The present study aims at further development of covariant energy density functionals (CEDFs) towards more accurate description of binding energies across the nuclear chart. Infinite basis corrections to binding energies in the fermionic and bosonic sectors of the covariant density functional theory are taken into account in the fitting protocol within the covariant density functional theory. In addition, total electron binding energies are used in the conversion of atomic binding energies into nuclear ones. Their dependence on neutron excess is investigated across the nuclear chart within the atomic approach. These factors were disregarded in the previous generation of covariant energy density functionals, but their omission leads to substantial global calculation errors for physical quantities of interest. For example, these errors for binding energies are of the order of 0.8 MeV or higher for the three major classes of covariant energy density functionals.

The neutron-proton effective mass splitting ($\mathrm{\Delta }{m}_{np}^{*}$) is investigated through analyses of heavy-ion collisions using the improved quantum molecular dynamics model with both standard and extended Skyrme interactions. By uncovering the strong correlation between the slope of the neutron-to-proton yield ratio with respect to the kinetic energy (i.e., $S_{n/p}$) and $\mathrm{\Delta }{m}_{np}^{*}$, we reveal that the constraints of the neutron-proton effective mass splitting via heavy ion collisions depend on the kinetic energy region of the emitted nucleons. At low kinetic energies, the data favor $m_n^{*}>m_p^{*}$ which is consistent with the nucleon-nucleus scattering analysis, while at high kinetic energies, they favor $m_n^{*}<m_p^{*}$. Our findings partly resolve the longstanding discrepancy in the constraints of neutron-proton effective mass splitting with heavy ion collisions and nucleon-nucleus scattering, and significantly advance the understanding of nucleon effective mass splitting through heavy ion collisions.

Modeling lepton-nucleus scattering with the accuracy required to extract neutrino-oscillation parameters from long- and short-baseline experiments necessitates retaining most quantum-mechanical effects. One such effect is the interference between one- and two-body current operators in the transition currents, which has been known to enhance the cross sections, especially in transverse kinematics. In this work, we incorporate such interference in the spectral function formalism, which combines relativistic currents and kinematics with an accurate description of the initial target state. Our analysis of lepton-scattering off ${}^{12}\mathrm{C}$ demonstrates that interference effects appreciably enhance the transverse electromagnetic response functions and the flux-folded neutrino-nucleus cross section, in both cases, improving the agreement with experimental data. We discuss the impact on the neutrino-oscillation program and the determination of nucleon axial form factors.

We propose an optimized histogram binning strategy to reconstruct nuclear response functions via the Chebyshev expansion bound-state method. Our approach employs a stochastic regularization of the density of states to define adaptive, equal-area bins. Using the deuteron solved in a harmonic-oscillator basis with a chiral interaction, we benchmark on dipole and longitudinal responses, obtaining excellent agreement with exact theory and experiment. This general framework readily extends to other many-body systems and opens the door to new ab initio calculations of lepton-nucleus cross sections in medium-mass nuclei.

The E1 strength function is calculated over the entire nuclear chart using the axially deformed covariant quasiparticle finite amplitude method (QFAM). A zero-range effective interaction is used, and the numerical parameters of the calculations are optimized, allowing for the calculation of high-energy modes. A procedure to extract the quasiparticle random-phase approximation (QRPA) matrixlike spectrum from the QFAM strength function is established. The centroids and the width of the excited states are corrected by a phenomenological prescription to take into account missing correlations. The comparison to the experimental data shows a good description of the photodisintegration cross sections (including those of light nuclei), as well as average resonance capture and $(p,p^{\prime })$ ones. Overall, the present calculations provide excellent agreement with the data. Our results are compared to other systematic E1 strength function calculations based on the deformed Gogny QRPA or the fully phenomenological Lorentzian-type approaches. As an application, the present approach is used to describe the propagation of an extra-Galactic ${}^{56}\mathrm{Fe}$ source, in the framework of the interaction of ultra-high-energy cosmic rays with the cosmic microwave background. The average mass number during the propagation is found to be larger than the one resulting from the E1 strength function calculated with the Gogny functional but close to the one based on the phenomenological parametrization of the E1 strength function.

