Nucleon-nucleon scattering is a fundamental process in low-energy nuclear physics. Although its spin correlations have been studied intensively, few works take the perspective of quantum information science. In this work, I explore the quantum information aspects of spin correlations in the partially polarized neutron-proton scattering in the $S$ wave. It is found that the spin mutual information, entanglement and discord of the out-states, when averaged over the possible in-states, all vary in a similar way with respect to the relative momentum. The novel connection between emergent symmetry and spin entanglement found by a previous study [Phys. Rev. Lett. 122, 102001 (2019)] could then be extended naturally to spin correlations beyond entanglement.

An outstanding problem in heavy-ion collisions is the inability for models to accurately describe ultracentral experimental flow data, despite that being precisely the regime where a hydrodynamic description should be most applicable. We reassess the status of this puzzle by computing the flow in ultracentral collisions obtained from multiple recent Bayesian models that were tuned to various observables in different collision systems at typical centralities. While central data can now be described with better accuracy than in previous calculations, tension with experimental observation remains and worsens as one goes to ultracentral collisions. Tuning the model parameters cannot remove this tension without destroying the fit at other centralities. As such, new elements are likely needed in the standard modeling of heavy-ion collisions.

The collision energy dependence of the cross section and the transverse momentum distribution of dielectrons from the Breit-Wheeler process in heavy-ion collisions are computed in the lowest-order QED and found to be sensitive to the nuclear charge distribution and the infrared divergence of the ultra-Lorentz-boosted Coulomb field. Within a given experimental kinematic acceptance, the cross section is found to increase while the pair transverse momentum ($\sqrt{\langle p_T^2\rangle }$) decreases with increasing beam energy. We demonstrate that the transverse-momentum component of Weizsäcker-Williams photons is due to the finite extent of the charge source and electric field component in the longitudinal direction. We further clarify the connection between the nuclear charge distribution and the kinematics of produced $e^{+}{e}^{-}$ from the Breit-Wheeler process, and propose a criterion for the validity of the Breit-Wheeler process in relativistic heavy-ion collisions. Following this approach we demonstrate that the experimental measurements of the Breit-Wheeler process in ultrarelativistic heavy-ion collisions can be used to quantitatively constrain the nuclear charge radius. The extracted parameters show sensitivity to the impact parameter dependence, and can be used to study the initial-state and final-state effects in hadronic interactions.

We extend the original idea of reduced nuclear amplitudes to capture individual helicity amplitudes and discuss various applications to exclusive processes involving the deuteron. Specifically, we consider deuteron form factors, structure functions, tensor polarization observables, photodisintegration, and electrodisintegration. The basic premise is that nuclear processes at high momentum transfer can be approximated by tree graphs for point-like nucleons supplemented by empirical form factors for each nucleon. The latter represent the internal structure of the nucleon, and incorporate nonperturbative physics, which can allow for early onset of scaling behavior. The nucleon form factors are evaluated at the net momentum transfer experienced by the given nucleon, with use of $G_E$ for a no-flip contribution and $G_M$ for a helicity-flip contribution. Results are compared with data where available. The deuteron photodisintegration asymmetry $\mathrm{\Sigma }$ is obtained with a value of $\mathrm{\Sigma }\left({90}^{\circ }\right)\simeq -0.06$, which is much closer to experiment than the value of $-1$ originally expected. The method also provides an estimate of the momentum transfer values required for scaling onset. We find that the deuteron structure function $B$ is a good place to look, above momentum transfers of 10 ${\mathrm{GeV}}^2$.

Traditionally neutrinoless double-electronic capture is considered as a resonance process. Degeneracy of the initial and daughter nuclei is the main factor mastering the decay rate. We have fulfilled shake-off probability calculations. Allowance for the shake-off loosens the need for resonance, leading to a radical increase of the capture rate in the nonresonance nuclei. In the case of ${}^{164}\mathrm{Er}$, the contribution of the new mechanism increases the capture rate by a factor of 5.6. It also increases the probability of electron capture from higher shells. The influence of the shake-off is also expected to manifest itself in the other $\beta$ processes which are used in the studies of the neutrino nature, its mass and role in the dark matter puzzle.

