Using the time-of-flight technique, we measured the beta-delayed neutron emission of ${}^{132}\mathrm{Cd}$. From our large-scale shell model (LSSM) calculation using the ${\mathrm{N}}^3\mathrm{LO}$ interaction [, 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 ${}^{132}\mathrm{Cd}$ decay data presented here, offers robust predictive power for nuclei of astrophysical interest such as $r$-process waiting points.

Tetrahedral symmetry has long been predicted as an exotic shape degree of freedom in atomic nuclei, yet clear experimental manifestations remain elusive. We show that the triple binding energy difference $\delta V_{pn}^{(3)}$ can isolate a structural effect of tetrahedral symmetry in ${}^{80}\mathrm{Zr}$. Using relativistic density functional theory solved on a three-dimensional lattice without symmetry restrictions, the experimental $\delta V_{pn}^{(3)}$ values for even-even ${}^{80-90}\mathrm{Zr}$ isotopes are well reproduced without adjustable parameters. While an enhancement of $\delta V_{pn}^{(3)}$ near $N\simeq Z$ is commonly attributed to proton-neutron correlations beyond the mean field, the pronounced nonmonotonic peak at $N=40$ emerges at the mean field level only when the tetrahedral degree of freedom is included. Constraining the tetrahedral deformation to zero removes the peak and leads to clear deviations from experiment. The anomaly is traced to a well-localized tetrahedral minimum in ${}^{80}\mathrm{Zr}$, supported by potential energy surfaces and characteristic single-particle level splittings. Calculations restricted to quadrupole and triaxial shapes fail to reproduce the localized enhancement, indicating that the effect is not a generic proton-neutron correlation but a symmetry-selective increase of proton-neutron binding associated with tetrahedral geometry. We, therefore, identify the $\delta V_{pn}^{(3)}$ anomaly in ${}^{80}\mathrm{Zr}$ as a structural mechanism distinct from the conventional Wigner-type enhancement and show that nuclear masses constitute a sensitive probe of tetrahedral symmetry.

Nuclear mass is a key indicator of how the nuclear shell structure evolves. The recent mass measurement study of neutron-rich lanthanum isotopes [Jaries et al., Phys. Rev. Lett. 134, 042501 (2025)] reveals the presence of a distinct prominence in their two-neutron separation energies. However, its presence has been called into question based on the results of another mass determination [Liu, Ph.D. thesis, University of Notre Dame, 2025, 10.7274/28766600.v1.]. In this Letter, we report an effort to clarify these contradictory results through the use of the simultaneous mass-lifetime measurement of the neutron-rich lanthanum isotope ${}^{149}\mathrm{La}$ using a multireflection time-of-flight mass spectrograph combined with a $\beta$-TOF detector. The peak corresponding to a $\beta$-decaying state was observed in the time-of-flight spectra at a position of $221(6)\mathrm{keV}/{\mathrm{c}}^2$ lighter than the reported ${}^{149}\mathrm{La}$ mass in Jaries et al., but our measured result is in excellent agreement with the mass value reported in Liu. We have concluded that this peak is the ground state of ${}^{149}\mathrm{La}$. With this, the previously reported distinct prominence in the two-neutron separation energies disappears, while a new kink structure, similar to that in the cerium isotopes, appears. Comparison with theoretical models suggests that a nuclear shape transition from octupole deformation to another type of deformation occurs around $N=91$ and is likely the cause of this kink structure.

EXO-200 was a leading double beta decay experiment consisting of a single-phase, enriched liquid xenon time projection chamber filled with an admixture of 80.672% ${}^{136}\mathrm{Xe}$ and 19.098% ${}^{134}\mathrm{Xe}$. The detector operated at the Waste Isolation Pilot Plant between 2010 and 2018 and was designed to search for double beta decay of ${}^{136}\mathrm{Xe}$. Data were acquired in two phases separated by a period of detector upgrades. We report on the search for $0\nu \beta \beta$ and $2\nu \beta \beta$ decay of ${}^{134}\mathrm{Xe}$ with Phase II EXO-200 data, with median 90% CL exclusion sensitivity to half-life $T_{1/2}^{0\nu }\ge 3.7\times {10}^{23}\mathrm{yr}$ and $T_{1/2}^{2\nu }\ge 2.6\times {10}^{21}\mathrm{yr}$, respectively. No statistically significant signal is observed for either decay mode. We set a world-leading lower limit on the half-life of the neutrinoless decay mode of ${}^{134}\mathrm{Xe}$ of $T_{1/2}^{0\nu }\ge 8.7\times {10}^{23}$ (90% CL) and the second strongest constraint on the two-neutrino decay of $T_{1/2}^{2\nu }\ge 2.9\times {10}^{21}$ (90% CL), a threefold improvement over the EXO-200 Phase I measurement. New constraints are also set for the $2\nu \beta \beta$ and $0\nu \beta \beta$ decays of ${}^{134}\mathrm{Xe}$ to the lowest excited state of ${}^{134}\mathrm{Ba}$.

