Missing mass spectroscopy with the ($e,e^{\prime }{K}^{+}$) reaction was performed at Jefferson Laboratory's Hall C for the neutron-rich $\mathrm{\Lambda }$ hypernucleus ${}_{\mathrm{\Lambda }}{}^9\mathrm{Li}$. The ground-state (g.s.) energy was obtained to be $B_{\mathrm{\Lambda }}^{\mathrm{g}.\mathrm{s}.}=8.84\pm 0.{17}^{\mathrm{stat}.}\pm 0.{15}^{\mathrm{sys}.}\mathrm{MeV}$ by using shell-model calculations of a cross-section ratio and an energy separation of the spin doublet states ($3/2_1^{+}$ and $5/2_1^{+}$). In addition, peaks that are considered to be states of $[{}^8\mathrm{Li}\left(3^{+}\right)\otimes s_{\mathrm{\Lambda }}=3/2_2^{+},1/2^{+}]$ and $[{}^8\mathrm{Li}\left(1^{+}\right)\otimes s_{\mathrm{\Lambda }}=5/2_2^{+},7/2^{+}]$ were observed at $E_{\mathrm{\Lambda }}\left(\mathrm{no}.2\right)=1.74\pm 0.{27}^{\mathrm{stat}.}\pm 0.{11}^{\mathrm{sys}.}$ and $E_{\mathrm{\Lambda }}\left(\mathrm{no}.3\right)=3.30\pm 0.{24}^{\mathrm{stat}.}\pm 0.{11}^{\mathrm{sys}.}\mathrm{MeV}$, respectively. The $E_{\mathrm{\Lambda }}\left(\mathrm{no}.3\right)$ is larger than shell-model predictions by a few hundred keV, and the difference would indicate that a ${}^5\mathrm{He}+t$ structure is more developed for the $3^{+}$ state than those for the $2^{+}$ and $1^{+}$ states in a core nucleus ${}^8\mathrm{Li}$ as a cluster model calculation suggests.

A model is developed, based on the density functional perturbation theory and the inverse Kohn-Sham method, that can be used to improve relativistic nuclear energy density functionals towards an exact but unknown Kohn-Sham Hartree-exchange-correlation functional. The improved functional is determined by empirical exact ground-state densities of finite systems. A test of the model and an illustrative calculation are performed, starting from two different approximate functionals, to reproduce the parameters and density dependence of a target functional, using exact ground-state densities of symmetric $N=Z$ systems.

We examine nucleon-nucleon realistic interactions, based on their SU(3) decomposition to SU(3)-symmetric components. We find that many of these interaction components are negligible, which, in turn, allows us to identify a subset of physically relevant components that are sufficient to describe the structure of low-lying states in ${}^{12}\mathrm{C}$ and related observables, such as excitation energies, electric quadrupole transitions, and rms radii. We find that paring down the interaction by half or more yields results that practically coincide with the corresponding ab initio calculations with the full interaction. In addition, we show that while various realistic interactions differ in their SU(3) decomposition, their renormalized effective counterparts exhibit a striking similarity and composition that can be linked to dominant nuclear features such as deformation, pairing, clustering, and spin-orbit effect.

Lifetimes of the low-energy levels in ${}^{136}\mathrm{Nd}$, populated in the reaction ${}^{124}\mathrm{Te}({}^{16}\mathrm{O},4n)$, were measured with the ROSPHERE array at the Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), Bucharest-Magurele. The data were analyzed using the recoil distance Doppler shift method, and, in the cases where lifetimes were $\tau ⩽1$ ps, Doppler attenuation effects were taken into account. The deduced electromagnetic transition probabilities are discussed in the framework of the five-dimensional collective Hamiltonian (5DCH) theoretical model implemented with the D1S Gogny force, and detailed systematics of several observables in the even-even Nd isotopic chain are presented that highlight the transitional character of the neutron-deficient Nd isotopes. The 5DCH predictions are in overall good agreement with the present experimental results.

The neutron-deficient gold $(Z=79)$ isotopes in the vicinity of the neutron midshell $N=104$ provide prolific examples of shape coexistence and isomerism at low excitation energy. They can be probed via a number of different experimental techniques. In this study, two new isomeric states with half-lives of 294(7) and 373(9) ns have been observed in the neutron-deficient odd-odd nuclide ${}^{178}\mathrm{Au}$ $(N=99)$ in an experiment at the RITU gas-filled separator at JYFL, Jyväskylä. This result was achieved due to the use of a segmented planar germanium detector with a high efficiency at low energies. By applying the recoil-decay tagging technique, they were assigned to decay to two different long-lived $\alpha$-decaying states in ${}^{178}\mathrm{Au}$.