In this work, we compute the structure and composition of the inner crust of a neutron star in the presence of a strong magnetic field, such as can be found in magnetars. To determine the geometry and characteristics of the crust inhomogeneities, we consider the compressible liquid drop model, where surface and Coulomb terms are included in the variational equations, and we compare our results with previous calculations based on more approximate treatments. For the equation of state (EoS), we consider two nonlinear relativistic mean-field models with different slopes of the symmetry energy, and we show that the extension of the inhomogeneous region inside the star core due to the magnetic field strongly depends on the behavior of the symmetry energy in the crustal EoS. Finally, we argue that the extended spinodal instability observed in previous calculations can be related to the presence of small amplitude density fluctuations in the magnetar outer core, rather than to a thicker solid crust. The compressible liquid drop model formalism, while in overall agreement with the previous calculations, leads to a systematic suppression of the metastable solutions, thus allowing a more precise estimation of the crust-core transition density and pressure, and therefore a better estimation of the crustal radius.

The deformation properties of the low-lying states in ${}^{76}\mathrm{Ge}$ have been investigated following a safe-energy Coulomb excitation measurement with the GRETINA tracking array and CHICO2 heavy-ion counter at the ATLAS accelerator facility at Argonne National Laboratory. A comprehensive set of transition and static $E2$ matrix elements were extracted from the measured differential Coulomb cross sections and compared with results of configuration-interaction shell-model calculations and computations carried out within the framework of the generalized triaxial rotor model. The remarkable agreement between the calculated and experimental data supports a near-maximum triaxial deformation for the ground state of ${}^{76}\mathrm{Ge}$. In addition, the degree of softness of the asymmetry in ${}^{76}\mathrm{Ge}$ and ${}^{76}\mathrm{Se}$ was investigated using rotational invariants generated from configuration-interaction shell-model wave functions computed with the jj44b and JUN45 effective interactions. The resulting invariants are shown to be consistent with a stiff triaxial deformation in ${}^{76}\mathrm{Ge}$ and a predominantly soft triaxial potential for ${}^{76}\mathrm{Se}$, in agreement with the conclusions of recent works by this collaboration.

Background: The shape isomers of the $N=Z=\mathrm{even}$ nuclei are known from the energy-surface calculations within the Bloch-Brink (BB) $\alpha$-cluster model and Nilsson model. As an alternative, a new method (called SCS) has been proposed recently for determining the stable shapes, which is based on the investigation of the stability and consistency of the $\mathrm{SU}\left(3\right)$ symmetry (or quadrupole deformation).

Purpose: We wish to derive the shape isomers of the $\alpha$-like nuclei from the SCS method and compare them with the results of the energy-surface calculation. Furthermore, we intend to study the consequences of the stable symmetries. In particular, we investigate (i) what kind of binary clusterizations are structurally allowed for the shape isomers and (ii) if energy spectra similar to those of the BB model can be obtained with a simple dynamically symmetric Hamiltonian.

Methods: We determine the stability and self-consistency of the quadrupole deformation from a systematic calculation with the Nilsson model by applying the concept of the quasidynamical $\mathrm{U}\left(3\right)$ symmetry. The allowed cluster configurations are determined from the application of the U(3) and ${\mathrm{U}}^{\mathrm{ST}}\left(4\right)$ selection rules. The forbidden ones are characterized quantitatively. The energy spectrum is calculated with a simple dynamically symmetric Hamiltonian of the multiconfigurational dynamical symmetry (MUSY), which proved to be useful for the description of some experimental spectra.

Results: The shape isomers found from the SCS method are in good agreement with the results of the energy surface method (BB and Nilsson models). Their allowed binary clusterizations are obtained from structural selection rules, but they give a hint for the available reaction channels, too. Last, a very simple energy functional is able to reproduce the gross features of their energy spectra in a large range of excitation energy and deformation.

Conclusions: The similarity of the shape isomers from two very different methods gives a strong support to these predictions. The reasonable reproduction of the energy distribution of the “ground-band heads” is especially remarkable, considering the fact that MUSY is able to produce the complete spectra in detail, not only the energy minima.

Background: Due to the complex multidimensional dependence, the prediction and evaluation of independent fission yield distributions have always been a challenge.

Purpose: Considering the complex multidimensional dependence and high missing rate of independent yield data, this study applies the tensor decomposition algorithm to the prediction of independent fission yields.

