Employing recently proposed metamodeling for the nucleonic matter equation of state, we analyze neutron star global properties such as masses, radii, momentum of inertia, and others. The impact of the uncertainty on empirical parameters on these global properties is analyzed in a Bayesian statistical approach. Physical constraints, such as causality and stability, are imposed on the equation of state and different hypotheses for the direct Urca (dUrca) process are investigated. In addition, only metamodels with maximum masses above $2M_{\odot }$ are selected. Our main results are the following: the equation of state exhibits a universal behavior against the dUrca hypothesis under the condition of charge neutrality and $\beta$ equilibrium; neutron stars, if composed exclusively of nucleons and leptons, have a radius of $12.7\pm 0.4$ km for masses ranging from 1 up to $2M_{\odot }$; a small radius lower than 11 km is very marginally compatible with our present knowledge of the nuclear empirical parameters; and finally, the most important empirical parameters which are still affected by large uncertainties and play an important role in determining the radius of neutrons stars are the slope and curvature of the symmetry energy ($L_{\mathrm{sym}}$ and $K_{\mathrm{sym}}$) and, to a lower extent, the skewness parameters ($Q_{\mathrm{sat}/\mathrm{sym}}$).

The tilted-axis cranking model based on covariant density functional theory is used to study the candidate antimagnetic rotation (AMR) bands in ${}^{101,102,103,104}\mathrm{Pd}$. The experimental energy spectra and $B\left(E2\right)$ values are reproduced well in the self-consistent and microscopic calculations. By investigating microscopically the composition and orientation of angular momentum, an “umbrella”-like antimagnetic rotation (UAMR) mode resulting from the coupling of four $g_{9/2}$ proton holes to neutron particles is clearly illustrated for the first time.

Lifetime measurements have been performed using the ${}^{98}\mathrm{Mo}$(${}^{86}\mathrm{Kr},4n$)${}^{180}\mathrm{Pt}$ reaction at a beam energy of 380 MeV, and the recoil distance Doppler-shift method. In a second experiment the ${}^{168}\mathrm{Yb}$(${}^{16}\mathrm{O},4n$)${}^{180}\mathrm{Pt}$ reaction at a beam energy of 88 MeV using the Ge-gated $\gamma -\gamma$ fast timing technique was used to determine lifetimes. Lifetimes of the four lowest yrast states of ${}^{180}\mathrm{Pt}$ have been determined. The experimental data are compared to calculations within the framework of the interacting boson model and the general collective model. Both models predict a deformed ground state and are consistent with all the remaining experimental results.

In this paper, we study pair correlations in low-lying $T=0$ states for two typical cases of odd-odd $N=Z$ nuclei. The first case is six nucleons in a single $j=9/2$ shell, for which we study the $S$-broken-pair approximation, the isoscalar spin-1 pair condensation, and the isoscalar spin-aligned pair condensation, with schematic interactions. In the second case, we study pair approximations and correlation energies for ${}^{22}\mathrm{Na}$, ${}^{34}\mathrm{Cl}$, ${}^{46}\mathrm{V}$, ${}^{62}\mathrm{Ga}$, and ${}^{94}\mathrm{Ag}$ in multi-$j$ shells with effective interactions. A few $T=0$ states are found to be well represented by isoscalar nucleon pairs. The isoscalar spin-aligned pairs play an important role for the yrast $T=0$ states with $I\sim 2j$ and $I\sim I_{\max }$ in ${}^{22}\mathrm{Na}$, ${}^{46}\mathrm{V}$, and ${}^{94}\mathrm{Ag}$. The overlap between the isoscalar $\mathcal{J}=1$ pair wave function and the shell-model wave function is around 0.5 for the $I=1,3$ states of ${}^{34}\mathrm{Cl}$ and the $I=1$ state of ${}^{94}\mathrm{Ag}$. The $I=9$ state of ${}^{62}\mathrm{Ga}$ is very well described by the isoscalar $\mathcal{J}=3$ pair condensation. The broken-pair approximation (which is similar to the 2-quasiparticle excitation of the isovector pair condensation) is appropriate for quite few states, such as the $I=1-3$ states of ${}^{34}\mathrm{Cl}$ and the $I=5$ state of ${}^{62}\mathrm{Ga}$. The correlation energies are presented in this paper. It is noted that the picture based on nucleon-pair wave functions is not always in agreement with the picture based on correlation energies.