We calculate proton elastic and inelastic scatterings with a microscopic coupled channel (MCC) calculation. The localized diagonal and coupling potentials including the spin-orbit part are obtained by folding a complex $G$-matrix effective nucleon-nucleon interaction with a transition density. This is the first time that the present folding prescription for the spin-orbit part is applied to the proton inelastic scattering, while for the monopole transition only. We apply the MCC calculation to the proton elastic and inelastic $\left(0_2^{+}\right)$ scatterings by ${}^{12}\mathrm{C}$ target at $E_p=65 \mathrm{and} 200 \mathrm{MeV}$. The role of diagonal and coupling potentials for the central and spin-orbit parts is checked. In addition, the relation between the transition density and the proton inelastic scattering is investigated with the modified wave function and the modified transition density. Namely, we perform the investigation with the artificial drastic change rather than fine structural change. The inelastic cross section is sensitive to the strength and shape of the transition density, but the inelastic analyzing power is sensitive only to the shape of that. Finally, we make clear the property of the inelastic analyzing power derived from the transition density without an ambiguity.

The interplay between quadrupole and octupole degrees of freedom is discussed in a series of neutron-rich actinides and superheavy nuclei with $92\le Z\le 110$ and $186\le N\le 202$. In addition to the static Hartree-Fock-Bogoliubov approach, dynamical beyond-mean-field correlations are taken into account via both parity restoration and symmetry-conserving generator coordinate method calculations based on the Gogny-D1M energy density functional. Physical properties such as correlation energies, negative-parity excitation energies, as well as reduced transition probabilities $B\left(E1\right)$ and $B\left(E3\right)$ are discussed in detail. It is shown that, for the studied nuclei, the quadrupole-octupole coupling is weak and to a large extent the properties of negative-parity states can be reasonably well described in terms of the octupole degree of freedom alone.

A complete calculation of the nuclear matrix elements (NMEs) for Majoron emitting neutrinoless double beta decay within the framework of IBM-2 for spectral indices $n=1,3,7$ is presented. By combining the results of this calculation with previously calculated phase-space factors (PSFs) we give predictions for expected half-lives. By comparing with experimental limits on the half-lives we set limits on the coupling constants $\langle g_{ee}^M\rangle$ of all proposed Majoron-emitting models.

Cluster dynamics and single-particle correlation are simultaneously treated for the description of the ground state of ${}^{12}\mathrm{C}$. The recent development of the antisymmetrized quasicluster model (AQCM) makes it possible to generate $jj$-coupling shell-model wave functions from $\alpha$ cluster models. The cluster dynamics and the competition with the $jj$-coupling shell-model structure can be estimated rather easily. In the present study, we further include the effect of single-particle excitation; the mixing of the two-particle–two-hole excited states is considered. The single-particle excitation is not always taken into account in the standard cluster model analyses, and the two-particle–two-hole states are found to strongly contribute to the lowering of the ground state owing to the pairing-like correlations. By extending AQCM, all of the basis states are prepared on the same footing, and they are superposed based on the framework of the generator coordinate method (GCM).

The Langevin approach is extendedly applied to study the dynamical process of nuclear fission within the Fourier shape parametrization, where the potential energy is calculated with the macroscopic-microscopic model based on the Lublin-Strasbourg drop model and the Yukawa-folded potential. The fragment mass distribution and the total kinetic energy as a function of heavy fragment mass in 14 MeV $n+{}^{235}\mathrm{U}$ fission are calculated and compared with the evaluated data from ENDF/B-VIII.0 and the experimental data. It is found that the Wall model for the friction tensor is available to describe both of the mass distribution and the total kinetic energy (TKE) distribution in the nuclear fission within the present model. In addition, the mass distributions and the TKE distributions in 14 MeV $n+{}^{233,236,238}\mathrm{U}$ and ${}^{239}\mathrm{Pu}$ fission are well described. Furthermore, the behavior of the correlation of the distance between the centers of mass of two fragments with the heavy fragment mass at the scission point is found to be consistent with that of the TKE distribution where the shortest $R_{12}$ locates around $A_h=135$ which is due to the influence of the shell effects.