Nuclear fission can be modeled as a quantum tunneling process driven by the interplay between the nuclear binding energy and the collective inertia. Within the Wentzel-Kramers-Brillouin formalism, spontaneous fission half-lives can be obtained by minimizing the action integral in the multidimensional space of collective degrees of freedom. Hence, including the relevant collective variables is crucial for properly describing spontaneous fission probabilities. Pairing correlations play an essential role in this evaluation since the collective inertia decreases as the inverse of the square of the pairing gap and, therefore, they should be considered as a relevant degree of freedom on the same footing as deformation parameters. In this work, we show that the spontaneous fission half-lives in fermium isotopes can be reproduced in a microscopic theory by considering the least-action fission path in a two-dimensional space with constraints on the quadrupole moment and pairing correlations. We consider two microscopic quantities as degrees of freedom associated with pairing: the pairing-gap parameter $\mathrm{\Delta }$, and the particle-number fluctuations $\langle \mathrm{\Delta }{N}^2\rangle$. Least-action paths, computed using the Dijkstra algorithm, are compared with minimum-energy paths, highlighting the importance of pairing correlations as a dynamical degree of freedom.

Measurements of neutron elastic and inelastic scattering on ${}^{56}\mathrm{Fe}$ were performed at the Geel Electron Linear Accelerator (GELINA) of the EC-JRC. A highly enriched ${}^{56}\mathrm{Fe}$ scattering sample was used to minimize the contribution of minor iron isotopes, ensuring the extraction of precise scattering cross-section data. The time-of-flight technique was utilized to determine the neutron incident energies, with scattered neutrons detected using the ELastic and Inelastic Scattering Array (ELISA), consisting of 32 liquid organic scintillators capable of neutron-photon discrimination via pulse-shape analysis, while a ${}^{235}\mathrm{U}$ fission chamber was used to monitor the neutron fluence. The detectors are arranged into four arms, each comprising eight detectors at fixed angular positions relative to the neutron beam direction, facilitating the computation of both the angular distributions and the integral cross sections with the Gauss-Legendre quadrature. For elastic scattering, angular distributions, integral cross sections, and Legendre coefficients were determined across the energy range of 1 to 8 MeV. In the case of inelastic scattering, partial differential and angle-integrated cross sections from the first and the second excited states of ${}^{56}\mathrm{Fe}$ were extracted in the energy regions from 2 to 5 MeV and from 3 to 6 MeV, respectively. Additionally, the total cross section was estimated in the energy interval from 2 to 2.5 MeV. The results of this work were compared with available experimental data, the most recent evaluated nuclear data libraries, and theoretical calculations performed using the talys 1.9 code.

${}^{15}\mathrm{N}(p,\gamma ){}^{16}\mathrm{O}$ is one of the key reactions in the CNO cycle, which provides a link between the CN cycle and the CNO bi-cycle and determines the production of isotopes of elements such as oxygen and fluorine. Its cross sections at stellar energies are dominated by two broad $J^{\pi }=1^{-}$ resonances and the interferences between two resonances with the direct capture to the ground state, thus the proton asymptotic normalization coefficient (ANC) for the ground state in ${}^{16}\mathrm{O}$ has a significant impact on the $R$-matrix analysis for the astrophysical $S$ factor and even the determination of resonance parameters for the two $J^{\pi }=1^{-}$ states. In this work, the angular distribution of ${}^{15}\mathrm{N}({}^7\mathrm{Li},{}^6\mathrm{He}){}^{16}\mathrm{O}$ at $E_{\mathrm{lab}}=44\mathrm{MeV}$ was measured for the first time, the proton ANC for the ground state in ${}^{16}\mathrm{O}$ has been revised to be $13.24\pm 0.67{\mathrm{fm}}^{-1/2}$, and the parameters of two $1^{-}$ resonance and the astrophysical $S$ factor at zero energy have been updated based on the $R$-matrix analysis.

