Fri·Dec 6, 2024Friday·December 6, 2024

1. 01*

   Beta delayed neutron emission of $N=84$ ${}^{132}$Cd

   M. Madurga🇺🇸 · Z.Y. Xu🇺🇸 · 1 R. Grzywacz🇺🇸 · M.R. Mumpower🇺🇸 · A. Andreyev🇬🇧 · G. Benzoni🇮🇹 · M.J.G. Borge🇪🇸 · C. Costache🇷🇴 · I. Cox🇺🇸 · S. Cupp🇺🇸 · B. Dimitrov🇧🇬 · P. Van Duppen🇧🇪 and 45 other authors

   Using the time-of-flight technique, we measured the beta-delayed neutron emission of ${}^{132}$Cd. From our large-scale shell model (LSSM) calculation using the N${}^3$LO interaction [Z.Y. Xu et al., Phys. Rev. Lett. 131, 022501 (2023)], we suggest the decay is dominated by the transformation of a neutron in the $g_{7/2}$ orbital, deep below the Fermi surface, into a proton in the $g_{9/2}$ orbital. We compare the beta-decay half-lives and neutron branching ratios of nuclei with $Z<50$ and $N\ge 82$ obtained with our LSSM with those of leading "global" models such as Finite-Range Droplet Model (FRDM). Our calculations match known half-lives and neutron branching ratios well and suggest that current leading models overestimate the yet-to-be-measured half-lives. Our model, backed by the ${}^{132}$Cd decay data presented here, offers robust predictive power for nuclei of astrophysical interest such as $r$-process waiting points.

   nucl-exnucl-thPRL(2026)·0 citations
2. 02*

   Disentangling the influence of excitation energy and compound nucleus angular momentum on fission fragment angular momentum

   Simone Cannarozzo🇸🇪 · Stephan Pomp🇸🇪 · Andreas Solders · Ali Al-Adili · Zhihao Gao🇨🇳 · Mattias Lantz · Heikki Penttilä · Anu Kankainen🇫🇮 · Iain Moore🇫🇮 · Tommi Eronen🇫🇮 · Jouni Ruotsalainen🇫🇮 · Zhuang Ge🇫🇮 and 5 other authors

   The origin of the large angular momenta observed for fission fragments is still a question under discussion. To address this, we study isomeric yield ratios (IYR), i.e. the relative population of two or more long-lived metastable states with different spins, of fission products. We report on IYR of 17 isotopes produced in the 28 MeV $\alpha$-induced fission of ${}^{232}$Th at the IGISOL facility of the University of Jyväskylä. The fissioning nuclei in this reaction are ${}^{233,234,235}$U*. We compare our data to IYR from thermal neutron-induced fission of ${}^{233}$U and ${}^{235}$U, and we observe statistically significant larger IYR in the ${}^{232}$Th($\alpha$,f) reaction, where the average compound nucleus (CN) spin is 7.5 $\hslash$, than in ${}^{233,235}$U(n${}_{th}$,f), with average spins 2.5 and 3.5 $\hslash$, respectively. To assess the influence of the excitation energy, we study literature data of IYR from photon-induced fission reactions, and find that the IYR are independent of the CN excitation energy. We conclude that the different IYR must be explained by the different CN spin alone. This implies that the FF angular momentum only partly comes from the fission process itself, and is in addition influenced by the angular momentum present in the CN.

   nucl-exnucl-thPRC(2025)·5 citations
3. 03*

   A simple model to investigate jet quenching and correlated errors for centrality-dependent nuclear-modification factors in relativistic heavy-ion collisions

   Ron A Soltz🇺🇸 · Dhanush A Hangal🇺🇸 · Aaron Angerami🇺🇸

   We apply Bayesian techniques to compare a simple, empirical model for jet-quenching in heavy-ion collisions to centrality-dependent jet-$R_{AA}$ measured by ATLAS for Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$~TeV. We find that the $R_{AA}$ values for central collisions are adequately described with a model for the mean $p_T$-dependent jet energy-loss using only 2-parameters. This model is extended by incorporating 2D initial geometry information from TRENTO and compared to centrality-dependent $R_{AA}$ values. We find that the results are sensitive to value of the jet-quenching formation time, ${\tau }_f$, and that the optimal value of ${\tau }_f$ varies with the assumed path-length dependence of the energy-loss. We construct a covariance error matrix for the data from the $p_T$ dependent contributions to the ATLAS systematic errors and perform Bayesian calibrations for several different assumptions for the systematic error correlations. We show that most-probable functions and ${\chi }^2$ values are sensitive to assumptions made when fitting to correlated errors.