Methods: Tensor decomposition algorithm is a type of machine-learning algorithm with strong multidimensional structural dependencies capture ability, which is often used in the imputation of missing data in sparse tensors and has achieved great success in fields such as image processing and data mining. After constructing yield tensors with three dimensions for 851 fission products and filling the tensors with the independent yield data from the ENDF/B-VIII.0 database, the tensor decomposition algorithm is applied to predict the independent isotope yield in fission, which results the fission yield tensor decomposition (FYTD) model.

Results: The fission yields of ${}^{235}\mathrm{U}$ and ${}^{239}\mathrm{Pu}$ are set as missing values and then predicted. The mass distribution of ${}^{235}\mathrm{U}$ fissions yield predicted by the FYTD model agrees well with the prediction of BNN $+$ TALYS model and ENDF/B-VIII.0 data. Furthermore, the isotope yields in the fissions are also predicted. For fast neutron-induced fission of ${}^{239}\mathrm{Pu}$, 98% predictions of the isotope yields by the FYTD model agree with the ENDF/B-VIII.0 data within one order of magnitude. The fission yields of ${}^{238}\mathrm{Np}$, ${}^{243}\mathrm{Am}$, and ${}^{236}\mathrm{Np}$ that do not exist in the ENDF/B-VIII.0 database are predicted and compared with those in the JEFF-3.3 database, as well as the experimental data. Good agreement demonstrates the predictive ability of the FYTD model for the target nucleus dependence. The scalability of the FYTD model over the incident neutron energy degrees of freedom is examined. After adding a set of 2 MeV neutron-induced ${}^{239}\mathrm{Pu}$ fission yield data into the yield tensor, the 2 MeV neutron-induced fission yields of ${}^{235}\mathrm{U}$ and ${}^{229}\mathrm{Th}$ are predicted and consistent with the prediction of the GEF model and experimental data. Finally, the yields of the ratio of isomeric states and neutron excess of the products as a function of product charge number are also predicted and verified.

Conclusions: The FYTD model can capture the multidimensional dependence of the fission yield data and make reasonable predictions. This study proves the effectiveness of tensor decomposition algorithm in fission product yield study, and provides new ideas and tools for the evaluation and prediction of fission product yield data.

Both nonresonant and resonance reaction data are subject to laboratory electron screening effects. For nonresonant reactions, such effects are well documented and the measured cross sections can be corrected to find the unscreened ones. Frequently, the procedure and expression to calculate laboratory electron screening factors for nonresonant reactions are also applied to isolated narrow resonances, without much theoretical support or experimental evidence. A simple model is applied to estimate electron screening factors, lengths, and potentials for narrow resonances. The corrections to the measured data result in an enhancement of the unscreened resonance strengths by less than 0.2%, contrary to published narrow-resonance screening correction factors, which predict a reduction of the unscreened strengths by up to 25%. Unless it can be proven otherwise, it is recommended that measured strengths of isolated narrow resonances not be corrected for laboratory electron screening. The prospects of investigating laboratory electron screening effects by measuring almost negligible differences in resonance strengths are not promising. Instead, the difference of the resonance energy for the unscreened and screened situation may be measurable. As an example, the case of the $E_r=956$-keV resonance in the ${}^{27}\mathrm{Al}(p,\gamma ){}^{28}\mathrm{Si}$ reaction is discussed. It is also demonstrated that the claim of a previously reported detection of a resonance near 800 keV in the ${}^{176}\mathrm{Lu}(p,n){}^{176}\mathrm{Hf}$ reaction is incorrect.

