The low-excitation states of atomic nuclei in the region around the $N=Z=28$ shell closure are generally well described by the shell model. Most experimental observables in the iron isotopes ${}^{56}\mathrm{Fe}$, ${}^{58}\mathrm{Fe}$, and ${}^{60}\mathrm{Fe}$ $(Z=26;$ $N=30, 32, 34)$ support a shell-model description. However, the lifetimes of the $4_1^{+}$ state in ${}^{58}\mathrm{Fe}$ in the literature result in a reduced transition strength that deviates markedly from shell-model predictions. There are three independent measurements, all in agreement and all based on the Doppler-shift attenuation method (DSAM) or Doppler-broadened line shape method (DBLS). In this work, Coulomb-excitation measurements were performed on ${}^{56}\mathrm{Fe}$ and ${}^{58}\mathrm{Fe}$ beams to determine the ratios $B(E2;4_1^{+}\to 2_1^{+})/B(E2;2_1^{+}\to 0_1^{+})$. Thus, $B(E2;4_1^{+}\to 2_1^{+})$ is determined relative to the known $B(E2;2_1^{+}\to 0_1^{+})$ values. For ${}^{56}\mathrm{Fe}$, $B(E2;4_1^{+}\to 2_1^{+})=23\left(4\right)\mathrm{W}.\mathrm{u}.$, agreeing with the adopted value. However, for ${}^{58}\mathrm{Fe}$, the $B(E2;4_1^{+}\to 2_1^{+})$ values obtained (for the various combinations of matrix element signs that could not be firmly established) are all significantly lower than the value derived from the previous lifetime measurements, and are in accord with shell-model calculations. The 1978 DSAM measurement of Bolotin et al. [Nucl. Phys. A 311, 75 (1978)] has been re-examined. The discrepancy between that measurement and the Coulomb-excitation measurement can be ascribed to the Lindhard-Scharff-Schiøtt (LSS) electronic stopping powers adopted for the DSAM analysis, which considerably overestimate contemporary values. Evidently, lifetime measurements from that era that are based on LSS stopping powers should be used with caution. The revised lifetime data, incorporating current stopping powers, are compared with shell-model calculations.

The first order chiral phase transition for quark matter with flavor imbalance is studied using the Linear $\sigma$ model with quarks, also known as quark-meson model. Special attention is paid to the role of the scalar isovector meson. The general consensus presently is that the chiral transition changes from a smooth crossover to first-order at low temperatures. This transition is assumed to be discontinuous with unstable or metastable intermediate states. However, if multiple charges are simultaneously conserved the system could undergo a continuous change through a coexistence of equilibrium states. Under such assumption the bulk properties are analyzed and several remarkable effects for the speed of sound and the susceptibilities are stressed.

Background: The São Paulo optical model protocol (SP-OMP) has been developed [Alvarez et al., Phys. Rev. C 100, 064602 (2019); Garrido-Gómez, Vegas-Díaz, Fernández-García, and Alvarez, ibid. 109, 054608 (2024); Garrido-Gómez et al., ibid. 112, 064602 (2025)] with the aim of establishing a common background to describe stable tightly and weakly bound nuclei reactions. This protocol consists of applying four optical model (OM) variants, based on the second version of the double-folding (DF) São Paulo potential (SPP2) [Chamon, Carlson, and Gasques, Comput. Phys. Commun. 267, 108061 (2021)], and the respective optical potentials (OP), to reproduce experimental nuclear-reaction data. The protocol includes a ${\chi }_{\text{red}}^2$ heat map that defines the correlation between real and imaginary OP strengths, their uncertainties, and the sensitivity of the data to them. The OP is applied to microscopic coupled-channel (CC) calculations.

Purpose: This work presents new experimental data for the elastic- and inelastic-scattering angular distributions of ${}^{12}\mathrm{C}+{}^{64}\mathrm{Zn}$, at bombarding energies near the Coulomb barrier ($V_B$ $\approx$ 30 MeV). Data were obtained at three bombarding energies: $E_{\text{lab}}=29.9$, 35.8, and 40.0 MeV. We perform and present the SP-OMP analysis and CC calculations.

Method: From the SP-OMP analysis, we determine the best-fit OPs. The OPs are then applied to the CC calculations. The theoretical OM analysis and CC calculations are compared to the experimental elastic- and inelastic-scattering angular distributions of ${}^{12}\mathrm{C}+{}^{64}\mathrm{Zn}$.

