We estimate both the polarization of spin $1/2$ baryons and the spin density matrix coefficients of spin 1 mesons using a thermal model that incorporates vorticity and polarization to describe quarks, along with a coalescence formalism where spin and vorticity are not in equilibrium. We find that while our model is not predictive due to its considerable number of free parameters, it has the potential to explain several seemingly puzzling features of experimental spin measurements, such as the absence of baryon polarization alongside significant vector meson spin alignment. We suggest measuring meson spin off-diagonal matrix elements, and examining the dependence of polarization observables on azimuthal angles, as methods to falsify this model and gain insights into the freeze-out details of baryon and meson spin structure.

We systematically discuss the decay patterns of the hidden-strange hadronic molecular state $N\left(2270\right)$ which is assumed to be an $s$-wave $K^{*}{\mathrm{\Sigma }}^{*}$ shallow bound state with possible quantum numbers $J^P$ of ${1/2}^{-}, {3/2}^{-}$, and ${5/2}^{-}$. By using the effective Lagrangian approach and considering pseudoscalar meson and vector meson exchanges, we thoroughly calculate and discuss the decay behavior of the $N\left(2270\right)$ molecular state, including hadronic and radiative decay and the cutoff dependence, for different $J^P$ values. For all three cases, the $K^{*}\mathrm{\Lambda }$ final state is always included as the main decay channel. However, the $K\mathrm{\Sigma }, K\mathrm{\Lambda }, K{\mathrm{\Sigma }}^{*}$, and $\pi \mathrm{\Delta }$ final states exhibit notable differences. These different decay properties will provide valuable guidance for future experimental searches and aid in distinguishing different $J^P$ assumptions and understanding their internal structures.

We analyze threshold photoproduction of heavy mesons off a deuteron and helium-4, using the QCD factorization method. Assuming large skewness, the production amplitude is dominated by the leading twist-2 gluonic energy-momentum tensor. We use our recent results for the gluonic gravitational form factors of light nuclei in the impulse approximation, to estimate the differential cross sections for $J/\mathrm{\Psi }$ production off a deuteron and helium-4 at current electron facilities.

The excited states of ${}^{93}\mathrm{Zr}$ have been investigated using the heavy-ion fusion-evaporation reaction ${}^{82}\mathrm{Se}({}^{18}\mathrm{O},\alpha 3n){}^{93}\mathrm{Zr}$ at the beam energies of 82 and 88 MeV. Particle-$\gamma \text{−}\gamma$ and $\gamma \text{−}\gamma$ coincidence measurements using CsI and HPGe arrays are employed to gain selectivity to Zr isotopic products. The level scheme of ${}^{93}\mathrm{Zr}$ was extended up to $E\approx 12.5\mathrm{Mev}$ and $I^{\pi }=(47/2^{-})$ with twenty-six new $\gamma$-ray transitions. The observation of $\gamma$ rays with $\approx 2\mathrm{Mev}$ and the associated fragmentation of the $\gamma$-ray flux into many competing pathways provide a clear experimental signature for the breaking core. Level structures in ${}^{93}\mathrm{Zr}$ were interpreted in the framework of the spherical shell model in a model space including the proton orbitals ($1f_{5/2}, 2p_{3/2}, 2p_{1/2}, 1g_{9/2}$) and neutron orbits ($1g_{9/2}, 1g_{7/2}, 2d_{5/2}, 1h_{11/2}$). A possible reduction of the $Z=38$ subshell spacing gap in ${}^{93}\mathrm{Zr}$ is discussed.

For quantum metastable problems with three particles, the ${}^6\mathrm{Be}$ and ${}^{16}\mathrm{Ne}$ nuclei as two-proton ($2p$) emitters provide a testing field. Considering the complexity of many-body metastable systems, a tractable solver has been on demand. We apply the analytic continuation in coupling constant (ACCC) to these nuclei, and confirm that this method can solve such problems consistently to the time-dependent results as well as to the experimental data. The sensitivity of the $2p$ energies and widths to the proton-proton interaction is also investigated. The ${}^6\mathrm{Be}$ shows a smooth shift from short-life to long-life systems according to the proton-proton interaction. Same is concluded for the $2^{+}$ resonance of ${}^{16}\mathrm{Ne}$. In contrast, for the first and second $0^{+}$ resonances of ${}^{16}\mathrm{Ne}$, their energies and widths show the avoid-crossing behavior, due to the coupling of two configurations in the core-proton subsystem ${}^{15}\mathrm{F}$. Since it requires only the bound-state solvers, the ACCC can be a low-cost option to solve three- or more-body resonances.

