Wed·Apr 16, 2025Wednesday·April 16, 2025

1. 01*

   Deciphering Spin-Parity Assignments of Nuclear Levels

   Christian Iliadis🇺🇸

   Spin-parity assignments of nuclear levels are critical for understanding nuclear structure and reactions. However, inconsistent notation conventions and ambiguous reporting in research papers often lead to confusion and misinterpretations. This paper examines the policies of the Evaluated Nuclear Structure Data File (ENSDF) and the evaluations by Endt and collaborators, highlighting key differences in their approaches to spin-parity notation. Sources of confusion are identified, including ambiguous use of strong and weak arguments and the conflation of new experimental results with prior constraints. Recommendations are provided to improve clarity and consistency in reporting spin-parity assignments, emphasizing the need for explicit notation conventions, clear differentiation of argument strengths, community education, and separate reporting of new findings. These steps aim to enhance the accuracy and utility of nuclear data for both researchers and evaluators.

   nucl-exEPJA(2025)·2 citations
2. 02*

   Isomeric yield ratios and mass spectrometry of Y and Nb isotopes in the neutron-rich N=60 region: the unusual case of ${}^{98}$Y

   Simone Cannarozzo🇸🇪 · Stephan Pomp🇸🇪 · Anu Kankainen🇫🇮 · Iain Moore🇫🇮 · Marek Stryjczyk🇫🇮 · Ali Al-Adili · Andreas Solders · Ville Virtanen🇫🇮 · Tommi Eronen🇫🇮 · Zhihao Gao🇨🇳 · Zhuang Ge · Arthur Jaries🇫🇮 and 5 other authors

   The isomeric yield ratio (IYR) of fission products is an observable that carries relevant information about the fragments emerging from the scission of a fissioning nucleus. We report on IYR of ${}^{96,98,100}$Y and ${}^{100,102}$Nb, together with the previously reported values for ${}^{97}$Y and ${}^{99}$Nb, produced in the 28 MeV $\alpha$-induced fission of ${}^{232}$Th at the Ion Guide Isotope Separation On-Line (IGISOL) facility of the University of Jyväskylä. We measured the IYR using two different techniques, the phase-imaging ion-cyclotron-resonance (PI-ICR) and the multiple-reflection time-of-flight mass spectrometry (MR-TOF-MS) methods. Moreover, we measured the masses of the long-lived states in ${}^{98,100}$Y and ${}^{100,102}$Nb populated via in-trap $\beta$-decay of their precursors. Since the $\beta$-decay selectively populates states with a favourable spin-parity, we could identify the measured state and show that the ground state is the low-spin state in the cases of ${}^{98}$Y and ${}^{100}$Nb, while it is the high-spin state in the cases of ${}^{100}$Y and ${}^{102}$Nb. This measurement confirms the spin-parity assignments of all the nuclei as they are reported in the NUBASE2020 evaluations, disagreeing with the assignment for ${}^{100}$Y reported in the ENSDF evaluation. Making also use of previously reported data, we observe an anomalously low IYR for the $N=59$ isotope ${}^{98}$Y as compared to other yttrium or neighboring niobium isotopes. This behavior is very rare across the nuclear chart and is posited to be connected to the characteristic shape coexistence of ${}^{98}$Y, and to the change in the charge radii of the ground and excited states in the $N=58-60$ region.

   nucl-exPLB(2025)·2 citations
3. 03*

   Structure and dynamics of open-shell nuclei from spherical coupled-cluster theory

   Francesco Marino🇩🇪 · Francesca Bonaiti🇺🇸 · Sonia Bacca🇩🇪 · Gaute Hagen🇺🇸 · Gustav R. Jansen🇺🇸

   We extend the spherical coupled-cluster ab initio method for open-shell nuclei where two nucleons are removed from a shell subclosure. Following the recent implementation of the two-particle attached approach [Phys. Rev.C 110 (2024) 4, 044306], we focus on the two-particle-removed method. Using the equations-of-motion framework, we address both nuclear structure and dipole response functions by coupling coupled-cluster theory with the Lorentz integral transform technique. We perform calculations using chiral interactions, including three-nucleon forces, and estimate many-body uncertainties by comparing different coupled-cluster truncation schemes. We validate our approach by studying ground-state energies, excited states, and electric dipole polarizabilities in the oxygen and calcium isotopic chains. For binding energies and selected low-lying excited states, we achieve an accuracy comparable to that of the established closed-shell coupled-cluster theory and generally agree with experiment. Finally, we underestimate experimental data for electric dipole polarizabilities, particularly in calcium isotopes.