The symmetric ${}^{10}\mathrm{B}+{}^{10}\mathrm{B}$ reaction provides a unique opportunity to populate high-energy, high-spin states in the mirror pairs ${}^{10}\mathrm{Be}\text{−}{}^{10}\mathrm{C}$, ${}^{11}\mathrm{B}\text{−}{}^{11}\mathrm{C}$, and ${}^9\mathrm{Be}\text{−}{}^9\mathrm{B}$. Excitation spectra for these systems have been measured and mirror analog states identified, enabling a systematic comparison of their level energies. We find that states in compact shell-model configurations (e.g., members of ground-state rotational bands) show very small mirror energy differences (consistent with standard Coulomb displacement energies), whereas spatially extended clusterlike states exhibit significantly reduced energy gaps consistent with the Thomas-Ehrman shift. In the ${}^{10}\mathrm{Be}\text{−}{}^{10}\mathrm{C}$ pair, a previously unreported level at $E_x=9.24\mathrm{MeV}$ in ${}^{10}\mathrm{C}$ is observed, which we propose as the isospin analog of the 9.56 MeV $2^{+}$ state in ${}^{10}\mathrm{Be}$. In the ${}^{11}\mathrm{B}\text{−}{}^{11}\mathrm{C}$ pair, we report a high-lying state at $E_x=10.69\mathrm{MeV}$ in ${}^{11}\mathrm{C}$, mirroring the 11.21-MeV level in ${}^{11}\mathrm{B}$ which was populated via one-nucleon transfer for the first time. Finally, the observed ${}^9\mathrm{Be}\text{−}{}^9\mathrm{B}$ mirrors show nearly identical excitation spectra; in particular, strongly populated states follow a $J(J+1)$ energy trend, highest of which are consistent with their assignment as the $9/2^{-}$ members of the ground-state rotational band. These findings highlight the interplay of Coulomb and structural effects in mirror nuclei and extend the known level schemes of the nuclei in question.

Inspired by the recent debate as to whether the proton drip-line nucleus ${}^{22}\mathrm{Al}$ demonstrates a halo structure in its ground state, we have analyzed theoretical results for ${}^{22}\mathrm{Al}$ and a number of neighboring nuclei especially along isotopic, isotonic, and isobaric chains. Two state-of-the-art nuclear models, the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) and its extension in triaxial deformation (TRHBc), are used, where the effects of pairing, deformation, and the continuum are included self-consistently. Although the valence proton of the ${}^{22}\mathrm{Al}$ nucleus is found very loosely bound, in concordance with experimental data, its spatial distribution is found to hardly penetrate the potential barrier. Its wave function is found to consist predominately of $\ell =2$ components, for which halo formation is disfavored. Comparisons with results for isobars reveal a somewhat more extended density distribution than those of the stable or neutron-rich counterparts, but comparisons along isotopic, isotonic, and isobaric chains reveal no discontinuities in size evolution, which, if present, might have signaled exotic structures. The combined theoretical analysis of spatial distributions and binding employed in this work can be applied to explore other proton-halo candidates and their neighbors as proton drip-line nuclei become more and more accessible experimentally for detailed studies.

We explore the use of deep learning techniques to learn how nuclear cross sections change as we add or remove protons and neutrons. As a proof of principle, we focus on the neutron-induced reactions in the fast energy regime. Our approach follows a two-stage learning framework. First, we apply representation learning to encode cross section data into a latent space using either variational autoencoders (VAEs) or implicit neural representations (INRs). Then, we train graph neural networks (GNNs) on the resulting embeddings to predict missing values across the nuclear chart by leveraging the topological structure of neighboring isotopes. We demonstrate accurate cross section predictions within a $9\times 9$ block of missing nuclei. We also find that the optimal GNN training strategy depends on the type of latent representation used, with VAE embeddings performing best under end-to-end optimization in the original space, while INR embeddings achieve better results when the GNN is trained only in the latent space. Furthermore, using clustering algorithms, we map groups of latent vectors into regions of the nuclear chart and show that VAEs and INRs can discover some of the neutron magic numbers. These findings suggest that deep-learning models based on the representation encoding of cross sections combined with graph neural networks hold significant potential in augmenting nuclear theory models, e.g., by providing reliable estimates of covariances of cross sections, including cross-material covariances.

