We examine the properties of composite octet baryons in the nuclear medium and neutron-star matter. The internal quark-diquark structure of the octet baryons and the equations of state of nuclear matter and neutron-star matter in the mean field approximation are described by using the three-flavor Nambu–Jona-Lasinio (NJL) model as an effective quark theory of quantum chromodynamics. After introducing our model, we first discuss the properties of single baryons and their effective meson exchange interactions in symmetric nuclear matter by using concepts of Fermi-liquid theory. Several model-independent implications of this description are derived and illustrated by numerical results obtained in our model. Second, we extend the model description to high baryon densities and investigate the equation of state of neutron-star matter and the resulting star masses. We find that the so-called hyperon puzzle persists also for the case of composite hadrons. To get more information on this point, we also investigate the role of 6-Fermi and 8-Fermi interactions, in addition to the standard 4-Fermi interactions. The strengths of those higher-order Fermi interactions is determined so as not to spoil the saturation properties of nuclear matter. Among them, an interaction characterized by a product of four-quark current operators plays a special role to stabilize the stars over a large region of central baryon densities, although it has little effect on the maximum star masses.

The issue of cluster production in heavy-ion collisions is addressed in a new manner, by implementing cluster correlation into the quantum molecular dynamics (QMD) transport model. We demonstrate for the first time, the good potentialities of this popular transport approach in the unified description of light-cluster production including the deuteron, the triton, ${}^3\mathrm{He}$, and the $\alpha$ cluster in heavy-ion collisions at intermediate energies. Both the INDRA and FOPI experimental data of the yields of light clusters and the charge distributions of heavier fragments are reasonably reproduced in a unified manner. The effects of both the cluster binding energies and the Pauli repulsion are also shown to play crucial roles in the production of clusters.

We reexamined the electronic structure parameters used to interpret the hyperfine structure of neutral polonium. We used a computational scheme that treats relativistic and high-order electronic correlation effects within the coupled cluster with single, double, triple, and perturbative quadruple excitations (CCSDT(Q) method), as well as estimated the contribution of quantum electrodynamics and finite nuclear size effects. A systematic study of the uncertainty is carried out. This allowed us to obtain significantly refined values for the nuclear magnetic dipole and electric quadrupole moments of a wide range of odd-mass polonium isotopes. For ${}^{205}\mathrm{Po}$ and ${}^{207}\mathrm{Po}$ we extracted both the magnetic moment and the nuclear magnetization distribution parameter in a nuclear model-independent way. To assess the accuracy of the calculations, we also computed the ionization potential (IP), excitation energies (EEs) of the $6p^4{}^{1}D_2$ and $6p^{3}7s^1{}^{5}S_2$ electronic states, and the electronic $g_J$ factor in the same theoretical framework. A good agreement of the theory and experiment for IP, EEs, and $g_J$ confirms the reliability of the computational scheme and uncertainty estimation for the Po electromagnetic moments. We identify the $6p^4{}^{1}D_2$ electronic level as a potentially promising state for further studies of the nuclear moments of polonium isotopes.

Background: The isoscalar giant monopole resonance (ISGMR) splits into two peaks in prolately deformed nuclei. When a nucleus is triaxially deformed, a peak appears in the middle between the two peaks.

Purpose: We investigate the mechanism of the appearance of the middle peak in the ISGMR in triaxial nuclei.

Method: We perform the constrained Skyrme-Hartree-Fock-Bogoliubov (CHFB) calculation for arbitrary triaxial shapes in ${}^{100}\mathrm{Mo}$. We calculate the strength functions of the isoscalar monopole (ISM) and IS quadrupole modes on the CHFB states. Furthermore, we investigate vibrations of matter distributions in $x$, $y$, and $z$ directions induced by the external ISM field, with the $z$ axis being the longest axis of the triaxial shape.

Results: The middle peak in the ISM strength evolves from the triaxial degree $\gamma =0^{\circ }$ to ${60}^{\circ }$. This is because the difference between the vibration in the $x$ direction and that in the $y$ direction is evident with an increase in $\gamma$, and the quadrupole $K=2$ component of the induced density of the ISM at the middle peak increases as $\gamma$ increases, where $K$ denotes the $z$ component of the angular momentum. This property is also obtained in the unperturbed ISM strength without the residual fields.

Conclusions: The mixing between the monopole and quadrupole modes is primarily determined by the ground-state deformation. Therefore, the ISM strength of the middle peak becomes strong as the triaxial degree in the ground state increases.

Correlations involving the seven conserved quantities, namely energy, baryon number, electric charge, strangeness, and the three components of momentum, give rise to correlations in heavy-ion collisions. Through the utilization of a simple one-dimensional hydrodynamic model, we calculate the evolution of the entire $7\times 7$ matrix of correlations as a function of relative spatial rapidity. This comprehensive analysis accounts for finite baryon density, which results in off-diagonal correlations between the charge-related quantities and the energy-momentum quantities. These correlations in coordinate space are subsequently transformed into correlations in momentum space using statistical weighting. The entire matrix of correlations is revealed to be highly sensitive to the equation of state, viscosity, and diffusivity.

