Tue·Sep 23, 2025Tuesday·September 23, 2025

1. 01*

   Measurement of ${}^{3,4}$He($K^{-},{\pi }^0$)${}_{\Lambda }^{3,4}$H reaction cross section and evaluation of hypertriton $\Lambda$ binding energy

   T. Akaishi🇯🇵 · H. Asano🇯🇵 · X. Chen🇨🇳 · A. Clozza🇮🇹 · C. Curceanu🇮🇹 · R. Del Grande🇮🇹 · C. D. Han🇨🇳 · T. Hashimoto🇯🇵 · M. Iliescu🇮🇹 · K. Inoue🇯🇵 · S. Ishimoto🇯🇵 · K. Itahashi🇯🇵 and 23 other authors

   Light $s$-shell hypernuclei (${}_{\Lambda }^{3,4}\text{H}$) and their ground-state properties are crucial benchmarks in hypernuclear physics. In particular, comparing the production cross sections of ${}_{\Lambda }^3\text{H}$ and ${}_{\Lambda }^4\text{H}$ provides insights into the $\Lambda N$ interaction in different isospin configurations, which can help address recent discrepancies in the reported $\Lambda$ binding energy of hypertriton. We present the first measurement of the production cross sections for ${}_{\Lambda }^3\text{H}$ and ${}_{\Lambda }^4\text{H}$ using the in-flight $(K^{-},{\pi }^0)$ reaction at a beam momentum of 1.0 GeV/$c$ with an identical experimental setup. The production cross sections in the laboratory frame, for the angular range from 0${}^{\circ }$ to 20${}^{\circ }$, are measured to be $15.0\pm 2.6(\text{stat.}){}_{-2.8}^{+2.4}(\text{syst.})\mu \text{b}$ and $49.9\pm 2.1(\text{stat.}){}_{-8.0}^{+7.8}(\text{syst.})\mu \text{b}$ for the ground-state of ${}_{\Lambda }^3\text{H}$ and ${}_{\Lambda }^4\text{H}$, respectively. Using the ratio of these cross sections and comparing it with theoretical calculations, we evaluate the $\Lambda$ binding energy of hypertriton, yielding a value consistent with the picture of a loosely bound system.

   nucl-exPLB(2026)·4 citations
2. 02*

   A high-voltage MR-ToF mass spectrometer and separator for the study of exotic isotopes at FRIB

   F.M. Maier🇺🇸 · C.M. Ireland🇺🇸 · G. Bollen🇺🇸 · E. Dhayal · T. Fowler-Davis · E. Leistenschneider🇺🇸 · M.P. Reiter🇬🇧 · R. Ringle🇺🇸 · S. Schwarz🇺🇸 · A. Sjaarda

   The Facility for Rare Isotope Beams (FRIB) delivers a wide variety of rare isotopes as fast, stopped, or reaccelerated beams to enable forefront research in nuclear structure, astrophysics, and fundamental interactions. To expand the scientific potential of FRIB's stopped and reaccelerated beam programs, we are designing a Multi-Reflection Time-of-Flight mass spectrometer and separator (MR-ToF MS). It will enable high-precision mass measurements of short-lived isotopes, improve beam diagnostics, and deliver isobarically and isomerically purified beams to downstream experimental stations. It is designed to store ions at a kinetic energy of 30 keV, significantly enhancing ion throughput while maintaining high mass resolving power. We present the scientific motivation, technical design, and simulations demonstrating the expected performance of the system, which has the potential to significantly enhance FRIB's mass measurement, diagnostic, and mass separation capabilities.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2026)·2 citations
3. 03*