   ↳ nucl-thhep-phnucl-exPRC(2025)·7 citations
4. 04*

   Development of decay energy spectroscopy for radio impurity analysis

   J.S. Chung · O. Gileva🇰🇷 · C. Ha🇰🇷 · J.A Jeon🇰🇷 · H.B. Kim🇰🇷 · H.L. Kim🇰🇷 · Y.H. Kim🇰🇷 · H.J. Kim · M.B Kim · D.H. Kwon🇰🇷 · D.S. Leonard🇰🇷 · D.Y. Lee and 4 other authors

   We present the development of a decay energy spectroscopy (DES) method for the analysis of radioactive impurities using magnetic microcalorimeters (MMCs). The DES system was designed to analyze radionuclides, such as Ra-226, Th-228, and their daughter nuclides, in materials like copper, commonly used in rare-event search experiments. We tested the DES system with a gold foil absorber measuring 20x20x0.05 mm^3, large enough to accommodate a significant drop of source solution. Using this large absorber and an MMC sensor, we conducted a long-term measurement over ten days of live time, requiring 11 ADR cooling cycles. The combined spectrum achieved an energy resolution of 45 keV FWHM, sufficient to identify most alpha and DES peaks of interest. Specific decay events from radionuclide contaminants in the absorber were identified. This experiment confirms the capability of the DES system to measure alpha decay chains of Ra-226 and Th-228, offering a promising method for radio-impurity evaluation in ultra-low background experiments.

   ↳ physics.ins-detnucl-ex0 citations
5. 05*

   Performance study for anisotropic flow measurements in the MPD (NICA) experiment with fixed target

   P. Parfenov🇷🇺 · M. Mamaev🇷🇺 · A. Taranenko🇷🇺

   Studying the properties of strongly-interacting matter at high relative baryon densities is one of the key scientific goals of the MPD (Multi-Purpose Detector) experiment at the NICA accelerator complex. The performance of measuring the azimuthal collective flow of identified charged hadrons at the MPD facility in fixed-target mode is studied in this work.

   ↳ hep-exnucl-exphysics.ins-det0 citations
6. 06*

   Spin distribution of fission fragments involving bending and wriggling modes

   D.E. Lyubashevsky · A.A. Pisklyukov · Yu.D. Shcherbina · T.Yu. Shashkina · P.V. Kostryukov

   We present a closed analytical description of the spin distributions of the fragments produced in low-energy induced and spontaneous fission. In our model the high fragment spins and the relative orbital angular momentum arise from the zero-point transverse wriggling and bending oscillations of the two pre-fragments, under the postulate that the fissioning system remains ``cold'' up to scission -- its available energy being stored as non-equilibrium deformation rather than as heat. From the probability distributions of the two modes we derive a closed expression for the spin distribution of each fragment and for its mean value. The decisive quantities are the fragment moments of inertia, which we evaluate in the hydrodynamic model from the non-equilibrium scission deformations reconstructed from the measured prompt-neutron multiplicities. Confronted with the recent data on ${}^{232}\mathrm{Th}(\mathrm{n},\mathrm{f})$, ${}^{238}\mathrm{U}(\mathrm{n},\mathrm{f})$, and ${}^{252}\mathrm{Cf}(\mathrm{sf})$, the model reproduces both the magnitude of the mean spins and their characteristic sawtooth dependence on the fragment mass. Comparison with the statistical and microscopic approaches indicates that the differences for individual fragments can be traced largely to the deformation dependence of the moments of inertia.

   ↳ nucl-thnucl-exPhys.Atom.Nucl.(2024)·3 citations
7. 07*

   Estimation of correlation coefficients and spin angular distributions of fission fragments

   D.E. Lyubashevsky · A.A. Pisklyukov · S.V. Klyuchnikov · P.V. Kostryukov

   This study proposes a theoretical model for studying the spin characteristics and angular correlations of fission fragments of heavy nuclei. The mechanisms of spin formation, including the influence of transverse vibrations, are considered and the relationship between the anisotropy of the angular distribution and the correlation coefficient is revealed. The theoretical predictions are compared with experimental data and various models developed by other research groups.

   ↳ nucl-thnucl-exPRC(2025)·1 citation
8. 08*

   Ab initio calculations of overlap integrals for $\mu \to e$ conversion in nuclei

   Matthias Heinz🇩🇪 · Martin Hoferichter🇨🇭 · Takayuki Miyagi🇩🇪 · Frederic Noël🇨🇭 · Achim Schwenk🇩🇪

   The rate for $\mu \to e$ conversion in nuclei is set to provide the most stringent test of lepton-flavor symmetry and a window into physics beyond the Standard Model. However, to disentangle new lepton-flavor-violating interactions, in combination with information from $\mu \to e\gamma$ and $\mu \to 3e$, it is critical that uncertainties at each step of the analysis be controlled and fully quantified. In this regard, nuclear response functions related to the coupling to neutrons are notoriously problematic, since they are not directly constrained by experiment. We address these shortcomings by combining ab initio calculations with a recently improved determination of charge distributions from electron scattering by exploiting strong correlations among charge, point-proton, and point-neutron radii and densities. We present overlap integrals for ${}^{27}$Al, ${}^{48}$Ca, and ${}^{48}$Ti including full covariance matrices, allowing, for the first time, for a comprehensive consideration of nuclear structure uncertainties in the interpretation of $\mu \to e$ experiments.

   ↳ nucl-thhep-exhep-phnucl-exPLB(2025)·16 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.