The effects of density dependence of the symmetry energy on the collective modes and dynamical instabilities of cold and warm nuclear and stellar matter are studied in the framework of relativistic mean-field hadron models. The existence of the collective isovector and possibly an isoscalar collective mode above saturation density is discussed. It is shown that soft equations of state do not allow for a high-density isoscalar collective mode; however, if the symmetry energy is hard enough, an isovector mode will not disappear at high densities. The crust-core transition density and pressure are obtained as a function of temperature for $\beta$-equilibrium matter with and without neutrino trapping. Estimations of the size of the clusters formed in the nonhomogeneous phase, as well as the corresponding growth rates and distillation effect, are made. It is shown that cluster sizes increase with temperature, that the distillation effect close to the inner edge of the crust-core transition is very sensitive to the symmetry energy, and that, within a dynamical instability calculation, the pasta phase exists in warm compact stars up to $10-12$ MeV.

The level structure of ${}^{26}\mathrm{Mg}$ near the neutron-separation energy, which is of interest for s-process nucleosynthesis, was studied at the High Intensity Gamma-Ray Source of the Triangle Universities Nuclear Laboratory using the method of nuclear resonance fluorescence. A nearly monoenergetic and linearly polarized $\gamma$-ray beam was used to scan the excitation energy range from $10.5$ to $11.7$ MeV. For the five states observed, the total widths and partial widths are determined. Precise measurement of these widths is necessary for the prediction of neutron production for the s-process.

The aim of this work is to calculate the transfer strengths to the excited $0^{+}$ states in ${}^{130,132,134}\mathrm{Ba}$ which have been identified in ($p,t$) reactions and to investigate their related properties. For this purpose, we have used a model Hamiltonian which includes monopole pairing, quadrupole-quadrupole, and spin-quadrupole interactions. The model Hamiltonian has been diagonalized with the random phase approximation (RPA). To investigate the general trend of the transfer strengths to the excited $0^{+}$ states, two-nucleon transition intensities relative to the transition to the ground state and their cumulative values have been calculated versus energy and compared with the data. The comparisons revealed that fairly good results for the distribution of the energies and the transfer strengths have been obtained. For almost all nuclei, the cumulative values of the transfer strengths were nicely predicted. Moreover, qualitatively, a parallel result that agrees with the data and the prediction of the O(6) limit of the IBM model which is a weak excitation for the first $0^{+}$ state and a strong one for the second $0^{+}$ state has been obtained for ${}^{130}\mathrm{Ba}$ and ${}^{132}\mathrm{Ba}$.

High-statistics measurements of differential cross sections and recoil polarizations for the reaction $\gamma p\to K^{+}{\Sigma }^0$ have been obtained using the CLAS detector at Jefferson Lab. We cover center-of-mass energies ($\sqrt{s}$) from 1.69 to 2.84 GeV, with an extensive coverage in the $K^{+}$ production angle. Independent measurements were made using the $K^{+}p{\pi }^{-}$($\gamma$) and $K^{+}p$(${\pi }^{-},\gamma$) final-state topologies, and were found to exhibit good agreement. Our differential cross sections show good agreement with earlier CLAS, SAPHIR, and LEPS results, while offering better statistical precision and a 300-MeV increase in $\sqrt{s}$ coverage. Above $\sqrt{s}\approx 2.5$ GeV, $t$- and $u$-channel Regge scaling behavior can be seen at forward and backward angles, respectively. Our recoil polarization ($P_{\Sigma }$) measurements represent a substantial increase in kinematic coverage and enhanced precision over previous world data. At forward angles, we find that $P_{\Sigma }$ is of the same order of magnitude but opposite sign as $P_{\Lambda }$, in agreement with the static SU(6) quark model prediction of $P_{\Sigma }\approx -P_{\Lambda }$. This expectation is violated in some mid- and backward-angle kinematic regimes, where $P_{\Sigma }$ and $P_{\Lambda }$ are of similar magnitudes but also have the same signs. In conjunction with several other meson photoproduction results recently published by CLAS, the present data will help constrain the partial-wave analyses being performed to search for missing baryon resonances.

We have investigated the zero-temperature equation of state (EoS) for infinite nuclear matter within the $(\sigma -\omega )$ model at all densities $n_{\mathrm{B}}$ and different proton-neutron asymmetry $\eta \equiv (N-Z)/A$. We have presented an analytical expression for the compression modulus and found that nuclear matter ceases to saturate at $\eta$ slightly larger than $0.8$. Afterward, we have developed an analytical method to determine the strong coupling constants from the EoS for isospin symmetric nuclear matter, which allow us to reproduce all the saturation properties with high accuracy. For various values of the nucleon effective mass and the compression modulus, we have found that the quartic self-coupling constant $G_4$ is negative, or positive and very large. Furthermore, we have demonstrated that it is possible (a) to investigate the EoS in terms of $n_{\mathrm{B}}$ and $\eta$; and (b) to reproduce all the known saturation properties without $G_4$. We have thus concluded that the latter is not necessary in the $(\sigma -\omega )$ model.