We have previously shown [R. Rizaldy, A. R. Alfarasyi, A. Sulaksono, and T. Sumaryada, Phys. Rev. C 100, 055804 (2019)] that Fermi-surface distortion can affect nuclear matter and neutron star (NS) properties within the relativistic mean-field formalism. However, our previous results had the caveat that the $k_f/M^{*}<1$ approximation was used. This approximation needs revision for high-density NS cases. This work proposes a more refined approximation in calculating the Fermi-surface distortion correction. We reinvestigate the consequences in nuclear and NS matter. The new expressions of the corresponding nucleon densities, energy density, and pressures are shown. The behavior of the predictions in high-density regions is studied. We found a better convergence of results for higher $\delta$ values than in the previous work. We also found that all recent experimental observations and other calculations constrain the acceptable value of $\delta$ to $\lesssim 0.1$. We also study the impact of Fermi-surface distortion on NS mass, radius, moment of inertia, and tidal deformability. The results are compared to the recent observation data. The impact of the anisotropy of acceptable $\delta$ values still does not profoundly impact a NS's mass and moment of inertia. However, we also observed a substantial effect in tidal deformation properties, such as $\mathrm{\Lambda }$ and $k_2$ parameters. Therefore, the signature of Fermi-surface distortion might be detected in observations of gravitational waves.

Two $0^{+}$ states at 1294.5 and 1774.0 keV, together with three $2^{+}$ and one $4^{+}$ levels, were identified or unambiguously spin-parity assigned for the first time in ${}^{100}\mathrm{Zr}$ utilizing $\gamma$-ray spectroscopy and $\gamma -\gamma$ angular correlation techniques with the Gammasphere spectrometer, following the ${\beta }^{-}$ decay of neutron-rich, mass-separated ${}^{100,100m}\mathrm{Y}$ isotopes. Comparisons with recent Monte Carlo shell-model calculations indicate that these two states are candidates for the bandhead of a sequence in a shape-coexisting spherical minimum predicted to be located around $\approx 1500$ keV. According to the measured relative $B{\left(E2\right)}_{\mathrm{relative}}$ transition probabilities, the $0_5^{+}$ state exhibits decay properties which more closely align with those predicted for a spherical shape, while the $0_4^{+}$ level is suggested to be associated with a weakly deformed shape similar to one related to the $0_2^{+}$ state.

Within the framework of the isospin-dependent quantum molecular dynamics model and statistical evaporation model, the production of neutron-deficient ${}^{245–250}\mathrm{Lr}$ isotopes is investigated. The fusion probability in the reaction ${}^{44}\mathrm{Ca}+{}^{209}\mathrm{Bi}$ is larger than that with ${}^{40}\mathrm{Ca}$ beam, especially at a lower incident energy and smaller impact parameter, which is attributed to a lower dynamical barrier in ${}^{44}\mathrm{Ca}+{}^{209}\mathrm{Bi}$. The neck between the projectile and target grows faster in the reaction with ${}^{44}\mathrm{Ca}$ beam, and the $N/Z$ ratio in the neck is larger, resulting in a lower dynamical barrier. Based on the fusion reactions of ${}^{40,44}\mathrm{Ca}+{}^{209}\mathrm{Bi}$ and ${}^{46,48}\mathrm{Ti}+{}^{203}\mathrm{Tl}$, we predicted six new Lr isotopes, ${}^{245–250}\mathrm{Lr}$, with the maximal evaporation residue cross sections of 3.5 fb, 69 pb, 0.2 nb, 0.4 nb, 1.7 nb, and 1.8 nb, respectively.

The properties of resonances in the ${}^{18}\mathrm{O}+\alpha$ interaction are important for analyses of astrophysical processes and for understanding of the development of the $\alpha$-cluster structure with addition of neutrons to 4N nuclei. Previous high-energy resolution measurements have not been treated using the contemporary $R$-matrix approach. We have performed an $R$-matrix analysis of the resonant data [D. Powers, J. K. Bair, J. L. C. Ford, Jr., and H. B. Willard, Phys. Rev. 134, B1237 (1964)] and obtained new data on 15 levels in the excitation region of 11.7–12.5 MeV ${}^{22}\mathrm{Ne}$. It appears that the model calculations did not predict the observed tendency in the ${}^{20–22}\mathrm{Ne}$ $\alpha$ clustering. This paper is the first step of our program of investigation of the ${}^{22}\mathrm{Ne}$ spectrum in resonant reactions.