Results: The calculations provide an overall description of the data. The SP-OMP effectively describes the elastic-scattering cross sections of ${}^{12}\mathrm{C}+{}^{64}\mathrm{Zn}$. The CC calculations corroborate the OM analysis, highlighting the main importance of taking into account the first $2^{+}$ and $3^{-}$ excited states of the ${}^{64}\mathrm{Zn}$ target. In addition, we study the importance of coupling the first $2^{+}$ excited state of the ${}^{12}\mathrm{C}$ projectile, which shows to play an important role as the bombarding energy increases.

Conclusion: The application of SP-OMP analysis combined with microscopic CC calculations allows for a better and complementary understanding of the dynamics of ${}^{12}\mathrm{C}$ nuclear reactions as a function of the bombarding energy. The results should contribute to further discriminate between reactions with tightly and weakly bound stable nuclei.

The lattice QCD results for the temperature-dependent magnetic susceptibility of the medium below the crossover temperature cannot be reconciled with the widely used Hadron Resonance Gas model, also amended with the physical magnetic moments of hadrons or the pion–vector-meson loops. As noticed earlier, one observes a substantially too strong diamagnetism at temperatures in the range above $\approx 120\mathrm{MeV}$ compared to the lattice. This hints at a presence of quarks significantly below the QCD crossover temperature, which are needed as a source of paramagnetism. However, the pions must be retained to describe the diamagnetism data at low temperatures. Therefore, we consider here a quark-meson approach, where the temperature-dependent quark masses are fixed in a model-free way using the baryon-baryon and baryon-strangeness susceptibilities from the lattice at zero magnetic field. The constituent quarks possess anomalous magnetic moments estimated from the octet baryon magnetic moments. The vacuum quark-loop and meson-loop contributions are duly incorporated. We show that in such a framework, one can describe the magnetic susceptibility up to the crossover point. The qualitative conclusion is that the QCD degrees of freedom must extend far below the crossover temperature, down to $\approx 120\mathrm{MeV}$.

Based on chiral soliton models, the quantum fluctuation energies of quarks over a spatially inhomogeneous meson field background are thoroughly studied. We use a systematic calculation scheme initiated by Schwinger, in which the loop quantum fluctuation energies are evaluated by a nontrivial level summation over the eigenvalue spectrum of the effective Hamiltonian of the system. The effective Hamiltonian can be constructed by the one-loop effective action of fluctuations of quarks over a static chiral soliton field background. The corresponding Dirac equation is obtained. In a static and spatially spherical case and by the hedgehog ansatz the radial part and the angular part of the grand spin of the wave function for the Dirac equation can be separated. Due to the soliton background the eigenvalue spectrum is distorted. The scattering phase shift can be determined by solve the radial equations at different momentum. The density of states in momentum space can be derived. The effective Hamiltonian is diagonalized in a Hilbert space where the eigenfunctions are labeled by the parity, grand spin, and energy. The renormalization scheme can be carried out by a Born subtraction of the phase shift and the compensating Feynman diagram renormalization. Finally the finite quantum fluctuation energies over chiral soliton background at different parities and grand spins are numerically evaluated, compared, and discussed.

Lifetimes of several excited states in the mirror nuclei ${}^{47}\mathrm{Cr}\text{−}{}^{47}\mathrm{V}$ and ${}^{49}\mathrm{Mn}\text{−}{}^{49}\mathrm{Cr}$, located at the center of the $f_{7/2}$ shell, were measured using the advanced $\gamma$-ray tracking array AGATA. The Doppler shift attenuation method was employed to determine such lifetimes in the subpicosecond range. The reduced transition probabilities obtained from the lifetimes are compared to shell-model calculations in the full $fp$ space. The shell-model-calculated $B\left(E2\right)$ values were underestimated in comparison with experimental data. In particular, large discrepancies are obtained in ${}^{49}\mathrm{Mn}$ at low spin. These results suggest an incomplete understanding of low-energy states in the studied nuclei and call for further refinement of the existing nuclear structure theories.

Employing the five-dimensional collective Hamiltonian based on relativistic density functional theory, we investigate how the entanglement between collective shape and rotational degrees of freedom evolves along the even-even hafnium chain ${}^{154–198}\mathrm{Hf}$. Potential-energy surfaces, deformation parameters, and low-lying spectra delineate a coherent shape transition with distinct deformation characteristics. The entanglement entropy decreases monotonically as the nucleus departs from sphericity and locks into a stable prolate minimum, remains flat at maximal axial symmetry, then ascends anew with the resurgence of $\gamma$ softness and shape transition. A connection is established between the calculated entanglement entropy and the experimentally accessible $B\left(E2\right)$ ratio $R_B=B(E2,2_2^{+}\to 2_1^{+})/B(E2,2_1^{+}\to 0_1^{+})$, demonstrating the effectiveness of $R_B$ as a sensitive probe of the structural information encoded in the entanglement entropy.