We extend the many-body expansion (MBE), previously applied to hydrogen bonded and molecular systems, to the light nuclear systems ${}^3\mathrm{H}$ and ${}^3\mathrm{He}$ by considering the nucleonic degrees of freedom as fundamental in the expansion. The analysis is based on the Pauli nucleonic dynamics (PND) model, a simple antisymmetrized dynamical code, inspired by the sophisticated constrained molecular dynamics (CoMD) model. The total energy of the ${}^2\mathrm{H}$ nucleus is calculated with this model at −2.312 MeV, which is within 4% of the experimental value of −2.225 MeV. The application of the MBE yields results for the three-body term in the ${}^3\mathrm{H}$ nucleus that is comparable with previous estimates, while it is reported for the first time for the nucleus of ${}^3\mathrm{He}$. The energies of ${}^3\mathrm{H}$ and ${}^3\mathrm{He}$ that include the sum of the one- and two-body terms with the model are $-6.97\pm 0.21$ MeV and $-6.19\pm 0.21$ MeV and the three-body terms, estimated from the difference of the sum of the one- and two-body terms from the experimentally measured energies, are $-1.51\pm 0.21$ MeV and $-1.53\pm 0.21$ MeV, respectively. The MBE for the ${}^3\mathrm{H}$ and ${}^3\mathrm{He}$ nuclei is qualitatively similar to the one previously reported for the water trimer: the two- and three-body terms are negative with the latter amounting to $\sim 3\%$ of the former. Additionally, the three-body terms correspond to about 16–23% of the total energy of the bound systems, a percentage that is also comparable to the one in the water trimer (17%). In this manner, the MBE analysis can be applied to light nuclear systems following the same protocol as the one that has been previously extensively used for hydrogen bonded molecular systems.

Background: The statistical approach is usually applied for the description of electromagnetic decay of the nucleus with the exception of the lowest excitation energies as well as for the calculation of the interaction of photons with nuclei, in particular the reaction cross sections. This concept employs nuclear level density (NLD) and photon strength functions (PSFs).

Purpose: While PSFs and NLD of some well-deformed rare-earth nuclei were measured by several methods, sometimes with conflicting results, the PSFs of ${}^{168}\mathrm{Er}$ were addressed only by $(\gamma ,{\gamma }^{\prime })$ experiments. On the other hand, the low-lying levels of ${}^{168}\mathrm{Er}$ are well studied, including the isomeric state at 1094 keV, which enables various tests of the statistical approach.

Methods: The $\gamma$ rays following radiative neutron capture on a ${}^{167}\mathrm{Er}$ sample were measured with the highly segmented $\gamma$-ray calorimeter Detector for Advanced Neutron Capture Experiments at the Los Alamos Neutron Science Center. The $\gamma$-ray energy spectra for different multiplicities (multistep cascade, or MSC, spectra) were gathered for many $s$-wave resonances of both possible spins. Moreover, we were able to detect the decay of the short-lived isomer and deduce the isomeric ratio for a few resonances.

Results: Analysis of the MSC spectra within the statistical model enabled us to draw conclusions about dipole PSFs, in particular on the properties of the scissors mode, and NLD. The spectra can be well reproduced with phenomenological PSFs models but not with any of several models based on quasiparticle random-phase approximation (QRPA) calculations with different interactions. We showed that nonstatistical effects in feeding of the isomeric state play a role up to excitation energies of at least about 2 MeV.

Conclusions: Deduced parameters of the scissors mode were found to be similar to those of neighbor well-deformed even-even Gd and Dy nuclei. Models like that of Kadmenskij, Markushev, and Furman (KMF) or like the modified generalized Lorentzian (MGLO) model provide a good description of experimental spectra. In contrast to several previous analyses of well-deformed rare-earth isotopes, we were able to match the experimental isomeric ratio with statistical model simulations.

We consider the hydrodynamic evolution of a quark-gluon gas with nonzero quark masses and net baryon number in its phase diagram. For far-off-equilibrium initial conditions the expansion trajectories appear to violate simple rules based on the second law of thermodynamics that were previously established for ideal or weakly dissipative fluids. For Bjorken flow we present a detailed analysis within kinetic theory that provides a full microscopic understanding of these macroscopic phenomena and establishes their thermodynamic consistency. We point out that, for certain far-off-equilibrium initial conditions, the well-known phenomenon of “viscous heating” turns into “viscous cooling” where, driven by dissipative effects, the temperature decreases faster than in adiabatic expansion.

We try to resolve the longstanding controversy over the low-lying $1/2^{+}$ state in ${}^9\mathrm{B}$. Experimentally, the energies for this state show a gap between various measurements done by different groups and some of them reported that the existence of the state is unclear. The situation is similar in the theoretical calculations. We study the existence and structure of the ${}^9\mathrm{B}(1/2^{+}$) state based on our previous method for the $\alpha +\alpha +N$ cluster model with the complex scaling method that well explains the measured photodisintegration cross section for the ${}^9\mathrm{Be}(1/2^{+})$. We find two resonances at the energies of $E_1^{\mathrm{res}}=1.81$ MeV with a decay width $\mathrm{\Gamma }=1.98$ MeV and $E_2^{\mathrm{res}}=2.38$ MeV, $\mathrm{\Gamma }=1.81$ MeV in ${}^9\mathrm{B}$. The charge radii and the three-body channel configurations are calculated to see the properties of two resonances. We also calculate the level density of two resonances, which indicates the difficulty to distinguish them in the energy distribution.