The alpha optical model potential ($\alpha$-OMP ) is a phenomenological approach used to describe elastic scattering where multiple reaction channels are open. It is one of the most critical inputs for the calculation of thermonuclear reaction rates in explosive stellar environments, but uncertainties within the $\alpha$-OMP lead to imprecise predictions hindering comparisons between calculations and observations. In order to improve the precision of the $\alpha$-OMP, additional nuclear physics data are required. In this paper, a measurement of the ${}^{86}\mathrm{Sr}(\alpha$, $\alpha )$ elastic scattering cross section at multiple energies is reported. A local optical potential is constructed via a fully Bayesian analysis of the elastic scattering data. The resulting uncertainties on the low-energy cross sections relevant to nuclear astrophysics are then calculated and shown to be on the order of $50\%$.

A microscopic investigation of the rotational properties in ${}^{129}\mathrm{Cs}$ and ${}^{131}\mathrm{La}$ was carried out using the three-dimensional tilted axis cranking covariant density-functional theory (3DTAC-CDFT). The calculations reveal the coexistence of magnetic and chiral rotation built on the same quasiparticle configurations $\pi h_{11/2}^1\otimes \nu h_{11/2}^{-2}$ in ${}^{129}\mathrm{Cs}$ and ${}^{131}\mathrm{La}$, establishing a new type of shape coexistence. The calculations predict the deformation parameters for magnetic rotation in ${}^{129}\mathrm{Cs}$ ($\beta \approx 0.23, \gamma \approx {41}^{\circ }$) and ${}^{131}\mathrm{La}$ ($\beta \approx 0.25, \gamma \approx {42}^{\circ }$), along with those for possible chiral rotation in ${}^{129}\mathrm{Cs}$ ($\beta \approx 0.20, \gamma \approx {29}^{\circ }$) and in ${}^{131}\mathrm{La}$ ($\beta \approx 0.20, \gamma \approx {27}^{\circ }$). The energy spectra, the relationship between the spin and the rotational frequency, and the reduced $M1$ and $E2$ transition probabilities are obtained for various configurations. The experimental characteristics of band B8 in ${}^{129}\mathrm{Cs}$ and band 13 in ${}^{131}\mathrm{La}$ are reasonably reproduced. Moreover, a distinctive rotational-mode transition is uncovered in this work, progressing from principal-axis rotation to planar rotation and finally to chiral rotation as the rotational frequency evolves through different regimes.

The state-of-the-art ab initio nuclear many-body approaches with modern nuclear forces are challenged by the recent experimental measurement of the monopole form factor of the $0_1^{+}\to 0_2^{+}$ transition in the $\alpha$ particle [Kegel et al., Phys. Rev. Lett. 130, 152502 (2023)]. We investigate the elastic and inelastic $0_1^{+}\to 0_2^{+}$ transition form factors using the ab initio no-core shell model (NCSM). We observe a good convergence of both form factors with respect to the basis size employing the Daejeon16 nucleon-nucleon ($NN$) interaction. Our NCSM results are very close to the effective interaction hyperspherical harmonic calculations using $NN$ plus three-nucleon interactions based on the chiral effective field theory which take into account the continuum effects via the Lorentz integral transform. The significant difference between the ab initio results with various modern nuclear interactions and of some of them with the recent experimental data provides motivations for deeper investigation of this observable.

Charge radii can be used as sensitive indicators to encode information about nuclear structure phenomena, and are influenced by various mechanisms. In this work, charge radii of nuclei with proton number $Z=40$ isotopes are systematically investigated based on the relativistic mean field model using the effective Lagrangian ${\mathrm{NL}3}^{*}$ and PK1 forces. The modified charge radii formula with consideration of the correction deduced from the neutron- and proton-pairs condensation around the Fermi surface is used to capture the local variations of nuclear size. The potential energy surfaces of even-even ${}^{80–110}\mathrm{Zr}$ isotopes are depicted by constraining the axially symmetric quadrupole and hexadecapole moments. The calculated results suggest that the characteristic nuclear shape coexistence phenomena can be clearly observed around the neutron number $N=60$ isotopes. The binding energy differences between the prolate and oblate minima and the systematic evolution of the quadrupole deformation parameters ${\beta }_{20}$ are analyzed as well. Combining the existing literature, the shape-phase transition around $N=60$ is identified from the rapid increase of charge radii, and the nuclei tend to keep prolate shape beyond $N=60$. This means that charge radii play an indispensable role in distinguishing the shape orientation of atomic nuclei. The modified charge radii formula can improve the description of the evolutionary trend of changes of charge radii. An inverted paraboliclike shape of charge radii between the neutron numbers $N=56$ and 68 is predicted. Meanwhile, a rapid increase in charge radii can be predicted across $N=68$.

