We investigate roles of the tensor force (TF) on the pairing correlations in the ground-state structure of ${}^{12}\mathrm{C}, {}^{16}\mathrm{O}, {}^{20}\mathrm{Ne}$, and ${}^{32}\mathrm{S}$ nuclei within a deformed BCS model. For pairing matrix elements, we exploit the Brueckner $G$ matrix derived from the charge-dependent Bonn potential. In particular, the isoscalar (IS) neutron-proton ($np$) pairing is studied in detail in relation to spin-triplet even TF in the nucleon-nucleon interaction. Detailed analyses of the $np$ pairing and possible enhancement of the IS channel are performed by focusing on roles of attractive spin-triplet even and repulsive spin-triplet odd channels in the TF for the ground states of the nuclei with some deformation. It is also shown that the TF may play a crucial role of properly interpreting the experimental data of a two-nucleon knockout reaction from ${}^{12}\mathrm{C}$.

The occurrence of octupole shapes in even-mass neutron-rich Ba isotopes has been well established. However, the situation with the odd-mass Ba and odd or odd-odd La nuclei around them is not so clear. In order to shed light on these less-studied isotopes, a fast-timing experiment was performed using the GRIFFIN spectrometer at TRIUMF-ISAC. A wealth of excited-state lifetimes in the 100 ps to few ns range have been measured in ${}^{144,145,146}\mathrm{Ba}$ and ${}^{145,146}\mathrm{La}$ populated in the ${\beta }^{-}$ and ${\beta }^{-}\text{−}n$ decay of ${}^{145,146}\mathrm{Cs}$. The results do not allow one to draw firm conclusions about the possible octupole deformation of these nuclei but suggest different spin and parity assignments than previous works. This work highlights the need for more detailed study of the odd and odd-odd isotopes in this region to properly understand their structure.

Both the incompressibility $K_A$ of a finite nucleus of mass $A$ and that ($K_{\infty }$) of infinite nuclear matter are fundamentally important for many critical issues in nuclear physics and astrophysics. While some consensus has been reached about $K_{\infty }$, accurate theoretical predictions and experimental extractions of $K_{\tau }$ characterizing the isospin dependence of $K_A$ have been very difficult. We propose a differential approach to extract $K_{\tau }$ and $K_{\infty }$ independently from the $K_A$ data of any two nuclei in a given isotope chain. Applying this method to the $K_A$ data from isoscalar giant monopole resonances (ISGMR) in even-even Pb, Sn, Cd, and Ca isotopes taken by Garg et al. at the Research Center for Nuclear Physics (RCNP), Osaka University, Japan, we find that the ${}^{106}\mathrm{Cd}\text{−}{}^{116}\mathrm{Cd}$ and ${}^{112}\mathrm{Sn}\text{−}{}^{124}\mathrm{Sn}$ pairs having the largest differences in isospin asymmetries in their respective isotope chains measured so far provide consistently the most accurate up-to-date $K_{\tau }$ value of $K_{\tau }=-616\pm 59$ MeV and $K_{\tau }=-623\pm 86$ MeV, respectively, largely independent of the remaining uncertainties of the surface and Coulomb terms in expanding $K_A$, while the $K_{\infty }$ values extracted from different isotopes chains are all well within the current uncertainty range of the community consensus for $K_{\infty }$. Moreover, the size and origin of the “soft Sn puzzle” is studied with respect to the “stiff Pb phenomenon.” It is found that the latter is favored due to a much larger (by $\approx 380$ MeV) $K_{\tau }$ for Pb isotopes than for Sn isotopes, while $K_{\infty }$ from analyzing the $K_A$ data of Sn isotopes is only about 5 MeV less than that from analyzing the Pb data.

We present a model independent method to reconstruct the impact parameter distributions of experimental data for intermediate energy heavy ion collisions, adapted from a recently proposed approach for ultra-relativistic heavy ion collisions. The method takes into account the fluctuations which are inherent to the relationship between any experimental observable and the impact parameter in this energy range. We apply the method to the very large dataset on heavy ion collisions in the energy range 20–100 MeV/nucleon obtained with the INDRA multidetector since 1993, for two observables which are the most commonly used for the estimation of impact parameters in this energy range. The mean impact parameters deduced with this new method for “central” collisions selected using typical observable cuts are shown to be significantly larger than those found when fluctuations are neglected, and as expected the difference increases as bombarding energy decreases. In addition, we will show that this new approach may provide previously inaccessible experimental constraints for transport models, such as an estimation of the extrapolated mean value of experimental observables for $b=0$ collisions. The ability to give more realistic, model independent estimations of the impact parameters associated with different experimental datasets should improve the pertinence of comparisons with transport model calculations which are essential to better constrain the equation of state of nuclear matter.

