hadron production at the primary T2 target, finding a good agreement with the experimental measurements.
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Mollaebrahimi, A. et al: A., S. (2025). First observation of MNT isotope beams at the FRS Ion Catcher. Nucl. Phys. A, 1057, 123041–4pp.
Abstract: An exploratory experiment on Multi-Nucleon Transfer (MNT) reactions was successfully conducted at the FRS Ion Catcher setup at GSI. The experiment demonstrated the production of MNT-driven radioactive ion beams (RIBs) produced by decelerated relativistic beams. A beam of 238U ions was reacted with a 209Bi target at near-Coulomb barrier energies inside the specially modified Cryogenic Stopping Cell (CSC) for the production and thermalization of MNT products. These products were then identified using a Multiple-Reflection Time-Of-Flight Mass Spectrometer (MRTOF-MS). The observation of target-like MNT fragments along the A = 211 isobaric chain provided a proof-of-principle for future MNT studies with the FRS Ion Catcher setup.
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R3B Collaboration(Ponnath, L. et al), Benlliure, J., Cortina-Gil, D., & Nacher, E. (2025). Precise measurement of nuclear interaction cross sections towards neutron-skin determination with R3B. Nucl. Phys. A, 1056, 123022–5pp.
Abstract: The (RB)-B-3 (Reactions with Relativistic Radioactive Beams) experiment as a major instrument of the NUSTAR collaboration for the research facility FAIR in Darmstadt is designed for kinematically complete studies of reactions with high-energy radioactive beams. Part of the broad physics program of (RB)-B-3 is to constrain the asymmetry term in the nuclear equation-of-state and hence improve the description of highly asymmetric nuclear matter (e.g., in neutron stars). For a precise determination of the neutron-skin thickness – an observable which is directly correlated with the symmetry energy in theoretical calculations – by measuring absolute fragmentation cross sections, it is essential to quantify the uncertainty and challenge the reaction model under stable conditions. During the successful FAIR Phase-0 campaign of (RB)-B-3, we precisely measured the energy dependence of total interaction cross sections in C-12+C-12 collisions, for a direct comparison with calculations based on the eikonal reaction theory.
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