Background: Complexity of deuteron-nucleus interactions—due to reactions induced by nucleons following weak binding-energy deuteron breakup (BU) and stripping and pickup direct reactions (DRs) in addition to statistical preequilibrium emission (PE) and evaporation from the compound nucleus (CN)—still motivates deuteron database updates and advanced deuteron activation analysis.

Purpose: New measurements of deuteron-induced charged-particle emission cross sections of ${}^{\mathrm{nat}}\mathrm{Mo}$ enhance the available data and improve understanding of BU, DR, PE, and CN reaction mechanisms.

Methods: Activation cross sections for ${}^{88,89}\mathrm{Zr}$, ${}^{88–92,95–98}\mathrm{Nb}$, and ${}^{90,91,93,99,101}\mathrm{Mo}$ residual nuclei in deuteron-induced reactions on Mo were measured by the stacked-foil technique and high-resolution gamma spectrometry using the U-120M cyclotron of the CANAM infrastructure of NPI CAS, at energies up to 20 MeV, and at the NFS SPIRAL2/GANIL facility at energies up to 40 MeV, where a single-foil technique and a dedicated transport system were used for short-lived isotopes. Their analysis included ${}^{91–97,99,101}\mathrm{Tc}$ activation, paying particular attention to BU and DR mechanisms too.

Results: The measured activation excitation functions enhance the available deuteron data for molybdenum, while concurrent analysis of all available data may improve their consistency.

Conclusions: Overall agreement of the calculated and measured cross sections, including the new data up to 40 MeV, establishes a suitable description of nuclear mechanisms involved within deuteron-induced reactions on Mo, especially the BU and DR processes. An improved analysis of the $\mathrm{CN}+\mathrm{PE}$ spin distribution effects can take advantage of the isomeric-state activation data in this work.

The development of nuclear reaction models for the production of evaluated nuclear data has traditionally been performed by comparing measured cross sections with predictions from reaction model codes whose physical input parameters are adjusted to obtain the best agreement between measured and modeled results. To more directly probe reaction model inputs, this work introduces a forward modeling approach to experimental reaction cross-section determination, where the most important physical input parameters to reaction model calculations are obtained via ${\chi }^2$ minimization between measured and calculated observables. This was demonstrated using data collected by the Gamma Energy Neutron Energy Spectrometer for Inelastic Scattering (GENESIS) at the 88-inch cyclotron at Lawrence Berkeley National Laboratory, a detection array consisting of organic liquid scintillators and high-purity germanium (HPGe) detectors. Using a broad-spectrum neutron beam and a $99.98\%$-enriched ${}^{56}\mathrm{Fe}$ target, GENESIS was used to perform a simultaneous measurement of ${}^{56}\mathrm{Fe} \gamma$-ray production cross sections and secondary neutron energy and angle distributions. The results of the forward modeling approach to the determination of energy-differential $\gamma$-ray production cross sections for the yrast $4^{+}\to 2^{+}$ and $6^{+}\to 4^{+}$ transitions, as well as eight other off-yrast transitions, were compared against those obtained using conventional techniques, and the results are in good agreement. In addition to discrete $\gamma$-ray yield total scattered neutron energy-angular distributions as a function of incident neutron energy were also obtained using forward modeling and found to agree with evaluated data, with the exception of elastic scattering at small angles. The fitted reaction model parameters obtained through forward modeling were also used to calculate the cross section for the unobserved $(n,2n)$ reaction; excellent agreement with the current evaluation was obtained, providing a validation of the predictive capabilities of the forward model approach. This work bridges the gap between nuclear data experiment and evaluation by providing a new means for extracting inelastic neutron-scattering cross sections and neutron-induced $\gamma$-ray production data while directly probing reaction model physics.

The density functional renormalization group is proposed to investigate the density fluctuations within the functional renormalization group approach, which allows us to quantify the medium effect and study physics of high densities. This method is applied to the nucleon-meson effective field theory, also known as the Walecka model, to study the properties of nuclear matter at high baryon densities. It is found that both the attractive and repulsive nucleon meson interactions are screened by the high-density medium, which results in a stiffer equation of state (EoS) of nuclear matter in the regime of ${\rho }_0\lesssim \rho \lesssim 2.5{\rho }_0$, then a softer EoS when $\rho \gtrsim 2.5{\rho }_0$. Here ${\rho }_0$ denotes the saturation baryon density of symmetric nuclear matter. Furthermore, a new phenomenon called the locking of Fermi surface is found. In the locking of Fermi surface the effective energy of quasinucleon is always close to the Fermi surface, which are both running with the renormalization group scale.