We perform a precision study of radii in Boron isotopes for multiple realistic interactions from chiral effective field theory. We obtain predictions of radii with combined many-body and interaction uncertainty quantification from ab initio no-core shell-model calculations together with machine-learning extrapolation methods. An extension to radius differences further allows us to investigate a potential proton halo in ${}^8\mathrm{B}$ and, moreover, provide predictions that relate directly to the isotope shift, which can be precisely measured in experiments.

The $\gamma$-ray strength function ($\gamma \mathrm{SF}$) is essential for understanding the electromagnetic response in atomic nuclei and modeling astrophysical neutron capture rates. We introduced a microscopic description of both electric dipole (E1) and magnetic dipole (M1) $\gamma \mathrm{SFs}$ that includes finite-temperature effects within relativistic density functional theory. The temperature dependence of the total electromagnetic $\gamma \mathrm{SFs}$ shows significant modification in the low-energy region due to thermal unblocking effects, essential for agreement with recent particle-$\gamma$ coincidence data from the Oslo method. An investigation of the electric and magnetic contributions to the total $\gamma \mathrm{SF}$ in hot nuclei indicates that the M1 mode becomes more prominent in the low-energy region, different than what is known at zero temperature. This microscopic approach offers new insights into the interplay between E1 and M1 $\gamma \mathrm{SFs}$ at finite temperature and opens new perspectives for future studies of $(n,\gamma )$ reactions and nucleosynthesis in hot stellar environments.

The $\alpha$-decay energy ($Q_{\alpha }$), deduced from nuclear binding energies, is often utilized to study nucleon-nucleon interaction and explore the structural property of exotic nuclei near the proton dripline. The systematics of available experimental $\alpha$-decay energies, in isotopic chains of heavy nuclei across the $N=126$ shell, behaves in a seeming contradiction with the shell-model picture: the lowest value of $Q_{\alpha }$ occurs at $N=124$, not $N=126$. This phenomenon can be effectively explained by investigating the mass differences, with the concentration on the contributions from the shell effect and pairing correlation through the macroscopic-microscopic mass model. The analysis is then extended to the region near the subshells of both $N=152$ and $N=162$, leading to the satisfactory reproduction of the experimental trend of decay energies as well. In addition, we present a detailed comparison with those results from the Finite-Range Droplet Model, the Hartree-Fock-Bogoliubov mass model, and the Weizsäcker-Skyrme mass formula, as accompanied by the similar pattern with respect to the experimental data.

Background: Predicting neutron-induced fission charge yields poses substantial challenges due to the complex, nonequilibrium nature of the fission process and the limited availability of detailed experimental data over a broad range of energies. Reliable modeling is essential for applications in reactor engineering, isotope production, and fundamental nuclear physics.

Purpose: This work aims to develop a robust probabilistic machine learning framework capable of accurately predicting neutron-induced fission charge yields under conditions of data scarcity. By incorporating methods that handle both epistemic (model-related) and aleatoric (data-inherent) uncertainties, the approach strives to represent physical phenomena such as odd-even effects and energy-dependent yields while providing realistic confidence intervals.

Method: A Bayesian mixture density network (BMDN) is introduced, combining three probabilistic components: (1) Gaussian process regression (GPR) to augment sparse datasets with synthetic samples and associated uncertainties; (2) Bayesian neural network (BNN) layers with an integrated attention mechanism that treats model parameters as random variables, capturing epistemic uncertainty through variational inference; and (3) a mixture density network (MDN) output layer that models charge yields as mixtures of Gaussian distributions, accommodating multimodal patterns and aleatoric uncertainty.