The cluster degree of freedom has often been introduced to interpret the spectroscopic properties of exotic nuclei including $\alpha$-conjugate nuclei and a series of nuclei above double shell closures. In this study, we have systematically investigated the so-called unnatural-parity states and higher-lying bands for the typical nucleus ${}^{212}\mathrm{Po}$ based on the coupled-channels formalism, which allows the excitation of the core ${}^{208}\mathrm{Pb}$ plus multiple interactions. A general agreement between our calculations and the available data was obtained for the parity doublet bands and electromagnetic transition probabilities. Encouraged by that result, the present framework is extended to describe the nuclear properties of ${}^{216}\mathrm{Rn}$ with the configuration of heavier cluster plus core ${}^{208}\mathrm{Pb}$. Reasonable predictions of reduced transition rates and great improvement of energy bands for ${}^{216}\mathrm{Rn}$ were achieved beyond the treatment of the binary cluster-core model (BCM) without the coupling of cluster states, reconfirming the reliability of the present coupled-channels formalism. It is hoped that the current study can yield a new perspective on understanding the role of cluster degrees of freedom in heavy nuclei.

High spin states in ${}^{75}\mathrm{As}$ were investigated by using the ${}^{74}\mathrm{Ge}(\alpha ,p2n)$ reaction. A total of 27 transitions and 15 levels were newly identified in the level scheme. Based on the experimental characteristics of the observed rotational bands, the positive parity bands 2 and 3 are suggested as a signature partner band and a $\gamma$ vibrational band of the yrast band 1, respectively. The nearly degenerate negative parity doublet bands 4 and 5 were interpreted as a pair of pseudospin partner bands based on the relativistic density functional theory and the particle plus rotor model calculations. Additionally, evidence of octupole correlations were observed. The present work reports the coexistence of the soft triaxial and soft octupole deformations in atomic nuclei, which shows a diversity of nuclear shapes and collective excitations in this mass region.

The symmetry energy expansion is a useful way to parametrize the properties of dense matter near nuclear saturation density, and much work has been done to connect physical quantities like the neutron star radius and the core-crust transition density to the symmetry energy parameters. In this work, I connect the weak-interaction-driven bulk viscosity in neutron-proton-electron ($npe$) matter to the symmetry parameters by calculating the susceptibilities of dense matter in terms of the symmetry energy. I use this result to calculate the resonant-peak value of the bulk viscosity as a function of density, finding that it strongly depends on $L$, as does the minimum bulk-viscous dissipation timescale. Also resulting from this calculation is a formula for finding the conformal points of the zero-temperature equation of state. Finally, I determine for which values of the symmetry parameters the maximum $r$-mode-stable rotation frequency of an $npe$-matter neutron star is smaller than the Kepler frequency, in the high-temperature conditions where bulk viscosity is the dominant dissipation mechanism.

The influence of triaxial deformation $\gamma$ on the characteristics of chiral-parity (ChP) violation in nuclear systems is investigated within the reflection-asymmetric triaxial particle rotor model. With $\gamma$ deviating from ${90}^{\circ }$, the energy degeneracy between the chiral doublets and between the parity doublets of the ChP quartet bands is gradually reduced. The selection rules of the electromagnetic transitions are found to be sensitive to the triaxial deformation $\gamma$. The angular momentum geometry for the ChP quartet bands, including the angular momentum components and the azimuthal plot, is analyzed for different $\gamma$.