Experimental observations of the low-lying states in ${}^{12}\mathrm{Be}$ and their accurate modeling play an essential role in understanding the disappearance of the $N=8$ magic number. Long-standing experimental ambiguities have been clarified using an one-neutron adding ($d$, $p$) reaction on ${}^{11}\mathrm{Be}$ using the ISOLDE Solenoidal Spectrometer at CERN’s HIE-ISOLDE facility. The single-particle energies of $1s_{1/2}$, $0d_{5/2}$, and $0p_{1/2}$ orbitals in ${}^{12}\mathrm{Be}$ have been determined from the extracted spectroscopic factors. A significant reduction between the separation of $1s_{1/2}$ and $0p_{1/2}$ orbitals is found in comparison with the carbon isotones, highlighting the breakdown of the $N=8$ shell. These observations serve as an important test of different effects incorporated in theoretical models. It is found that two synergistic mechanisms, core deformation and weak binding, are responsible for the $N=8$ shell breaking and the exotic near-threshold phenomena observed in ${}^{12}\mathrm{Be}$, including the narrow unnatural-parity resonance $0_1^{-}$ and the possible halolike nature of the $0_2^{+}$ isomer.

In the last decades, femtoscopic measurements from heavy-ion collisions have become a popular tool to investigate the strong interactions between hadrons. The key observables measured in such experiments are the two-hadron momentum correlations, which depend on the production mechanism of hadron pairs and the final-state interactions. Given the complexity of ultrarelativistic collision experiments, the source term describing the production mechanism can be modeled phenomenologically only based on numerous assumptions. The commonly employed approach for analyzing femtoscopic data relies on the Koonin-Pratt formula, which relates the measured correlation functions with the relative wave function of an outgoing hadron pair and a source term that is assumed to be universal. Here, we critically examine this universality assumption and show that, for strongly interacting particles such as nucleons, the interpretation of femtoscopic measurements suffers from a potentially large intrinsic uncertainty. We also comment on the ongoing efforts to explore three-body interactions using this experimental technique.

We introduce the $p_T$-differential radial flow $v_0(p_T)$ in the heavy-quark sector. Within an event-by-event Langevin framework, we show that this observable exhibits a strong sensitivity to the heavy quark-bulk interaction. It provides a powerful and novel tool to constrain the transport coefficients of heavy quarks in the quark-gluon plasma and, more generally, to assess the strength of the interaction of a Brownian particle in an expanding bulk medium. The results further indicate that heavy quarks exhibit collective behavior driven by the isotropic expansion of the quark-gluon plasma in heavy-ion collisions and, at low $p_T$, it offers a marked signature of the heavy-quark hadronization mechanism.

The photodisintegration cross sections of the deuteron have been systematically measured over the photon energy range of 2.33–19.65 MeV at the Shanghai Laser Electron Gamma Source. By applying the well-established Baldin sum rule to the newly obtained data, the sum of the electric and magnetic dipole polarizabilities of the deuteron is extracted for the first time based solely on a dense and continuous experimental dataset, yielding ${\alpha }_E+{\beta }_M=0.719\pm 0.009_{\mathrm{stat}}\pm 0.014_{\mathrm{algo}}\pm 0.023_{\mathrm{syst}}{\mathrm{fm}}^3$. With theoretical values of the magnetic polarizability ${\beta }_M$ calculated from the pionless effective field theory, a new value of the electric polarizability is obtained as ${\alpha }_E=0.637\pm 0.009_{\mathrm{stat}}\pm 0.014_{\mathrm{algo}}\pm 0.023_{\mathrm{syst}}\pm 0.004_{\mathrm{theo}}{\mathrm{fm}}^3$, which is in excellent agreement with current theoretical predictions. This result resolves the previous discrepancy between experimental measurements from elastic scattering and theory, providing a high-precision benchmark for nuclear interaction models.