Results: The BMDN reproduces charge yield distributions for nuclei within the training set and generalizes effectively to previously unseen systems like ${}^{235}\mathrm{U}$. It accurately reflects odd-even staggering and energy dependence, with uncertainty intervals that correspond to both model confidence and intrinsic data variability. Comparisons against experimental data and semiempirical calculations demonstrate strong agreement with observed trends. While incorporating a white noise kernel in GPR enhances noise realism, it can soften subtle structural details, emphasizing the importance of balancing noise modeling with feature retention.

Conclusions: The presented approach provides a flexible, uncertainty-aware framework for predicting fission charge yields under sparse data conditions. By uniting GPR, BNN layers, and MDN outputs, the BMDN offers meaningful probabilistic insights and can guide future efforts toward more comprehensive datasets and improved theoretical models. Its adaptability makes it a promising tool for enhancing nuclear data evaluations, informing design choices in fission-related technologies, and advancing fundamental understanding of the fission process.

The kinetic energy of individual fission fragments for actinide nuclei is, for example, important for evaluating the prompt-neutron spectrum in the laboratory system. It is experimentally known that the kinetic energy for each fragment is constant at about $100\mathrm{MeV}$ for light fragments and that for heavy fragments decreases linearly with mass number. Most of the theoretical studies carried out so far attempted to calculate the total kinetic energy of both fragments, i.e., the sum of the energies of two fragments, but the kinetic energy of each fragment was not analyzed in detail as far as we recognize. We have calculated them in thermal-neutron-induced fission of ${}^{239}\mathrm{Pu}$ with a dynamical model using Langevin equations within a three-dimensional two-center parametrization. Also fission of ${}^{258}\mathrm{Fm}$ was investigated. It is calculated from the Coulomb energy at the scission point and the prescission kinetic energy. It is found that the prescission kinetic energy has about 2–4 % contribution in the kinetic energy. The calculated results reproduce the trend of the experimental data.

This paper presents the measurements of the angular differential cross sections for the forward production of He, Li, Be, B, C, and N nuclei in the fragmentation process of a $400\text{MeV/nucleon}{}^{16}\mathrm{O}$ beam interacting with a graphite target. Due to the limited data available in this energy regime, these measurements of nuclear fragmentation cross sections are relevant to improve nuclear interaction models for particle therapy and space radioprotection applications. The data analyzed in this paper were collected during a measurement campaign carried out at the GSI Helmholtz Center for Heavy Ion Research facility in Darmstadt (Germany) by the FOOT Collaboration. The results are compared with similar results found in the literature and with a previous FOOT measurement of the same process, using the same setup, from a previous pilot run performed at GSI. The pilot run data, however, had limited statistics and only allowed for the measurement of elemental fragmentation cross sections integrated in the setup acceptance. This data set, with statistics more than 100 times larger compared to the data collected in the previous run, enabled the measurement of angular differential cross sections, fully exploiting the granularity of the FOOT $\mathrm{\Delta }E$-TOF (time-of-flight) system. Furthermore, a better comprehension of the FOOT apparatus allowed to improve the analysis techniques, leading to a reduction in the final systematic uncertainties. The cross section results have been compared with some of the prominent Monte Carlo models of FLUKA and Geant4 dedicated to the energy range of interest for light ion fragmentation physics.

Charge-changing cross sections (CCCSs) of ${}^{18}\mathrm{O}$ on carbon (C) and lead (Pb) targets have been measured with an uncertainty of less than 4% near 370 MeV/nucleon. We evaluate the contributions of nucleon-nucleon and electromagnetic (EM) interactions to CCCSs by considering the direct proton removal process, the charged particle evaporation (CPE) after neutron removal, and the EM excitation. We conclude that the CPE accounts for 12.3 and 5% of CCCSs on C and Pb, respectively. Only less than 1% of CCCSs of ${}^{18}\mathrm{O}$ is attributed to the EM excitation. Further investigation of projectiles from ${}^{18}\mathrm{O}$ to ${}^{197}\mathrm{Au}$ on C, silver (Ag), and Pb targets at 300 and 900 MeV/nucleon shows that the EM contribution to CCCSs on Ag and Pb increases with projectile mass numbers and incident energies, and can reach 10% for ${}^{197}\mathrm{Au}$ on Pb at 900 MeV/nucleon. In contrast, the EM contribution to CCCS is negligible for all projectiles on C at both energies.