The neutron-proton-electron matter under a strong magnetic field is studied in the context of the covariant Vlasov approach. A covariant relativistic approach based on the Vlasov equation is applied to the study of infinite asymmetric magnetized nuclear matter. We use several relativistic mean-field nuclear models with nonlinear terms. The dispersion relations for the longitudinal modes are obtained, and the isovector and isoscalar collective modes are determined in a wide range of densities as a function of the isospin asymmetry, momentum transfer, and magnetic field. A strong magnetic field gives rise to the appearance of low-lying isovector modes that propagate in nuclear matter, not present in nonmagnetized matter. Neutron-like modes are essentially not affected by the presence of a strong magnetic field. In the presence of a strong magnetic field, Landau quantization modifies the proton-like collective modes, leading to the emergence of new branches associated with distinct Landau levels. These new modes can propagate even at high densities and exhibit isoscalar or isovector character.

Background: The quantum-number projected generator coordinate method (PGCM) has gained increasing attention, in part due to its combination with the in-medium similarity renormalization group (IMSRG) to describe collective excitations in medium-mass deformed nuclei, as well as nuclear matrix elements (NMEs) of neutrinoless double-$\beta$ ($0\nu \beta \beta$) decay.

Purpose: Extending the PGCM to Gamow-Teller (GT) transitions and two-neutrino double-$\beta$ ($2\nu \beta \beta$) decay is nontrivial, as it requires an accurate description of not only nuclear ground states but also a large number of excited states. In this work, we aim to achieve a minimal extension of the PGCM to describe GT transition strengths in even-even nuclei and to compute the NME of $2\nu \beta \beta$ decay.

Method: Within the PGCM framework, the wave functions of odd-odd nuclei are constructed as superpositions of neutron and proton quasiparticle configurations built on quasiparticle vacua constrained to have, on average, odd neutron and odd proton particle numbers. The angular momentum and particle numbers associated with the underlying mean-field states are restored through projection techniques. Using a shell-model Hamiltonian defined in the $fp$ shell, we assess the validity of this approach by benchmarking GT transitions in calcium and titanium isotopes, as well as the $2\nu \beta \beta$ decay of ${}^{48}\mathrm{Ca}$ to ${}^{48}\mathrm{Ti}$, against exact solutions. For comparison, we also confront our results with those obtained from configuration-interaction calculations employing different particle-hole truncation schemes, both with and without IMSRG evolution.

Results: The PGCM generally reproduces GT transitions to both low-lying and giant resonance states in ${}^{42–48}\mathrm{Ca}$ and ${}^{42–48}\mathrm{Ti}$. Although the agreement with exact results deteriorates as the number of valence nucleons increases, the overall description remains robust. The NME of the $2\nu \beta \beta$ decay from ${}^{48}\mathrm{Ca}$ to ${}^{48}\mathrm{Ti}$ is calculated without invoking the closure approximation. We find that the PGCM overestimates this matrix element by about 51%, primarily due to an overestimation of the GT transition strength from ${}^{48}\mathrm{Ti}$ to the first excited state of ${}^{48}\mathrm{Sc}$. Overall, the performance of the PGCM is comparable to, and in some cases exceeds, that of the CI calculation with the two-particle–two-hole truncation for the nuclei concerned.

Conclusions: The currently implemented PGCM framework provides a reliable description of GT transitions from even-even nuclei to low-lying states of odd-odd nuclei in regions not far from closed shells. As the number of valence nucleons increases, deviations from exact results become more noticeable, reflecting the growing importance of complex many-body correlations. These discrepancies are expected to be reduced by extending the set of generator coordinates and by incorporating the IMSRG evolution, which together offer a promising route toward further enhancing the predictive power of the PGCM framework.