The odd-even parity splittings in low-lying parity-doublet states of atomic nuclei with octupole correlations have usually been interpreted as rotational excitations on top of octupole vibration in the language of collective models. In this paper, we report a deep analysis of the odd-even parity splittings in the parity-doublet states of neutron-rich Ba isotopes around neutron number $N=88$ within a full microscopic framework of beyond-mean-field multireference covariant energy density functional theory. The dynamical correlations related to symmetry restoration and quadrupole-octupole shape fluctuation are taken into account with a generator coordinate method combined with parity, particle-number, and angular-momentum projections. We show that the behavior of odd-even parity splittings is governed by the interplay of rotation, quantum tunneling, and shape evolution. Similar to ${}^{224}\mathrm{Ra}$, a picture of rotation-induced octupole shape stabilization in the positive-parity states is exhibited in the neutron-rich Ba isotopes.

A spatially periodic longitudinal wave is considered in relativistic dissipative hydrodynamics. At sufficiently small wave amplitudes, an analytic solution is obtained in the linearized limit of the macroscopic conservation equations within the first- and second-order relativistic hydrodynamics formulations. A kinetic solver is used to obtain the numerical solution of the relativistic Boltzmann equation for massless particles in the Anderson-Witting approximation for the collision term. It is found that, at small values of the Anderson-Witting relaxation time $\tau$, the transport coefficients emerging from the relativistic Boltzmann equation agree with those predicted through the Chapman-Enskog procedure, while the relaxation times of the heat flux and shear pressure are equal to $\tau$. These claims are further strengthened by considering a moment-type approximation based on orthogonal polynomials under which the Chapman-Enskog results for the transport coefficients are exactly recovered.

Ab initio calculations of the Gamow-Teller (GT) matrix elements in the $\beta$ decays of ${}^6\mathrm{He}$ and ${}^{10}\mathrm{C}$ and electron captures in ${}^7\mathrm{Be}$ are carried out using both variational and Green's function Monte Carlo wave functions obtained from the Argonne $v_{18}$ two-nucleon and Illinois-7 three-nucleon interactions, and axial many-body currents derived from either meson-exchange phenomenology or chiral effective field theory. The agreement with experimental data is excellent for the electron captures in ${}^7\mathrm{Be}$, while theory overestimates the ${}^6\mathrm{He}$ and ${}^{10}\mathrm{C}$ data by $\sim 2\%$ and ∼10%, respectively. We show that for these systems correlations in the nuclear wave functions are crucial to explaining the data, while many-body currents increase by ∼2–3% the one-body GT contributions.

We construct a nuclear interaction in chiral effective field theory with explicit inclusion of the $\mathrm{\Delta }$-isobar $\mathrm{\Delta }\left(1232\right)$ degree of freedom at all orders up to next-to-next-to-leading order (NNLO). We use pion-nucleon ($\pi N$) low-energy constants (LECs) from a Roy-Steiner analysis of $\pi N$ scattering data, optimize the LECs in the contact potentials up to NNLO to reproduce low-energy nucleon-nucleon scattering phase shifts, and constrain the three-nucleon interaction at NNLO to reproduce the binding energy and point-proton radius of ${}^4\mathrm{He}$. For heavier nuclei we use the coupled-cluster method to compute binding energies, radii, and neutron skins. We find that radii and binding energies are much improved for interactions with explicit inclusion of $\mathrm{\Delta }\left(1232\right)$, while $\mathrm{\Delta }$-less interactions produce nuclei that are not bound with respect to breakup into $\alpha$ particles. The saturation of nuclear matter is significantly improved, and its symmetry energy is consistent with empirical estimates.

We use the superfluid tunneling model (STM) to calculate the half-lives of ground-state $\alpha$ decays of even-even superheavy nuclei (SHN) with $Z\ge 100$. The experimental data are reproduced to accuracies comparable to other contemporary models of $\alpha$ decay of SHN. We apply the STM to the case of the $\alpha$ decaying high-K isomers identified in the decay chains of ${}^{270}\mathrm{Ds}$. By accounting for the $\alpha$-decay Q values, $Q_{\alpha }$, the angular momentum difference between initial and final states, L, and a reduction in the pairing gap, Δ, we are able to reproduce the observed $\alpha$ decay of the isomers, including the unusual competition between $L\approx 10$ and $L\approx 0\alpha$ branches seen for the K isomer in ${}^{270}\mathrm{Ds}(Z=110)$.