The decays of $N^{*}$ and ${\mathrm{\Delta }}^{*}$ resonances into $N\rho , \mathrm{\Delta }\pi$, and $N{f}_0\left(500\right)$ final states are investigated in a coupled-channel analysis of data from pion- and photoinduced reactions. Improvements in the fit quality are observed upon the inclusion of additional resonance contributions. Branching ratios for the intermediate isobars $\mathrm{\Delta }\left(1232\right)\pi , N\rho$, and $N{f}_0\left(500\right)$ are reported.

A theoretical understanding of a possible mechanism for synthesizing superheavy elements in the outer crust of magnetars is presented. We demonstrate that such a mechanism can be present whenever the baryon density in the outer crust of a neutron star reaches values around ${10}^{-2}$ ${\mathrm{fm}}^{-3}$. This scenario could be realized in magnetars with hypothetical large magnetic fields, $B\gtrsim {10}^{18}$ G. Under such conditions, the Coulomb lattice, formed by nuclei, enables a mechanism that synthesizes superheavy elements.

We systematically investigate how the choice between Gaussian and uniform likelihood functions in Bayesian inference affects the inferred bulk properties of compact stars and nuclear matter within covariant density functional-based equations of state. To enable direct comparison between the two approaches, we designed the uniform likelihood function with a Gaussian-equivalent normalization factor and marginalization behavior. Across three representative astrophysical scenarios, both approaches yield nearly identical mass-radius relations, density-pressure relations, and overlapping 95.4% confidence level regions. Although our inference analysis is carried out using parameters of the density functional, we subsequently determine the associated nuclear matter characteristic coefficients derived from the Taylor expansion of the energy density around the saturation density. We observe significant variation in the predicted isoscalar channel coefficients (e.g., the nuclear incompressibility) across different astrophysical scenarios, while the isovector channel (e.g., the slope of symmetry energy) exhibits only minimal variation.

Background: The radiative branching ratio of the Hoyle state is crucial to estimate the triple-$\alpha$ reaction rate in stellar environments at medium temperatures of $T=0.1$ to 2 GK. Knowledge of the $\gamma$-decay channel is critical as this is the dominant radiative decay channel for the Hoyle state. A recent study by Kibédi et al. [Phys. Rev. Lett. 125, 182701 (2020)] has challenged our understanding of this astrophysically significant branching ratio and its constraints.

Purpose: The main purpose was to perform a new measurement of the $\gamma$-decay branching ratio of the Hoyle state to deduce the radiative branching ratio of the Hoyle state. An additional objective was to independently verify aspects of the aforementioned measurement conducted by Kibédi et al. [Phys. Rev. Lett. 125, 182701 (2020)].

Method: For the primary experiment of this work the Hoyle state was populated by the ${}^{12}\mathrm{C}(p,p^{\prime })$ reaction at 10.8 MeV at the Oslo Cyclotron Laboratory. The $\gamma$-decay branching ratio was deduced through triple-coincidence events, each consisting of a proton-ejectile energy corresponding to population of the $0_2^{+}$ Hoyle state, and the subsequent cascade of 3.21 and 4.44 MeV $\gamma$ rays. To verify the analysis, a surrogate $\gamma$-ray cascade from the $0_2^{+}$ state in ${}^{28}\mathrm{Si}$ was also studied. Following the same methodology, an independent analysis of the 2014 data published by Kibédi et al. [Phys. Rev. Lett. 125, 182701 (2020)] was carried out.