   Equation of state for hyperonic neutron-star matter in SU(3) flavor symmetry

   Tsuyoshi Miyatsu🇰🇷 · Myung-Ki Cheoun🇰🇷 · Kyungsik Kim🇰🇷 · Koichi Saito🇯🇵

   Using a relativistic mean-field model calibrated to finite-nucleus observables and bulk properties of dense nuclear matter, we investigate hyperonic neutron-star matter within an SU(3) flavor-symmetry scheme. To retain SU(6)-based couplings within SU(3) flavor symmetry, we add a quartic $\varphi$ self-interaction and $\varphi$-$\rho$ mixing. We demonstrate the roles of ${\alpha }_v$ ($F/(F+D)$ ratio), ${\theta }_v$ (mixing angle), and $z_v$ (singlet-to-octet coupling ratio) in SU(3)-invariant vector-meson couplings. It is found that $z_v$ predominantly controls the maximum mass of a neutron star, and $2M_{\odot }$ neutron stars can be supported for $z_v\le 0.15$. The ${\alpha }_v$ also helps sustain large masses, whereas ${\theta }_v$ has a smaller effect on neutron-star properties. This SU(3) framework reconciles nuclear and astrophysical constraints, and offers a plausible resolution to the hyperon puzzle.

   ↳ nucl-thastro-ph.HEnucl-exSymmetry(2025)·7 citations
4. 04*

   Solution to the uncertainty problem of nuclear matrix element for neutrinoless double-$\beta$ decay

   J. Terasaki🇨🇿 · O. Civitarese🇦🇷

   The neutrinoless double-$\beta$ decay ($0\nu \beta \beta$) of nuclei is one of the major research subjects of neutrino physics nowadays because of its influence on particle physics and astrophysics. The predicted nuclear matrix elements (NMEs) for the $0\nu \beta \beta$ decay exhibit large uncertainties depending on the models employed. This problem has affected the development of neutrino physics for many years. We have recently performed the calculation of the NMEs for the $0\nu \beta \beta$ and two-neutrino double-$\beta$ decay ($2\nu \beta \beta$) modes with a perturbed transition operator and found that the effective axial-vector current coupling $g_A^{\mathrm{eff}}$ is similar for the two decay modes. Based on this finding, we calculate the $0\nu \beta \beta$ NMEs using the phenomenological $g_A^{\mathrm{eff}}$ that reproduces the measured half-life of the $2\nu \beta \beta$ decay. We apply this method to the NMEs for ${}^{136}$Xe, ${}^{130}$Te, and ${}^{76}$Ge obtained by several groups and show that the uncertainty of the $0\nu \beta \beta$ NME is dramatically reduced. Based on this result, we calculate the effective neutrino mass, consistent with the current experimental lower limit of the half-life for the $0\nu \beta \beta$ decay. The results indicate that the extracted value of the effective neutrino mass does not yet reach the inverted-mass-hierarchy region allowed by neutrino oscillation data when the lightest neutrino mass is assumed to be below 10 meV. We also calculate the perturbed $0\nu \beta \beta$ and $2\nu \beta \beta$ NMEs of ${}^{110}$Pd.

   ↳ nucl-thhep-phnucl-ex0 citations
5. 05*

   Facilitating neutron and energy reconstruction in neutrino events using the direction of tagged neutrons

   Steven Manly🇺🇸 · Mitchell Lahare🇺🇸 · Hilary Utaegbulam🇺🇸 · David Last🇺🇸

   To date, accelerator neutrino experiments have had only limited success including neutrons in the neutrino event reconstruction event by event. Produced neutrons often interact in a detector leaving an energy deposition that does not correlate strongly with the kinetic energy of the neutron. This work explores the inclusion of the direction of a neutron tagged by such an energy deposition in concert with the missing transverse momentum of the reconstructed particles to determine the approximate kinetic energy of the neutron and modify the reconstruction of the energy of the incoming neutrino. The technique significantly increases the neutron kinetic energy estimation relative to one that assigns the neutron kinetic energy by enforcing transverse momentum balance alone. When included in the neutrino energy calculation, the neutrino energy resolution is improved and the reconstructed energy is distributed more symmetrically around the true value. The technique shows promise and might be used to good effect to analyze data taken with experiments able to tag neutron energy deposits with good neutron direction resolution such as the T2K near detector and the liquid argon detectors in the SBN program and DUNE.