The lowest positive- and negative-parity bands of ${}^{20}\mathrm{Ne}$ and neutron-rich even-even Ne isotopes are investigated using a theoretical framework based on energy density functionals. Starting from a self-consistent relativistic Hartree-Bogoliubov calculation of axially symmetric and reflection-asymmetric deformation energy surfaces, the collective symmetry-conserving states are built using projection techniques and the generator coordinate method. Overall a good agreement with the experimental excitation energies and transition rates is obtained. In particular, the model provides an accurate description of the excitation spectra and transition probabilities in ${}^{20}\mathrm{Ne}$. The contribution of cluster configurations to the low-energy states is discussed, as well as the transitional character of the ground state. The analysis is extended to ${}^{22}\mathrm{Ne}$ and the shape-coexisting isotope ${}^{24}\mathrm{Ne}$, and to the drip-line nuclei ${}^{32}\mathrm{Ne}$ and ${}^{34}\mathrm{Ne}$. The role of valence neutrons in the formation of molecular-type bonds between clusters is discussed.

The quark rearrangement model for baryon-antibaryon annihilation and reproduction ($B\overline{B}\leftrightarrow 3M$)—incorporated in the Parton-Hadron-String Dynamics (PHSD) transport approach—is extended to the strangeness sector. A derivation of the transition probabilities for the three-body processes is presented and a strangeness suppression factor for the invariant matrix element squared is introduced to account for the higher mass of the strange quark compared to the light up and down quarks. In simulations of the baryon-antibaryon annihilation and reformation in a box with periodic boundary conditions, we demonstrate that our numerical implementation fulfills detailed balance on a channel-by-channel basis for more than 2000 individual $2\leftrightarrow 3$ channels. Furthermore, we study central Pb+Pb collisions within PHSD from $11.7A\mathrm{GeV}$ to $158A\mathrm{GeV}$ and investigate the impact of the additionally implemented reaction channels in the strangeness sector. We find that the new reaction channels have a visible impact essentially only on the rapidity spectra of antibaryons. The spectra with the additional channels in the strangeness sector are closer to the experimental data than without for all antihyperons. Due to the chemical redistribution between baryons-antibaryons and mesons we find a slightly larger production of antiprotons thus moderately overestimating the available experimental data. We additionally address the question if the antibaryon spectra (with strangeness) from central heavy-ion reactions at these energies provide further information on the issue of chiral symmetry restoration and deconfinement. However, by comparing transport results with and without partonic phase as well as including and excluding effects from chiral symmetry restoration we find no convincing signals in the strange antibaryon sector for either transition due to the strong final-state interactions.

The $f_0\left(1500\right)$ meson resonance is one of several contenders to have significant mixing with the lightest glueball. This resonance is well established from several previous experiments. Here we present the first photoproduction data for the $f_0\left(1500\right)$ via decay into the $K_S^0{K}_S^0$ channel using the CLAS detector. The reaction $\gamma p\to f_{J}p\to K_S^0{K}_S^{0}p$, where $J=0,2$, was measured with photon energies from 2.7–5.1 GeV. A clear peak is seen at 1500 MeV in the background subtracted invariant mass spectra of the two kaons. This is enhanced if the measured four-momentum transfer to the proton target is restricted to be less than 1.0 ${\mathrm{GeV}}^2$. By comparing data with simulations, it can be concluded that the peak at 1500 MeV is produced primarily at low $t$, which is consistent with a $t$-channel production mechanism.

We investigate the high-temperature effect on the nuclear matter that consists of mixture of nucleons and all nuclei in the dense and hot stellar environment. The individual nuclei are described within the compressible-liquid-drop model that is based on Skyrme interactions for bulk energies and that takes into account modifications of the surface and Coulomb energies at finite temperatures and densities. The free-energy density is minimized with respect to the individual equilibrium densities of all heavy nuclei and the nuclear composition. We find that their optimized equilibrium densities become smaller and smaller at high temperatures because of the increase in thermal contributions to bulk free energies and the reduction of surface energies. The neutron-rich nuclei become unstable and disappear one after another at given temperatures. The calculations are performed for two sets of model parameters leading to different values of the slope parameter in the nuclear-symmetry energy. It is found that the larger slope parameter reduces the equilibrium densities and the melting temperatures. We also compare the proposed model with some other approaches and find that the mass fractions of heavy nuclei in the previous calculations that omit vaporization are underestimated at $T\lesssim 10$ MeV and overestimated at $T\gtrsim 10$ MeV. The further sophistication of calculations of nuclear vaporization and of light clusters would be required to construct the equation of state for explosive astrophysical phenomena.