We study the pole properties of $\mathrm{\Lambda }\left(1405\right)$ in a model-independent manner by applying the uniformized Mittag-Leffler expansion proposed in our previous paper. The resonant energy, width and residues are determined by expanding the observable as a sum of resonant-pole pairs under an appropriate parametrization which expresses the observable to be single valued, and fitting it to experimental data of the invariant-mass distribution of ${\pi }^{+}{\mathrm{\Sigma }}^{-}, {\pi }^{-}{\mathrm{\Sigma }}^{+}, {\pi }^0{\mathrm{\Sigma }}^0$ final states in the reaction $\gamma p\to K^{+}\pi \mathrm{\Sigma }$ and the elastic and inelastic cross section $K^{-}p\to K^{-}p, {\overline{K}}^{0}n, {\pi }^{+}{\mathrm{\Sigma }}^{-}, {\pi }^{-}{\mathrm{\Sigma }}^{+}$. As we gradually increase the number of pairs from one to three, the first pair converges while the second and third pairs emerge further and further away from the first pair, implying that the uniformized Mittag-Leffler expansion with three pairs is almost convergent in the vicinity of the $\mathrm{\Lambda }\left(1405\right)$. The broad peak structure between the $\pi \mathrm{\Sigma }$ and $\overline{K}N$ thresholds regarded to be $\mathrm{\Lambda }\left(1405\right)$ is explained by a single pair with a resonant energy of $1420\pm 1$ MeV, and a half- width of $48\pm 2$ MeV, which is consistent with the single-pole picture of $\mathrm{\Lambda }\left(1405\right)$. We conclude that the uniformized Mittag-Leffler expansion turns out to be a very powerful and simple method to obtain resonance energy, width, and residues from the near-threshold spectrum.

We study deuteron production using no-coalescence hydrodynamic $+$ transport simulations of central AuAu collisions at $\sqrt{s_{NN}}=7–200$ GeV. Deuterons are sampled thermally at the transition from hydrodynamics to transport and interact in transport dominantly via $\pi pn\leftrightarrow \pi d$ reactions. The measured proton, lambda, and deuteron transverse momentum spectra and yields are reproduced well for all collision energies considered. We further provide a possible explanation for the measured minimum in the energy dependence of the coalescence parameter $B_2\left(\sqrt{s_{NN}}\right)$ as well as for the difference between $B_2\left(d\right)$ for deuterons and that for antideuterons, $B_2\left(\overline{d}\right)$.

Background: The properties of very neutron rich nuclear systems are largely determined by the density dependence of the nuclear symmetry energy. The Korea-IBS-Daegu-SKKU (KIDS) framework for the nuclear equation of state (EoS) and energy density functional (EDF) offers the possibility to explore the symmetry-energy parameters such as $J$ (value at saturation density), $L$ (slope at saturation), $K_{\mathrm{sym}}$ (curvature at saturation), and higher-order ones independently of each other and independently of assumptions about the in-medium effective mass, as previously shown in the cases of closed-shell nuclei and neutron-star properties.

Purpose: We examine the performance of EoSs with different symmetry energy parameters on properties of nuclei and observations of neutron stars and gravitational waves in an effort to constrain in particular $L$ and $K_{\mathrm{sym}}$ or the droplet-model counterpart $K_{\tau }$.

Method: Assuming a standard EoS for symmetric nuclear matter, we explore several points on the hyperplane of $(J,L,K_{\mathrm{sym}}$ or $K_{\tau })$ values. For each point, the corresponding KIDS functional parameters and a pairing parameter are obtained for applications in spherical even-even nuclei. This is the first application of KIDS energy density functionals with pairing correlations in a spherical Hartree-Fock-Bogoliubov computational code. The different EoSs are tested successively on the properties of closed-shell nuclei, along the Sn isotopic chain, and on astronomical observations, in a step-by-step procedure of elimination and correction.

Results: A small regime of best-performing parameters is determined and correlations between symmetry-energy parameters are critically discussed. The results strongly suggest that $K_{\mathrm{sym}}$ is negative and no lower than $-200\mathrm{MeV}$, that $K_{\tau }$ lies between roughly $-400$ and $-300\mathrm{MeV}$ and that $L$ lies between 40 and 65 MeV, with $L⪅55\mathrm{MeV}$ more likely. For the selected well-performing sets, corresponding predictions for the position of the neutron drip line and the neutron skin thickness of selected nuclei are reported. The results are only weakly affected by the choice of effective mass values. Parts of the drip line can be sensitive to the symmetry energy parameters.