Theoretical predictions for lepton-induced single-pion production (SPP) on ${}^{12}\mathrm{C}$ are revisited in order to assess the effect of different treatments of the current operator. On one hand we have the asymptotic approximation, which consists in replacing the particle four-vectors that enter in the operator by their asymptotic values, i.e., their values out of the nucleus. On the other hand we have the full calculation, which is a more accurate approach to the problem. We also compare with results in which the final nucleon is described by a relativistic plane wave, to rate the effect of the nucleon distortion. The study is performed for several lepton kinematics, reproducing the SPP contribution to the inclusive and semi-inclusive cross sections belonging to the low-$Q^2$ region (between 0.05 and 1 ${\mathrm{GeV}}^2$), which is of special interest in charged-current (CC) neutrino-nucleus $1\pi$ production. The results of the SPP contribution to the inclusive electron cross section are compared with experimental data. We find nontrivial corrections comparable in size with the effect of the nucleon distortion, namely, corrections up to 6%, either increasing or diminishing the asymptotic prediction, and a shift of the distributions towards higher energy transfer. For the SPP contribution to the semi-inclusive cross section, we observe the correction to be prominent mainly at low values of the outgoing nucleon kinetic energy. Finally, for CC neutrino-induced $1{\pi }^{+}$ production, we find a reduction at low $Q^2$ with respect to both the plane-wave approach and the asymptotic case.

The production of $\eta$ and ${\eta }^{\prime }$ mesons is studied in proton-proton and proton-lead collisions collected with the LHCb detector. Proton-proton collisions are studied at center-of-mass energies of $5.02$ and $13\mathrm{TeV}$ and proton-lead collisions are studied at a center-of-mass energy per nucleon of $8.16\mathrm{TeV}$. The studies are performed in center-of-mass (c.m.) rapidity regions $2.5<y_{\mathrm{c}.\mathrm{m}.}<3.5$ (forward rapidity) and $-4.0<y_{\mathrm{c}.\mathrm{m}.}<-3.0$ (backward rapidity) defined relative to the proton beam direction. The $\eta$ and ${\eta }^{\prime }$ production cross sections are measured differentially as a function of transverse momentum for $1.5<p_{\mathrm{T}}<10\mathrm{GeV}$ and $3<p_{\mathrm{T}}<10\mathrm{GeV}$, respectively. The differential cross sections are used to calculate nuclear modification factors. The nuclear modification factors for $\eta$ and ${\eta }^{\prime }$ mesons agree at both forward and backward rapidity, showing no significant evidence of mass dependence. The differential cross sections of $\eta$ mesons are also used to calculate $\eta /{\pi }^0$ cross-section ratios, which show evidence of a deviation from the world average. These studies offer new constraints on mass-dependent nuclear effects in heavy-ion collisions, as well as $\eta$ and ${\eta }^{\prime }$ meson fragmentation.

The search for the chiral magnetic effect (CME) in relativistic heavy-ion collisions helps us understand the $\mathcal{CP}$ symmetry breaking in strong interactions and the topological nature of the QCD vacuum. Since the background and signal of the CME have different correlations with the spectator and participant planes, a two-plane method has been proposed to extract the fraction of the CME signal inside the CME observable of $\mathrm{\Delta }\gamma$ from the experimental measurements relative to the two planes. Using a multiphase transport model with different strengths of the CME, we reexamine the two-plane method in isobar collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The ratios of the CME signals and the elliptic flow backgrounds relative to the two different planes are found to be different, which is inconsistent with the assumptions made in the current experimental measurements. This difference arises from the decorrelation effect of the chiral magnetic effect relative to the spectator and participant planes caused by final-state interactions. Our finding suggests that the current experimental measurements may overestimate the fraction of the CME signal in the CME observable in the final state of relativistic heavy-ion collisions.

In this work, we evaluate the recoil corrections to the correlation coefficients in the neutron ${\beta }^{-}$ decay with polarized neutron and polarized electron, up to order $O\left(m_n^{-2}\right)$, where $m_n$ represents the mass of neutron. In our calculations, we express the mass of proton $m_p$ in terms of $m_n$ and other small quantities to ensure that only one larger parameter, $m_n$, remains in the differential cross section. Subsequently, we expand the differential cross section on $m_n^{-1}$, and finally integrate the solid angles of the antineutrino to obtain the analytic expressions for the angular correlation coefficients. Comparing the analytic results to those in a previous study [Ivanov, Hollwieser, Troitskaya, Wellenzohn, and Berdnikov, Phys. Rev. C 95, 055502 (2017); Phys. Rev. C 104, 069901(E) (2021)], we find that, at order $O\left(m_n^{-1}\right)$, three of the results are consistent, while two differ slightly. In addition, the contributions at order $O\left(m_n^{-2}\right)$ are presented when considering a general form of $Wnp$ interactions. Numerical results show that contributions from order $O\left(m_n^{-2}\right)$ and additional form factors of $Wnp$ interactions are required to achieve a precision of ${10}^{-5}$.

We investigate the stability and softness of nuclei against quadrupole, octupole, and hexadecapole deformation. By applying the spherical Skyrme-force Hartree-Fock Bardeen-Cooper-Schrieffer quasiparticle random phase approximation, we diagnose ground-state deformation when imaginary solutions are obtained, i.e., the spherical ground state collapses. We also calculate the multipole polarizability in spherical nuclei with no collapse, as a measure of softness. This numerically light and theoretically sound method is found able to capture deformation patterns across the nuclide chart. The connection between the intrinsic shape of nuclei and the dynamics of their low-lying collective states is established and the role of shell structure is discussed.