The nodal structure of the density distributions of the single-particle states occupied in rod-shaped, hyper- and megadeformed structures of nonrotating and rotating $N\sim Z$ nuclei has been investigated in detail. The single-particle states with the Nilsson quantum numbers of the $\left[NN0\right]1/2$ (with $N$ from 0 to 5) and $[N,N-1,1]\mathrm{\Omega }$ (with $N$ from 1 to 3 and $\mathrm{\Omega }=1/2$, 3/2) types are considered. These states are building blocks of extremely deformed shapes in the nuclei with mass numbers $A\le 50$. Because of (near) axial symmetry and large elongation of such structures, the wave functions of the single-particle states occupied are dominated by a single basis state in cylindrical basis. This basis state defines the nodal structure of the single-particle density distribution. The nodal structure of the single-particle density distributions allows us to understand in a relatively simple way the necessary conditions for $\alpha$ clusterization and the suppression of the $\alpha$ clusterization with the increase of mass number. It also explains in a natural way the coexistence of ellipsoidal mean-field-type structures and nuclear molecules at similar excitation energies and the features of particle-hole excitations connecting these two types of the structures. Our analysis of the nodal structure of the single-particle density distributions does not support the existence of quantum liquid phase for the deformations and nuclei under study.

Structures of low-lying $0s$-orbit $\mathrm{\Lambda }$ states in $p$-shell $\mathrm{\Lambda }$ hypernuclei (${}_{\mathrm{\Lambda }}{}^{A}Z$) are investigated by applying microscopic cluster models for nuclear structure and a single-channel folding potential model for a $\mathrm{\Lambda }$ particle. For $A>10$ systems, the size reduction of core nuclei is small, and the core polarization effect is regarded as a higher-order perturbation in the $\mathrm{\Lambda }$ binding. The present calculation qualitatively describes the systematic trend of experimental data for excitation energy change from ${}^{A-1}Z$ to ${}_{\mathrm{\Lambda }}{}^{A}Z$, in $A>10$ systems. The energy change shows a clear correlation with the nuclear size difference between the ground and excited states. In ${}_{\mathrm{\Lambda }}{}^7\mathrm{Li}$ and ${}_{\mathrm{\Lambda }}{}^9\mathrm{Be}$, the significant shrinkage of cluster structures occurs consistently with the prediction of other calculations.

The depletion of the nuclear density at its center, called the nuclear bubble, is studied within the Skyrme Hartree-Fock mean field consistently incorporating the superfluid pairing. The latter is obtained within the finite-temperature Bardeen-Cooper-Schrieffer theory and within the approach using the exact pairing. The numerical calculations are carried out for ${}^{22}\mathrm{O}$ and ${}^{34}\mathrm{Si}$ nuclei, whose bubble structures, caused by a very low occupancy of the $2s_{1/2}$ level, were previously predicted at $T=0$. Among 24 Skyrme interactions under consideration, the MSk3 is the only one which reproduces the experimentally measured occupancy of the $2s_{1/2}$ proton level as well as the binding energy, and consequently produces the most pronounced bubble structure in ${}^{34}\mathrm{Si}$. As compared to the approaches employing the same BSk14 interaction, our approach with exact pairing predicts a pairing effect which is stronger in ${}^{22}\mathrm{O}$ and weaker in ${}^{34}\mathrm{Si}$. The increase in temperature depletes the bubble structure and completely washes it out when the temperature reaches a critical value, at which the factor measuring the depletion of the nucleon density vanishes.

Background: The formation of superheavy elements (SHEs) by fusion of two massive nuclei is severely inhibited by the competing quasifission process. Low excitation energies favor SHE survival against fusion-fission competition. In “cold” fusion with spherical target nuclei near ${}^{208}\mathrm{Pb}$, SHE yields are largest at beam energies significantly below the average capture barrier. In “hot” fusion with statically deformed actinide nuclei, this is not the case. Here the elongated deformation-aligned configurations in sub-barrier capture reactions inhibits fusion (formation of a compact compound nucleus), instead favoring rapid reseparation through quasifission.