Many newly discovered excited states are interpreted as bound states of hadrons. Can these hadrons also form resonant states? In this paper, we extend the complex scaling method to calculate the bound state and resonant state consistently for the ${\mathrm{\Lambda }}_{c}D\left(\overline{D}\right)$ and ${\mathrm{\Lambda }}_c{\mathrm{\Lambda }}_c\left({\overline{\mathrm{\Lambda }}}_c\right)$ systems. For these systems, the $\pi ,\eta ,\rho$ meson exchange contributions are suppressed, the contributions of intermediate- and short-range forces from $\sigma /\omega$ exchange are dominant. Our results indicate that ${\mathrm{\Lambda }}_{c}D$ system can not form bound state and resonant state. There exist resonant states in a wide range of parameters for ${\mathrm{\Lambda }}_c\overline{D}$ and ${\mathrm{\Lambda }}_c{\mathrm{\Lambda }}_c\left({\overline{\mathrm{\Lambda }}}_c\right)$ systems. For these systems, the larger the bound state energy, the easier to form resonant states. Among all the resonant states, the energies and widths of the P wave resonant states are smaller and more stable, which is possible to be observed in the experiments. The energies of D and F wave resonant states can reach dozens of MeV and the widths can reach hundreds of MeV.

Shell structure effects on $\alpha$-cluster formation and decay are studied by using the quartetting wave function approach (QWFA). Both the intrinsic and center-of-mass (c.o.m.) motions of an $\alpha$ cluster inside a core nucleus are investigated with different contributing shell model wave functions. The overlap between intrinsic wave functions of four nucleons in the $\alpha$-like quartet state and in a free $\alpha$ particle is analyzed in detail. The change of the effective potential describing the c.o.m. motion of the quartet is explicitly shown for the major shell closures $Z=82$ and $N=126$. It is found that both the $\alpha$-cluster formation probability and the half-life are sensitive to the quartet shell model states. By extending the QWFA calculations from ${}^{212}\mathrm{Po}$ to $\alpha$ emitters with one or two extra nucleons, we show that the bound state and scattering wave functions of the $\alpha$ cluster are changed accordingly. The calculated $\alpha$-decay half-lives agree nicely with the experimental data.

Available experimental neutron skin thicknesses of even-even stable Ca, Ni, Sn, Pb, and Cd isotopes are evaluated, and separate trends of neutron skin thickness versus relative neutron excess $\delta =(N-Z)/A$ are observed for different isotopic chains. This phenomenon is quantitatively reproduced by the deformed Skyrme Hartree-Fock $+$ Bardeen-Cooper-Schrieffer model with SLy4 force.

The low-lying collective states in ${}^{192}\mathrm{Os}$ are investigated microscopically by means of the boson expansion theory with the self-consistent effective interactions. The building blocks of the collective boson, the collective potential, and the structures of the wave functions for some relevant states are illustrated. Calculated level energies and electromagnetic properties are compared with the experimental data. Properties of some low-lying states and relevant quasibands are discussed with the help of the boson description of state vectors.

Experimental data for pion photoproduction including differential cross sections and various polarization observables from four reaction channels, $\gamma p\to {\pi }^{0}p, \gamma p\to {\pi }^{+}n, \gamma n\to {\pi }^{-}p$, and $\gamma n\to {\pi }^{0}n$, from threshold up to $W=2.2$ GeV were used in order to perform a single-energy partial-wave analysis with minimal model dependence by imposing constraints from unitarity and fixed-$t$ analyticity in an iterative procedure. Reaction models were only used as a starting point in the very first iteration. We demonstrate that with this procedure partial-wave amplitudes can be obtained which show only a minimal dependence on the initial model assumptions. The analysis was obtained in full isospin, and the Watson theorem is enforced for energies below $W=1.3$ GeV but is even fulfilled up to $W\approx 1.6$ GeV in many partial waves. Electromagnetic multipoles $E_{\ell \pm }$ and $M_{\ell \pm }$ are presented and discussed for $S,P,D$, and $F$ waves.

The properties of the scattering solutions obtained as poles of the $S$ and $K$ matrices are analyzed in terms of pairing effects in the framework of the Hartree-Fock-Bogoliubov (HFB) Jost function. As a result of our analysis, we found the following: in order for the poles of the $S$ matrix to form a resonance, there must be a pole of the $K$ matrix nearby. Within the framework of HFB theory, there are three types of resonance states; shape resonances, particle-type, and hole-type quasiparticle resonances. Other scattering states that can be classified are independent $K$- and $S$-matrix poles. It is shown both numerically and qualitatively using the Jost function that the pair-correlation effect is hardly observed in the shape resonance state, and that the appearance of the pair-correlation effect is different in the particle-type and hole-type quasiparticle resonance. We also found a noteworthy correlation effect that independent $K$-matrix poles break the metastable structure of the wave function of the quasiparticle resonance and turn it into an independent $S$-matrix pole. The correlation effect that the poles of the independent $S$ matrix break the metastable structure of the inner wave function without breaking the resonance structure of the outer wave function when a pole of the independent $S$ matrix is near the hole-type resonance state was also revealed. This is considered to be another aspect of the Fano effect.