   ↳ nucl-thnucl-exPRC(2025)·10 citations
4. 04*

   Fusion research in a Deuterium-Tritium tokamak

   E. R. Solano

   The recent ITER re-baselining calls for new fusion-relevant research best carried out in a DT-capable tokamak device with similar technical choices. The present paper describes key issues that could be addressed in a Suitably Enhanced DT-capable Tokamak (SET), with tungsten plasma facing components, boronization systems, and 10 MW of ECRH, based on JET's characteristics and knowledgebase. We discuss hardware options, and show that fusion-relevant operational scenarios could be achieved. Notably, development, validation and testing of fusion and nuclear diagnostics, to be used in next generation devices, would require a DT-capable tokamak as described.

   ↳ physics.plasm-phnucl-exPlasma Phys.(2025)·1 citation
5. 05*

   Multireference covariant density functional theory for shape coexistence and isomerism in ${}^{43}$S

   E. F. Zhou · X. Y. Wu🇨🇳 · J. Xiang · J. M. Yao🇨🇳 · P. Ring

   We extend the multireference covariant density functional theory (MR-CDFT) to describe the low-lying states of the odd-mass nucleus ${}^{43}$S near the neutron magic number $N=28$ with shape coexistence. The wave functions of the low-lying states are constructed as superpositions of configurations with different intrinsic shapes and $K$ quantum numbers, projected onto good particle numbers and angular momenta. The MR-CDFT successfully reproduces the main features of the low-energy structure in ${}^{43}$S. Our results indicate that the ground state, $3/2_1^{-}$, is predominantly composed of the intruder prolate one-quasiparticle (1qp) configuration $\nu 1/2^{-}[321]$. In contrast, the $7/2_1^{-}$ state is identified as a high-$K$ isomer, primarily built on the prolate 1qp configuration $\nu 7/2^{-}[303]$. Additionally, the $3/2_2^{-}$ state is found to be an admixture dominated by an oblate configuration with $K^{\pi }=1/2^{-}$, along with a small contribution from a prolate configuration with $K^{\pi }=3/2^{-}$. These results demonstrate the capability of MR-CDFT to capture the intricate interplay among shape coexistence, $K$-mixing, and isomerism in the low-energy structure of odd-mass nuclei around $N=28$.

   ↳ nucl-thnucl-exNucl.Sci.Tech.(2026)·3 citations
6. 06*

   The Gaseous Prototype (GaP): a GanESS demonstrator

   L. Larizgoitia🇪🇸 · A. Simón🇪🇸 · E. Oblak🇪🇸 · C. Echeverria🇪🇸 · P. Dietz🇪🇸 · A. Castillo🇪🇸 · L. Donneger🇪🇸 · J.J. Gómez-Cadenas🇪🇸 · F. Monrabal🇪🇸

   The GanESS experiment will exploit the high-pressure noble gas time projection chamber technology to detect coherent elastic neutrino-nucleus scattering (CE$\nu$NS) at the European Spallation Source (ESS). The detector, able to operate at pressures up to 50 bar with different noble gases (Xe, Ar and Kr), will employ electroluminescence to amplify the ionization signal with the objective of reaching a threshold as low as 1-2 e${}^{-}$, equivalent to $<$ 100 eV${}_{\text{ee}}$. The Gaseous Prototype (GaP) has been built to characterize the technique at the few-keV energy regime and to understand various aspects related to the technology. Concretely, it will be used to measure the quenching factor of the different mediums as well as to characterize the electroluminescence yield and detection threshold under different operational conditions. The present paper describes the Gaseous Prototype and its first results operating with gaseous argon at moderate pressures (up to 10 bar). A potential detection threshold lower than 2.9 keV has been observed following operation with a ${}^{55}$Fe calibration source.

   ↳ physics.ins-dethep-exnucl-ex1 citation
7. 07*

   Combined Evidence for the $X_{17}$ Boson After PADME Results on Resonant Production in Positron Annihilation

   Fernando Arias-Aragón🇮🇹 · Giovanni Grilli di Cortona🇮🇹 · Enrico Nardi🇮🇹 · Claudio Toni🇫🇷

   The Positron Annihilation into Dark Matter Experiment at the Laboratori Nazionali di Frascati has reported an excess of $e^{+}{e}^{-}$ final-state events from positron annihilation on fixed-target atomic electrons. While the global significance remains at the $(1.77\pm 0.15)\sigma$ level, the excess is centered around $\sqrt{s}\sim 17\text{MeV}$, coinciding with the invariant mass at which anomalous $e^{+}{e}^{-}$ pair production has previously been observed in nuclear transitions from excited to ground states in ${}^8$Be, ${}^4$He and ${}^{12}$C, thereby strengthening the case for a common underlying origin, possibly involving a hypothetical new $X_{17}$ boson. We discuss the significance of this independent accelerator-based evidence. Combining it with existing nuclear physics results, we obtain a value for the $X_{17}$ mass of $m_{X_{17}}=16.88\pm 0.05\text{MeV}$, reducing the uncertainty from nuclear physics determinations by more than a factor of two, and mitigating the impact of poorly known correlations among their systematic errors.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2026)·11 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.