Purpose: To determine the probabilities of fast and slow quasifission in reactions with prolate statically deformed actinide nuclei, through measurement and quantitative analysis of the dependence of quasifission characteristics at beam energies spanning the average capture barrier energy.

Methods: The Australian National University Heavy Ion Accelerator Facility and CUBE fission spectrometer have been used to measure fission and quasifission mass and angle distributions for reactions with projectiles from C to S, bombarding Th and U target nuclei.

Results: Mass-asymmetric quasifission occurring on a fast time scale, associated with collisions with the tips of the prolate actinide nuclei, shows a rapid increase in probability with increasing projectile charge, the transition being centered around projectile atomic number $Z_{\mathrm{P}}=14$. For mass-symmetric fission events, deviations of angular anisotropies from expectations for fusion fission, indicating a component of slower quasifission, suggest a similar transition, but centered around $Z_{\mathrm{P}}\sim 8$.

Conclusions: Collisions with the tips of statically deformed prolate actinide nuclei show evidence for two distinct quasifission processes of different time scales. Their probabilities both increase rapidly with the projectile charge. The probability of fusion can be severely suppressed by these two quasifission processes, since the sub-barrier heavy element yield is likely to be determined by the product of the probabilities of surviving each quasifission process.

In order to study the influence of the strong Coulomb and nuclear interactions on the dynamics of complete and incomplete fusion, we construct a new four-variable master equation (ME) so that the deformations as well as the nucleon transfer are viewed as consistently governed by MEs in the potential energy surface of the system. The calculated yields of quasifission fragments and evaporation residue cross section (ERCS) are in agreement with experimental data of hot fusion reactions. Comparing cross sections by theoretical results and experimental data, we find the improved dinuclear sysytem model also describes the transfer cross sections reasonably. The production cross sections of new neutron-rich isotopes are estimated by the multinucleon transfer reactions.

We investigate the freeze-out conditions of a particle in an expanding system of interacting particles in order to understand the productions of resonances, hadronic molecules, and light nuclei in heavy-ion collisions. Applying the kinetic freeze-out condition with explicit hydrodynamic calculations for the expanding hadronic phase to the daughter particles of $K^{*}$ mesons, we find that the larger suppression of the yield ratio of $K^{*}/K$ at the Large Hadron Collider (LHC) than at the Relativisitic Heavy Ion Collider (RHIC) compared to the expectations from the statistical hadronization model based on chemical freeze-out parameters reflects the lower kinetic freeze-out temperature at LHC than at RHIC. Furthermore, we point out that for the light nuclei or hadronic molecules that are bound, the freeze-out condition should be applied to the respective particle in the hadronic matter. It is then shown through the rate equation that when the nucleon and pion numbers are kept constant at the chemical freeze-out value during the hadronic phase, the deuteron number quickly approaches an asymptotic value that is close to the statistical model prediction at the chemical freeze-out point. We argue that the reduction seen in $K^{*}$ numbers is a typical result for a particle that has a large natural decay width decaying into daughter particles, while that for deuteron is typical for a stable hadronic bound state.

In collisions of identical nuclei at a given impact parameter, the number of nucleons participating in the overlap region of each nucleus can be unequal due to nuclear density fluctuations. The asymmetry due to the unequal number of participating nucleons, referred to as longitudinal asymmetry, causes a shift in the center-of-mass rapidity of the participant zone. The information of the event asymmetry allows us to isolate and study the effect of longitudinal asymmetry on rapidity distribution of final state particles. In a Monte Carlo Glauber model the average rapidity shift is found to be almost linearly related to the asymmetry. Using toy models, as well as Monte Carlo data for Pb-Pb collisions at 2.76 TeV generated with hijing, two different versions of ampt and dpmjet models, we demonstrate that the effect of asymmetry on final state rapidity distribution can be quantitatively related to the average rapidity shift via a third-order polynomial with a dominantly linear term. The coefficients of the polynomial are proportional to the rapidity shift with the dependence being sensitive to the details of the rapidity distribution. Experimental estimates of the spectator asymmetry through the measurement of spectator nucleons in a zero-degree calorimeter may hence be used to further constrain the initial conditions in ultra-relativistic heavy-ion collisions.