The universal fusion function prescription and the empirical coupled-channel (ECC) model are used to analyze the dynamic effects on fusion cross sections for reactions ${}^{32,34,36}\mathrm{S}+{}^{204,206,208}\mathrm{Pb}$. An examination of the reduced fusion functions shows that the total dynamic effects on fusion cross sections in ${}^{36}\mathrm{S}+{}^{204,206,208}\mathrm{Pb}$ are almost the same as those in ${}^{34}\mathrm{S}+{}^{204,206,208}\mathrm{Pb}$. Furthermore, at sub-barrier energies of the reactions ${}^{32,34,36}\mathrm{S}+{}^{208}\mathrm{Pb}$, the largest enhancement of reduced fusion function is observed in the reaction ${}^{32}\mathrm{S}+{}^{208}\mathrm{Pb}$. Then the enhancement of fusion cross sections due to couplings to inelastic excitation channels and neutron transfer channels with positive $Q$ values is investigated by using the ECC model. The results show that the experimental data of the reactions ${}^{34,36}\mathrm{S}+{}^{204,206,208}\mathrm{Pb}$ and ${}^{32}\mathrm{S}+{}^{208}\mathrm{Pb}$ are reproduced well by the ECC model. In addition, it can be found that the effect of coupling to positive $Q$-value neutron transfer channels is necessary to reproduce the sub-barrier fusion data of the reaction ${}^{32}\mathrm{S}+{}^{208}\mathrm{Pb}$. Furthermore, for the two reactions ${}^{32}\mathrm{S}+{}^{204}\mathrm{Pb}$ and ${}^{32}\mathrm{S}+{}^{206}\mathrm{Pb}$, the effects of coupling to positive $Q$-value neutron transfer channels are predicted to be significant. The fusion cross sections for these two reactions are also predicted.

Background: ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ collisions at a beam energy of 270 $\mathrm{MeV}/\mathrm{nucleon}$ were performed at the Radioactive Isotope Beam Factory (RIBF) in RIKEN to investigate the nuclear equation of state. Reconstructing the impact parameter is one of the important tasks in the experiment as it relates to many observables.

Purpose: In this work, we employ three commonly used algorithms in machine learning, the artificial neural network (ANN), the convolutional neural network (CNN), and the light gradient boosting machine (LightGBM), to determine the impact parameter by analyzing either the charged particle spectra or several features simulated with events from the ultrarelativistic quantum molecular dynamics (UrQMD) model.

Method: To closely imitate experimental data and investigate the generalizability of the trained machine learning algorithms, incompressibility of nuclear equation of state and the in-medium nucleon-nucleon cross sections are varied in the UrQMD model to generate the training data.

Results: The mean absolute error $\mathrm{\Delta }b$ between the true and the predicted impact parameter is smaller than 0.45 fm if training and testing sets are sampled from the UrQMD model with the same parameter set. However, if training and testing sets are sampled with different parameter sets, $\mathrm{\Delta }b$ would increase to 0.8 fm.

Conclusion: The generalizability of the trained machine learning algorithms suggests that these machine learning algorithms can be used reliably to reconstruct the impact parameter in experiments.

The abundance of light nuclei and hyperons, that are produced in stellar environments such as supernova or binary mergers, is calculated within a relativistic mean-field model with density-dependent couplings in low-density matter. Five light nuclei are considered, together with three light hypernuclei. We show that the presence of hyperons shifts the dissolution of clusters to larger densities, and increases the amount of clusters. This effect is larger the smaller the charge fraction, and the higher the temperature. The abundance of hyperons is also affected by the cluster formation: neutral and positively charged hyperons suffer a reduction, and the negatively charged ones an increase. We also observe that the dissolution of the less-abundant clusters occurs at larger densities due to smaller Pauli-blocking effects. Overall, hypernuclei set in at temperatures above 25 MeV, and, depending on the temperature and chemical composition, they may be more abundant than $\alpha$ particles, or even more abundant than other heavier clusters.