   ↳ hep-exnucl-ex1 citation
6. 06*

   Gas-jet target with online interferometric thickness measurement for nuclear astrophysics

   Anup Yadav🇮🇳 · Daniel Bemmerer🇩🇪 · Fabian Donat · Juozas Dudutis · Sören Göhler · Maik Görler · Maxim Hilz · Arie Irman · Migle Mackeviciute · Konrad Schmidt🇩🇪 · Manfred Sobiella · Vidmantas Tomkus · Kai Zuber🇩🇪

   A new jet gas target system has been developed for the Felsenkeller 5 MV underground ion accelerator for nuclear astrophysics. It provides either a 1.5$\times 10^{18}$ cm${}^{-2}$ thick cylindrical jet or a 7$\times 10^{17}$ cm${}^{-2}$ thick wall of nitrogen gas, with a surface of 10$\times$10 mm${}^2$ to be seen by the ion beam. The system includes a de Laval type nozzle and altogether five pumping stages: In addition to the jet catcher and the jet chamber surrounding it, there are three stages connecting the jet to the ion accelerator. Behind the jet chamber, as seen from the ion beam, a windowless static-type gas target and, subsequently, a beam calorimeter have been installed. This work describes the offline tests of the gas target system prior to its installation on the beam line of the Felsenkeller accelerator. The thickness of the jet has been determined using three different methods: By computational fluid dynamics simulations, with a Mach-Zehnder interferometer, and by $\alpha$-energy loss using a mixed $\alpha$ source. The three methods were shown to be in agreement. For 0-6 bar inlet gas pressure, a linear relationship between inlet pressure and jet thickness has been found. Different shapes of de Laval type inlet nozzles, both circular and slit-type, have been manufactured from fused silica glass or stainless steel and tested using measurements and simulations. The power and stability of the beam calorimeter have been tested. The interferometry has been shown to work reliably and to give two-dimensional projections of the gas jet with sub-mm resolution.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2026)·1 citation
7. 07*

   Particle Identification with MLPs and PINNs Using HADES Data

   Marvin Kohls🇩🇪

   In experimental nuclear and particle physics, the extraction of high-purity samples of rare events critically depends on the efficiency and accuracy of particle identification (PID). In this work, we present a PID method applied to HADES data at the level of fully reconstructed particle track candidates. The results demonstrate a significant improvement in PID performance compared to conventional techniques, highlighting the potential of physics-informed neural networks as a powerful tool for future data analyses.

   ↳ physics.data-annucl-ex0 citations
8. 08*

   Dineutron clusters in ${}^7$He and ${}^8$He structure

   E. Garrido🇪🇸 · A.S. Jensen

   The hyper-radial barrier strongly hinders formation of more than three clusters. We investigate how well the dominating cluster components in ${}^7$He and ${}^8$He, respectively can be described as $\alpha$+$n$+${}^{2}n$ and $\alpha$+${}^{2}n$+${}^{2}n$, where ${}^{2}n$ is the dineutron. Effective interactions compatible with ${}^5$He and ${}^6$He are used. We vary the lesser known $n$-${}^{2}n$ and ${}^{2}n$-${}^{2}n$ interactions, where very small strengths are required. We provide energies, radii, and partial wave decomposition of all computed, predicted or measured, ground and resonance states. We predict substructures within each of the three-body quantum states. We also calculate the neutron-structure sensitive invariant mass spectrum of the four-nucleon system, after fast removal of the $\alpha$-particle from ${}^8$He. We show that all available experimental information are fairly well reproduced. Very little room is left for variation of the effective interaction parameters. Thus, the dominating features of the subsequently derived reaction and structure properties are well supported.

   ↳ nucl-thnucl-exJ.Phys.G(2025)·1 citation

* 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.