We report the measurement of the ${}^{214}\mathrm{Bi}\beta$-decay spectrum to the ground state of ${}^{214}\mathrm{Po}$ using the XENONnT detector. This decay is classified as first-forbidden nonunique, for which theoretical predictions require detailed nuclear structure modeling. A dedicated identification algorithm isolates a high-purity sample of ground-state $\beta$ decays, explicitly excluding events with associated $\gamma$-ray emission. By comparing the measured spectrum, which covers energies up to $3.27\mathrm{MeV}$, with several nuclear models, we find that the prediction based on the conserved vector current hypothesis provides the best description of the data. Using this dataset, we additionally derive charge and light yield curves for electronic recoils, extending detector response modeling up to the megaelectronvolt scale.

This study explores the role of nucleon exchange for the generation of the fission fragment angular momenta. For a number of typical fission cases, samples of ${10}^4$ shape evolutions are generated by Langevin simulation and, subsequently, for each such evolution, the nucleon exchange transport theory previously developed for damped nuclear reactions is used to obtain the development of the fragment spin-spin distribution within the Fokker-Planck transport framework. The characteristic evolution of both parallel and perpendicular spin components is discussed. A common feature is that the rotational modes fall out of equilibrium before scission when the temperature rises rapidly while the concurrent shrinking of the neck suppresses further exchange. A number of fission observables are extracted from the event ensembles: the distribution of the magnitude of the fragment spin and its orientation relative to the fission axis, as well as the correlation between the two spins and the distribution of their opening angle. The dependence of these observables on the mass asymmetry is also examined.

Elliptic flow of deuterons is measured on simulated collision events of $\mathrm{Pb}+\mathrm{Pb}$ at CMS energy of 2.76 TeV per colliding nucleon pair. We use a hybrid model that includes hydrodynamics for the deconfined phase and hadron transport as an afterburner. For deuterons, two production mechanisms are examined: coalescence, and direct thermal production during hadronization and subsequent transport through the hadronic phase. Differential elliptic flow of deuterons in different centrality bins is evaluated for both implemented production models. In this approach, coalescence describes the experimental data better than direct deuteron production.

We present an approach for including relativistic corrections in lepton-nucleus scattering calculations within the short-time approximation (STA). Previous ab initio studies employed electromagnetic currents expanded in powers of $q/m$, where $q$ is the momentum transfer and $m$ is the nucleon mass, restricting their validity to low-$q$ kinematics. We adopt an expansion scheme that treats the initial nucleon momentum perturbatively while allowing for arbitrary momentum transfer, thereby extending the applicability of the STA to high-$q$ regimes. Additionally, we incorporate a relativistic treatment of the two-nucleon final-state energies. Calculations for ${}^3\mathrm{He}$ and ${}^4\mathrm{He}$ inclusive electron-scattering cross sections show a substantial improvement over previous results, achieving good agreement with experimental data in the quasi-elastic region for both low- and high-momentum transfer.

Nuclear $\beta$ decay is a key element of the astrophysical rapid neutron capture process ($r$ process). In this work, we present state-of-the-art global $\beta$-decay calculations based on the quantified relativistic nuclear energy density functional theory and the deformed proton-neutron quasiparticle random-phase approximation. Our analysis considers contributions from allowed and first-forbidden transitions. We used two point-coupling functionals with carefully calibrated time-odd terms and isoscalar pairing strength. The new calculations display consistent results for both employed functionals, especially near the neutron drip line, suggesting slower $\beta$ decays past the $N=126$ neutron shell closure than in commonly used $\beta$-decay models. The new rates, along with the existing rates based on the recent nonrelativistic global calculations, are found to slow down the synthesis of heavy elements in the $r$ process and significantly reduce the contribution of neutron-induced fission.

We extend the active learning emulators for two-body scattering in coordinate space with error estimation, recently developed by Maldonado et al. [Phys. Rev. C 112, 024002 (2025)], to coupled-channel scattering in momentum space. Our full-order model (FOM) solver is based on the Lippmann-Schwinger integral equation for the scattering $t$-matrix as opposed to the radial Schrödinger equation. We use (Petrov-)Galerkin projections and high-fidelity calculations at a few snapshots across the parameter space of the interaction to construct efficient reduced-order models (ROMs), trained by a greedy algorithm for locally optimal snapshot selection. Both the FOM solver and the corresponding ROMs are implemented efficiently in python using Google's jax library. We present results for emulating scattering phase shifts in coupled and uncoupled channels and cross sections, and assess the accuracy of the developed ROMs and their computational speedup factors. We also develop emulator error estimation for both the $t$-matrix and the total cross section. The software framework for reproducing and extending our results is publicly available. Together with our recent advances in developing active learning emulators for three-body scattering, these emulator frameworks set the stage for full Bayesian calibrations of chiral nuclear interactions and optical models against scattering data with quantified emulator errors.