Conclusion: Using KIDS EoSs for unpolarized homogeneous matter at zero temperature and KIDS EDFs with pairing correlations in spherical symmetry we have explored the hyperplane of symmetry-energy parameters. Using both nuclear-structure data and astronomical observations as a testing ground, a narrow regime of well-performing parameters has been determined, free of nonphysical correlations and decoupled from constraints on the nucleon effective mass. The results underscore the role of $K_{\tau }$ and of precise astronomical observations. More-precise constraints are possible with precise fits to nuclear energies and, in the future, more-precise input from astronomical observations.

Background: Entanglement plays a central role in a diverse array of increasingly important research areas, including quantum computation, simulation, measurement, sensing, and communication. Extensive suites of investigations have been performed to better understand entanglement in atomic and molecular quantum many-body systems, while the exploration of entanglement in the structure of nuclei and their reactions is presently in its infancy.

Purpose: The goal of this work is to begin investigating the entanglement properties of nuclei from first-principles nuclear many-body calculations. We attempt to identify common features and emergent structures of entanglement that could ultimately lead to new and natural many-body schemes. With an eye toward quantum accelerators in future hybrid-supercomputers, criteria for partitioning nuclear many-body calculations into quantum and classical components may provide advantages in future large-scale computations. Along the way we look for explanations of the relative success of phenomenological models such as the nuclear shell model, and for better ways to match to low-energy nuclear effective field theories and lattice QCD calculations to nuclear many-body techniques that are based upon entanglement.

Method: We explore the entanglement between single-particle states in ${}^4\mathrm{He}$ and ${}^6\mathrm{He}$. The patterns of entanglement emerging from different single-particle bases are compared, and possible links with the convergence of observables are explored, in particular, ground-state energies. The nuclear wave functions are obtained by performing active-space no-core configuration-interaction calculations using a two-body nucleon-nucleon interaction derived from chiral effective field theory. Entanglement measures within single-particle bases exhibiting different degrees of complexity are determined, in particular, harmonic oscillator (HO), Hartree-Fock (HF), natural (NAT) and variational natural (VNAT) bases. Specifically, single-orbital entanglement entropy, two-orbital mutual information, and negativity are studied.

Results: The entanglement structures in ${}^4\mathrm{He}$ and ${}^6\mathrm{He}$ are found to be more localized within NAT and VNAT bases than within a HO basis for the optimal HO parameters we have worked with. In particular a core-valence structure clearly emerges from the full no-core calculation of ${}^6\mathrm{He}$. The two-nucleon mutual information shows that the VNAT basis, which typically exhibits good convergence properties, effectively decouples the active and inactive spaces.

Conclusions: Measures of one- and two-nucleon entanglement are found to be useful in analyzing the structure of nuclear wave functions, in particular the efficacy of basis states, and may provide useful metrics toward developing more efficient schemes for ab initio computations of the structure and reactions of nuclei, and quantum many-body systems more generally.

High-spin states of the odd-odd nucleus ${}^{168}\mathrm{Lu}$ were populated in the ${}^{123}\mathrm{Sb}({}^{48}\mathrm{Ca},3\mathrm{n}){}^{168}\mathrm{Lu}$ reaction at a beam energy of 203 MeV and decay $\gamma$ rays measured using the Gammasphere spectrometer array. The level scheme has been extended from spin 27 to 50 $\hslash$, and three new rotational bands have been added. A number of interband linking transitions were revealed, so that all but two bands could be connected with each other. High-spin band crossings, above the first $\nu i_{13/2}$ alignment, are delineated in most bands. Significant signature inversions are identified for the first time in the bands involving both favored and unfavored signatures of the $\pi h_{9/2}$ orbital, which are likely caused by a residual proton-neutron interaction. A signature inversion with small amplitude is also observed in the $\pi d_{5/2}\otimes \nu i_{13/2}$ band. Configurations are suggested for all bands based on their experimental properties, with the help of Cranked Shell Model calculations. No evidence is found for triaxial strongly deformed structures that were predicted by the calculations.