The low-lying positive-parity structures of ${}^{82}\mathrm{Kr}$ have been investigated following their population in the ${}^{76}\mathrm{Ge}({}^9\mathrm{Be},3n)$ reaction at ${\mathrm{E}}_{\mathrm{lab}}\approx 31\mathrm{MeV}$ and using a large array of Compton suppressed HPGe clovers as the detection setup. Apart from other spectroscopic measurements, level lifetimes of the states have been extracted using the Doppler shift attenuation method. The level energies and the associated transition probabilities exhibit superlative overlap with the calculations in the framework of the interaction boson approximation and the E(5) model. The ${}^{82}\mathrm{Kr}$ nucleus, thus, exemplifies the critical point of phase (shape) transition from the U(5) (spherical vibrator) to the O(6) ($\gamma$-soft rotor) paradigms of nuclear structure.

We present the quantum simulation of the deuteron to calculate its binding energy using the variational quantum eigensolver, which is based on a hybrid quantum-classical approach. Apart from a commonly used Hamiltonian derived from pionless effective field theory, we consider the interaction which can be easily studied with conventional classical methods but the corresponding operator leading to nonzero off-tridiagonal matrix elements. To map the many-body basis states on the qubit states, three encodings are explored, namely, one-hot, Bravyi-Kitaev, and the Gray code. We perform a generalized transformation for many-body operators in Gray code encoding, and simulate the Hamiltonians with nonzero off-tridiagonal matrix elements. Furthermore, the analyses of the relative efficiency of all encodings and corresponding transformations are carried out using the noise model of a real IBM quantum device. We demonstrate that the Gray code is more efficient for a large basis, irrespective of the form of potential and the presence of hardware noise.

Multinucleon transfer mechanisms near barrier collisions between very heavy nuclei are investigated in the framework of the improved dinuclear system model by considering the influence of orientation effects combined with statistical model code gemini++. Several transfer reactions for different actinide targets (${}^{238}\mathrm{U},{}^{248}\mathrm{Cm}$, and ${}^{249}\mathrm{Cf}$) are studied in detail. One notices that the isotopic distributions of the above-target products decrease drastically by a factor of 10 per proton, which is moved from projectile to target. However, the calculated and measured results show that the larger production cross sections above targetlike fragments can be produced by using the heaviest available target. The predicted cross sections and excitation functions of the new transfermium isotopes may be useful for future experiments.

In a recent paper [Phys. Rev. C 101, 014305 (2020)], Dong and Shang claim that the Skyrme original tensor interaction is invalid. Their conclusion is based on the misconception that the Fourier transform of tensor interaction is difficult or even impossible so that the Skrme-type tensor interaction was introduced in an unreasonable way. We disagree with their claim. In this Comment, we show that one can easily get the Skyrme force in momentum space by Fourier transformation if one starts from a general central, spin-orbit, or tensor interaction with a radial dependence.

The $\alpha$-core structure has been constructed to successfully interpret the band spectra of a series of nuclei above the double shell closure, plus the extension to the heavier cluster structure in the actinide region. By refining the binary cluster model, we show that such kind of picture can be applicable to more heavy nuclei, implying that there can exist cluster states in any heavy nuclei. As for superheavy nuclei, the involved cluster, analogous to the heavy particle radioactivity, is allowed to be above $Z>28$ plus the core ${}^{208}\mathrm{Pb}$. In this sense, besides some predictions on energy spectra of cluster states in superheavy nuclei, the very recently reported $2^{+}$ state of ${}^{282}\mathrm{Cn}$ is diagnosed to be not in the ground state rotational band via the present method. During the whole procedure, the uncertainty of the cluster model is determined for the first time, by the nonparametric resampling strategy, to make the whole theoretical results reliable and complete.

The short-range correlation induced by the tensor force in the isosinglet neutron-proton interaction channel leads to a high-momentum tail (HMT) in the single-nucleon momentum distributions $n\left(k\right)$ in nuclei. Owing to the remaining uncertainties about the tensor force, the shape of the nucleon HMT may be significantly different from the dilute interacting Fermi gas model prediction $n\left(k\right)\sim 1/k^4$ similar to the HMT in cold atoms near the unitary limit. Within an isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck transport model incorporating approximately the nucleon HMT, we investigate hard photon emissions in ${}^{14}\mathrm{N}+{}^{12}\mathrm{C}$ and ${}^{48}\mathrm{Ca}+{}^{124}\mathrm{Sn}$ reactions at beam energies around the Fermi energy. Imprints of different shapes of the HMT on the energy spectrum, angular distribution, and transverse momentum spectrum of hard photons are studied. While the angular distribution does not carry any information about the shape of the nucleon HMT, the energy spectra and especially the midrapidity transverse momentum spectra of hard photons are found to bare strong imprints of the shapes of nucleon HMTs in the two colliding nuclei.