We report the decisive resolution of the ground state spin and parity of the proton–drip line nucleus ${}^{22}\mathrm{Al}$, a prime candidate for a proton halo. The resolution stems from the first $\beta$-delayed charged particle emission experiment in the gas stopping area at the Facility for Rare Isotope Beams (FRIB), leveraging high-intensity, low-energy beams extracted from the Advanced Cryogenic Gas Stopper (ACGS). The pristine beam quality from FRIB and the ACGS enabled a sensitive particle identification technique using thin silicon detectors, allowing for the suppression of the dominant proton background and the first observation of the weak $\beta$-delayed $\alpha$ transition from the isobaric analog state in ${}^{22}\mathrm{Mg}$ to the ${}^{18}\mathrm{Ne}$ ground state. This observation uniquely fixes the ${}^{22}\mathrm{Al}$ ground state as $4^{+}$. The valence proton is confined by a dominant $d$-wave centrifugal barrier which, combined with the Coulomb repulsion, hinders the tunneling required for halo formation despite the exceptionally low proton separation energy of ${}^{22}\mathrm{Al}$.

Constructing fast and accurate surrogate models is a key ingredient for making robust predictions in many topics. We introduce a new model, the multiparameter eigenvalue problem (MEP) emulator. The new method connects emulators and can make predictions directly from observables to observables. We show that the MEP emulator can be trained with data from eigenvector continuation and parametric matrix model emulators. A simple simulation on a one-dimensional lattice confirms the performance of the MEP emulator. Using ${}^{28}\mathrm{O}$ as an example, we also demonstrate that the predictive probability distribution of the target observables can be straightforwardly obtained through the new emulator.

Experiments using intermediate- to high-energy radioactive nuclear beams present numerous findings. Extracting important properties of physical observables relies on a firm theoretical analysis. Though Glauber theory is believed to work well, no convincing calculation has so far been done. We perform Glauber-theory calculations of both elastic differential cross sections and total reaction cross sections for $p+{}^{12}\mathrm{C}$, ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$, and ${}^6\mathrm{He}+{}^{12}\mathrm{C}$ systems. The wave functions of both ${}^6\mathrm{He}$ and ${}^{12}\mathrm{C}$ are generated by variational Monte Carlo calculations with spatial and spin-isospin correlations induced by realistic two- and three-nucleon potentials. Glauber’s phase-shift function is computed by Monte Carlo integration up to all orders of nucleon-nucleon multiple scatterings. We show an excellent performance of the Glauber description to the selected data on the above systems. We also find that the cumulant expansion of the phase-shift function converges rapidly up to the second order for the above systems. This finding will open up interesting applications for the analysis of high-energy nuclear experiments.

We report on high-resolution laser spectroscopy of ${}^{255}\mathrm{Fm}$ ($T_{1/2}=20\mathrm{h}$), one of the heaviest nuclides available from reactor breeding. The hyperfine structures in two different atomic ground-state transitions at 398.4 nm and 398.2 nm were probed by in-source laser spectroscopy at the RISIKO mass separator in Mainz, using the perpendicularly illuminated laser ion source and trap (PI-LIST) high-resolution ion source. Experimental results were combined with hyperfine fields from various atomic ab initio calculations, in particular using multiconfiguration Dirac-Hartree-Fock theory, as implemented in grasp18. In this manner, the nuclear magnetic dipole and electric quadrupole moments were derived to be $\mu =-0.75(5){\mu }_{\mathrm{N}}$ and $Q_{\mathrm{s}}=+5.84(13)\mathrm{eb}$, respectively. The magnetic moment indicates occupation of the $\nu 7/2[613]$ Nilsson orbital, while the large quadrupole moment confirms strong, stable prolate deformation consistent with systematics in the heavy actinides. Comparisons with available expectation values from nuclear theory show good agreement, providing a stringent benchmark for the used theoretical models. These results revise earlier data and establish ${}^{255}\mathrm{Fm}$ as a reference isotope for future high-resolution studies.

We derive a formulation of relativistic spin hydrodynamics with totally antisymmetric spin tensors that satisfy the Frenkel-Mathisson-Pirani condition. In our proposed spin hydrodynamics, the second law of thermodynamics is fulfilled by the spin-induced corrections in the heat flow, the viscous tensor, and the antisymmetric part of the energy-momentum tensor. These corrections are interpreted as the inverse spin Hall effect and the anomalous Hall effect in the nonrelativistic limit. We show that our evolution equation for the spin density is interpreted as an extension of the Bargmann-Michel-Telegdi equation known in relativistic many-body systems, including the Thomas precession term, the spin-rotation term, and new coupling terms between spin and hydrodynamic variables.