Excited states in ${}^{35}\mathrm{S}$ were investigated by in-beam $\gamma$-ray spectroscopy using the ${}^{26}\mathrm{Mg}({}^{18}\mathrm{O},2\alpha 1n)$ fusion-evaporation reaction. The deexciting $\gamma$ rays were measured with germanium detector arrays along with the measurement of evaporated charged particles in a $4\pi$-segmented Si detector array. The level scheme was extended up to 12.47 MeV. The obtained level structure is compared with the large-scale shell-model calculations. The possibility of isoscalar-pair excited states is discussed for $J=(17/2)$ states with comparison between the experimental and theoretical results.

It is shown that the excessive squeezing characteristic of the leptodermous droplet model can be eliminated by taking into account the finite thickness of the nuclear surface. The same objective was achieved in the finite-range droplet model by the introduction of an exponential correction term, but this model breaks down at the large deformations encountered in fission barriers. With this term now being seen to be superfluous, a unified droplet-model treatment of masses and fission barriers becomes possible.

We performed a high resolution study of $0^{+}$ states in ${}^{134}\mathrm{Ba}$ using the ${}^{136}\mathrm{Ba}(p,t)$ two-neutron transfer reaction. Our experiment shows a significant portion of the $L=0$ pair-transfer strength concentrated at excited $0^{+}$ levels in ${}^{134}\mathrm{Ba}$. Potential implications in the context of ${}^{136}\mathrm{Xe}\to {}^{136}\mathrm{Ba}$ neutrinoless double beta decay matrix element calculations are briefly discussed.

Recent experiments [Phys. Rev. Lett. 123, 092503 (2019); Phys. Rev. Lett. 118, 222501 (2017)] have made remarkable progress in measurements of the isotopic fission-fragment yields of the compound nucleus ${}^{239}\mathrm{U}$, which is of great interests for fast-neutron reactors and for benchmarks of fission models. We apply the Bayesian neural network (BNN) approach to learn existing evaluated charge yields and infer the incomplete charge yields of ${}^{239}\mathrm{U}$. We found that the two-layer BNN is improved compared to the single-layer BNN for overall performance. Our results support the normal charge yields of ${}^{239}\mathrm{U}$ around Sn and Mo isotopes. The role of odd-even effects in charge yields has also been studied.

Background: The ($p,p\alpha$) knockout reaction is useful for the study of preformed $\alpha$ clusters in atomic nuclei. At quasifree kinematic conditions above an incident energy of about 100 MeV the cross section and analyzing-power angular distributions extracted from the ($p,p\alpha$) knockout reaction are anticipated to resemble its free two-body counterparts. Several ($p,p\alpha$) knockout studies in the incident-energy range of 100–150 MeV on targets up to ${}^{12}\mathrm{C}$ confirm the predicted equivalence. However, the only experiment on ${}^{40}\mathrm{Ca}(p,p\alpha ){}^{36}\mathrm{Ar}$ appears to fail the expectation spectacularly.

Purpose: The reason for the drastic discrepancy between the experimental analyzing-power angular distribution for ${}^{40}\mathrm{Ca}(p,p\alpha ){}^{36}\mathrm{Ar}$ and the trend of free elastic scattering of protons from ${}^4\mathrm{He}$ is investigated.

Method: Guidance in general from the distorted-wave impulse approximation (DWIA) theory is employed. Specific focused theoretical calculations are performed.

Results: As expected, for the ($p,p\alpha$) reaction on several light target masses up to ${}^{12}\mathrm{C}$, comparable cross section and analyzing-power angular distributions resemble free ${}^4\mathrm{He}(p,p){}^4\mathrm{He}$ elastic scattering to a remarkable extent. The DWIA treatment for the ${}^{40}\mathrm{Ca}(p,p\alpha ){}^{36}\mathrm{Ar}$ reaction, however, needs a more careful selection of the distortion optical-model parameters in the $\alpha \text{−}\mathrm{Ar}$ outgoing channel. Global optical-model potentials used in the published work reproduce neither analyzing-power distribution of the ${}^{40}\mathrm{Ca}(p,p\alpha ){}^{36}\mathrm{Ar}$ reaction, nor $\alpha \text{−}{}^{36}\mathrm{Ar}$ elastic scattering cross-section angular distributions. Use of appropriate optical potentials resolves the problem.

Conclusions: The use of appropriate optical-model potentials which describe elastic scattering of $\alpha$ particles from ${}^{36}\mathrm{Ar}$ correctly appears to be crucial. The problem reported previously in the literature is resolved to a remarkable extent. There is a need to explore the two-body aspects of the quasifree ($p,p\alpha$) reaction for heavier targets further.