Nuclear matter is studied within the density functional theory framework. Our method employs a finite number of nucleons in a box subject to periodic boundary conditions, in order to simulate infinite matter and study its response to an external static potential. We detail both the theoretical formalism and its computational implementation for pure neutron matter and symmetric nuclear matter with Skyrme-like energy density functionals (EDFs). The implementation of spin-orbit, in particular, is carefully discussed. Our method is applied to the problem of the static response of nuclear matter and the impact of the perturbation on the energies, densities, and level structure of the system is investigated. Our work is a crucial step in our program of ab initio based nuclear EDFs [Phys. Rev. C 104, 024315 (2021)] as it paves the way towards the goal of constraining the EDF surface terms on ab initio calculations.

Prompt and $\beta$-delayed fission observables, such as the average number of prompt and delayed neutrons, the independent and cumulative fission product yields, and the prompt $\gamma$-ray energy spectra for the photonuclear reactions on ${}^{235,238}\mathrm{U}$ and ${}^{239}\mathrm{Pu}$, are calculated with the Hauser-Feshbach fission fragment decay (${\mathrm{HF}}^3\text{D}$) model and compared with available experimental data. In the analysis of neutron-induced fission reactions to the case of photo-induced fission, an excellent reproduction of the delayed neutron yields supports a traditional assumption that the photo fission might be similar to the neutron-induced fission at the same excitation energies regardless of the spin and parity of the fissioning systems.

Calculation of the nuclear matrix elements (NMEs) for double-$\beta$ decay is of paramount importance for guiding experiments and for analyzing and interpreting the experimental data, especially for the search of the neutrinoless double $\beta$ decay mode ($0\nu \beta \beta$). However, there are currently still large differences between the NME values calculated by different methods, hence a quantification of their uncertainties is very much required. In this paper we propose a statistical analysis of $0\nu \beta \beta$ NME for the ${}^{136}\mathrm{Xe}$ isotope, based on the interacting shell model, but using three independent effective Hamiltonians, emphasizing the range of the NMEs' most probable values and its correlations with observables that can be obtained from the existing nuclear data. Consequently, we propose a common probability distribution function for the $0\nu \beta \beta$ NME, which has a range of (1.55–2.65) at 90% confidence level, with a mean value of 1.99 and a standard deviation of 0.37.

Halos and changes of nuclear magicities have been extensively investigated in exotic nuclei during past decades. The newly discovered ${}^{39}\mathrm{Na}$ with the neutron number $N=28$ provides a new platform to explore such novel phenomena near the neutron dripline of the sodium isotopic chain. We study the shell property and the possible halo structure in ${}^{39}\mathrm{Na}$ within the deformed relativistic Hartree-Bogoliubov theory in continuum. It is found that the lowering of $2p$ orbitals in the spherical limit results in the collapse of the $N=28$ shell closure in ${}^{39}\mathrm{Na}$, and a well-deformed ground state is established. The pairing correlations and the mixing of $pf$ components driven by deformation lead to the occupation of weakly bound or continuum $p$-wave neutron orbitals. An oblate halo is therefore formed around the prolate core in ${}^{39,41}\mathrm{Na}$, making ${}^{39}\mathrm{Na}$ a single nucleus with the coexistence of several exotic structures, including the quenched $N=28$ shell closure, Borromean structure, deformed halo, and shape decoupling. The microscopic mechanisms behind the shape decoupling phenomenon and the development of halos towards dripline are revealed.

In this work, we study the pairing Hamiltonian with four particles at finite temperatures on a quantum simulator and a superconducting quantum computer. The excited states are obtained by the variational quantum deflation. The error-mitigation methods are applied to improve the noisy results. The simulation of thermal excitation states is performed using the same variational circuit as at zero temperature. The results from quantum computing become close to exact solutions at high temperatures, and demonstrate a smooth superfluid-normal phase transition as a function of temperatures as expected in finite systems.