$\beta$-decay rates of extreme neutron-rich nuclei remain largely unknown experimentally, while they are critical inputs for $r$-process nucleosynthesis. We present first ab initio calculations of total $\beta$-decay half-lives, with a focus on $N=50$ nuclei. Starting from nuclear forces and currents based on chiral effective field theory, we use the in-medium similarity renormalization group to consistently derive valence-space Hamiltonians and weak operators, from which we calculate the nuclear states involved and the Gamow-Teller transition strengths, without phenomenological adjustments. In addition, we explore effects of first-forbidden contributions. Our results show that the inclusion of two-body currents increases the total half-lives, which then show good agreement with the existing experimental data, thereby validating the predictive capability of our approach.

Although light nuclear clusters are known to form abundantly in warm and dilute nuclear matter, their role in hot and dense nuclear matter remains unclear due to the lack of experimental indication for their modifications by the Mott effect under such conditions. To address this issue, we resort to intermediate-energy heavy-ion collisions, where light clusters are mainly produced in the transiently formed hot and dense matter. A kinetic approach, which includes dynamically the formation and dissociation of light clusters, is employed to deduce the strength of the Mott effect and the $\alpha$-particle fraction in hot and dense nuclear matter from the light-nuclei yields measured by the FOPI Collaboration in central $\mathrm{Au}+\mathrm{Au}$ collisions at energies of $0.25A$ to $0.6A\mathrm{GeV}$. We find an unexpectedly abundant $\alpha$ clustering in this environment, which will have profound implications for modeling the nuclear equation of state and describing supernovae and neutron star mergers.

The weak binding and spatially extended neutron densities characteristic of drip-line nuclei give rise to a distinctive low-energy dipole response. The drip-line nucleus ${}^8\mathrm{He}$ is the most neutron-rich bound nucleus with a mass-to-charge ratio of $A/Z=4$. We measure the dipole response of ${}^8\mathrm{He}$, including for the first time the four-neutron decay channel. A total dipole strength of $\sum B(E1)(E^{*}<15\mathrm{MeV})=0.95(16)e^2{\mathrm{fm}}^2$ and a dipole polarizability of ${\alpha }_D=0.61(1){\mathrm{fm}}^3$ are extracted from the differential Coulomb-excitation cross section and compared to state-of-the-art theoretical calculations employing coupled cluster and three-body approaches. We find that the dipole continuum is dominated, even at high excitation energies well above the $4n$ decay threshold, by two-neutron emission, pointing to a ${}^6\mathrm{He}+2n$ structure of the excited dipole mode. No indication was found for a $4n$ final-state correlation, while pronounced $nn$ and ${}^6\mathrm{He}\text{−}n$ final-state correlations are apparent.

Finding high-quality trial wave functions for quantum Monte Carlo calculations of light nuclei requires a strong intuition for modeling the interparticle correlations as well as large computational resources for exploring the space of variational parameters. Moreover, for systems with three-body interactions, the wave function should account for many-body effects beyond simple pairwise correlations. In this Letter, we design neural networks that efficiently incorporate these factors to generate expressive wave function Ansätze for light nuclei using variational Monte Carlo. Our neural-network approach for $A=3$ nuclei can capture, already at the level of variational Monte Carlo, the overwhelming majority of the ground-state energy estimated by Green’s function Monte Carlo (GFMC). It achieves a ground-state energy within 0.45% of the GFMC result for ${}^3\mathrm{H}$ using the softest chiral interaction, representing a substantial improvement over standard variational Monte Carlo, which exhibits a 3.7% deviation. The result indicates the potential of neural networks to construct effective trial wave functions for quantum Monte Carlo calculations.

The simultaneous emission of two $\alpha$ particles—double-$\alpha$ decay—represents a long-predicted but unobserved mode of nuclear radioactivity. Here, we formulate this process as a genuine three-body problem within the hyperspherical coordinate framework and evaluate decay probabilities by numerically solving the corresponding hyperradial Schrödinger equation combined with large-scale random sampling of the potential parameters. Inspired by this, we demonstrate that the decay width ratio between simultaneous and sequential $\alpha$ emission exhibits a strikingly linear dependence on $Z{Q}_{\alpha \alpha }^{-1/2}$, extending the barrier penetration dynamics into the correlated few-body regime. The nuclei ${}^{108}\mathrm{Xe}$, ${}^{218}\mathrm{Ra}$, ${}^{224}\mathrm{Pu}$, ${}^{222}\mathrm{U}$, ${}^{216}\mathrm{Rn}$, and ${}^{220}\mathrm{Th}$ are suggested as the most promising candidates for the observation of double-$\alpha$ decay, with predicted half-lives potentially accessible within present detection limits. Our results provide a unified framework for multi-$\alpha$ decay and open a pathway to probing nuclear clustering and few-body correlations in heavy nuclei.