Results: From the main experiment of this work, a $\gamma$-decay branching ratio of the Hoyle state was determined as ${\mathrm{\Gamma }}_{\gamma }^{7.65}/{\mathrm{\Gamma }}^{7.65}=4.0\left(3\right)\times {10}^{-4}$, yielding a radiative branching ratio of ${\mathrm{\Gamma }}_{\text{rad}}/\mathrm{\Gamma }=4.1\left(4\right)\times {10}^{-4}$. The independent reanalysis of the 2014 experiment published by Kibédi et al. [Phys. Rev. Lett. 125, 182701 (2020)] in this work yielded ${\mathrm{\Gamma }}_{\gamma }^{7.65}/{\mathrm{\Gamma }}^{7.65}=4.5\left(6\right)\times {10}^{-4}$, with a corresponding radiative branching ratio of ${\mathrm{\Gamma }}_{\text{rad}}/\mathrm{\Gamma }=4.6\left(6\right)\times {10}^{-4}$.

Conclusions: The radiative branching ratio of the Hoyle state reported in this work is in excellent agreement with several recent studies, as well as the previously adopted ENSDF average of ${\mathrm{\Gamma }}_{\text{rad}}/\mathrm{\Gamma }=4.16\left(11\right)\times {10}^{-4}$. In this work, several issues were found in the analysis of Kibédi et al. [Phys. Rev. Lett. 125, 182701 (2020)], with the corrected values no longer being discrepant with the ENSDF average.

Atomic nuclei undergo rapid changes in structure, often characterized as transitions between “spherical” and “deformed” shapes, with small changes in the number of protons or neutrons. While it has long been known that shell closures drive spherical shapes and residual proton-neutron interactions drive collective motion and deformation, detailed theoretical studies that show how this competition leads to rapid nuclear structural changes have been challenging. This is particularly true for the $Z=64$ subshell closure, which affects the low-lying spectra and electric quadrupole transition strengths of the xenon, barium, cerium, neodymium, samarium, and gadolinium isotopic chains. Using a particle-number-conserved BCS theory and angular-momentum projection, we provide the first consistent description of the nuclear shape evolution and quantum phase transition among these nuclides. In particular, we find that the quasi-SU(3) couplings of the proton $0h_{11/2}\text{−}1f_{7/2}$ orbitals and the neutron $0i_{13/2}\text{−}1g_{9/2}$ orbitals, which are outside the usual model space, play a crucial role in overcoming the robustness of the $Z=64$ shell gap and initiating phase transitions. The neutron coupling is also essential for the gradual evolution in the heavier barium isotopes.

The overlap function and the spectroscopic factor (SF) of $\alpha$-cluster and valence neutron in ${}^{12}\mathrm{Be}$ are calculated by the generator coordinates method (GCM) with the cluster model. By fixing the distance between the $\alpha$-clusters' generated coordinates, we make a theoretical experiment to analyze the relationship between the $\alpha$-clustering separation and the orbital occupation of the valence neutron in ${}^{12}\mathrm{Be}$. The analysis of the results shows that the percentage of the $\sigma$-orbital occupation in ${}^{12}\mathrm{Be}$ is positively related to the clustering separation.

Background: The nuclear shell model is a powerful framework for predicting nuclear structure observables, but relies on interaction matrix elements fit to experimental data as its inputs. Extending the shell model's applicability, particularly toward dripline nuclei, requires efficient fitting methods and credible uncertainty quantification. Traditional approaches face computational challenges and may underestimate uncertainties.

Purpose: We develop and test a framework combining eigenvector continuation and Markov chain Monte Carlo to efficiently fit shell model interaction matrix elements and quantify their uncertainties.

Methods: Eigenvector continuation is used to emulate shell model calculations, reducing computational costs. The emulator enables Markov chain Monte Carlo sampling to optimize interaction matrix elements and rigorously assess parametric uncertainties. The framework is benchmarked using the USDB interaction in the $sd$ shell.

Results: The emulator reproduces the USDB interaction with negligible error, validating its use in shell model fitting applications. However, we find that to obtain credible predictive intervals, the model defect of the shell model itself, rather than experimental or emulator error, must be taken into account in order to obtain credible uncertainties.

Conclusions: The proposed framework provides an efficient and rigorous approach for fitting shell model interactions and quantifying uncertainties. Further, the normality assumption used in the past appears sufficient to describe the distribution of interaction matrix elements. However, it is crucial to account for model correlations to avoid underestimating uncertainties.