One-neutron knockout reactions from neutron-rich nuclei, with $Z=6-13$ and $N=8-22$, were studied at the Fragment Separator (GSI) at high beam energies, around 700 MeV/nucleon. Structural phenomena such as the formation of one-neutron halos in odd-mass carbon isotopes (${}^{15,17,19}\mathrm{C}$) will be discussed. In addition, one-neutron knockout measurements from ${}^{22}\mathrm{N}$ were carried out for the first time and demonstrate clearly the change from a $0d_{5/2}$ to a $1s_{1/2}$ orbital for the valence neutron, an effect that is expected above $N=14$ and that was also observed in ${}^{23}\mathrm{O}$ and ${}^{24}\mathrm{F}$. The possibility of an anomalous structure of ${}^{26}\mathrm{F}$, due to a significant $1s_{1/2}$ neutron admixture, will also be discussed in the light of the experimental data obtained in this work. Finally, the ground-state configuration of neutron-rich neon isotopes (${}^{24-28}\mathrm{Ne}$) was studied, providing new information in a region that is relatively close to the island of inversion.

The ${}^6\mathrm{He}+{}^{12}\mathrm{C}$ elastic scattering data at beam energies of $3,38.3$, and $41.6$ MeV/nucleon are studied utilizing the microscopic optical potentials obtained by a double-folding procedure and also by using those inherent in the high-energy approximation. The calculated optical potentials are based on the neutron and proton density distributions of colliding nuclei established in an appropriate model for ${}^6\mathrm{He}$ and obtained from the electron scattering form factors for ${}^{12}\mathrm{C}$. The depths of the real and imaginary parts of the microscopic optical potentials are considered as fitting parameters. At low energy the volume optical potentials reproduce sufficiently well the experimental data. At higher energies, generally, additional surface terms having the form of a derivative of the imaginary part of the microscopic optical potential are needed. The problem of ambiguity of adjusted optical potentials is resolved requiring the respective volume integrals to obey the determined dependence on the collision energy. Estimations of the Pauli blocking effects on the optical potentials and cross sections are also given and discussed. Conclusions on the role of the aforesaid effects and on the mechanism of the considered processes are made.

In the large ’t Hooft coupling limit, the hadronic size of baryon is small and the nucleon-nucleon potential is obtained from massless pseudoscalar exchanges and an infinite tower of spin-one mesons exchanges. In this article we use the holographic nucleon-nucleon interaction and obtain the corresponding potential and binding energy for deuteron and tritium nuclei. The obtained potentials are repulsive at short distances and clearly become zero by increasing the distance as we expected.

Lowest order and higher order QED calculations have been carried out for the RHIC high mass $e^{+}{e}^{-}$ pairs observed by PHENIX with single zero-degree-calorimeter triggers. The lowest order QED results for the experimental acceptance are about two standard deviations larger than the PHENIX data. Corresponding higher order QED calculations are within one standard deviation of the data.

The medium-spin structure of the nuclei ${}^{93}\mathrm{Rb}$ and ${}^{95}\mathrm{Rb}$ is studied following the neutron-induced fission of ${}^{235}\mathrm{U}$ at the PF1B neutron guide, using the FIFI spectrometer, and at the Lohengrin mass spectrometer of the Institut Laue-Langevin Grenoble. These nuclei, plus ${}^{91}\mathrm{Rb}$, are also studied following the spontaneous fission of ${}^{248}\mathrm{Cm}$ and ${}^{252}\mathrm{Cf}$ sources, using the EUROGAM-II and Gammasphere detector arrays, respectively. A high-spin isomeric state, with a half-life of 111(11) ns, is found in ${}^{93}\mathrm{Rb}$ at an excitation energy of 4422.4 keV, which most likely corresponds to the fully aligned $[\pi (g_{9/2})\otimes \nu (g_{7/2}{h}_{11/2})]{}_{{27/2}^{-}}$ configuration. An analogous configuration is proposed for the 5297.9-keV level observed in ${}^{91}\mathrm{Rb}$. A new $E3$ decay branch of the 1133.9-keV isomer in ${}^{91}\mathrm{Rb}$ is found, for which the rather low transition rate of $B(E3)=3.8(10)$ W.u. is determined. The energy of the isomeric state of ${}^{95}\mathrm{Rb}$ is now proposed to be at 810.6 keV, with a spin of ($9/2^{+}$), and its half-life determined to be $T_{1/2}=94(7)$ ns. A cascade of prompt transitions is observed on top of the 810.6-keV isomer in ${}^{95}\mathrm{Rb}$. The near-yrast structures of ${}^{91}\mathrm{Rb}$, ${}^{93}\mathrm{Rb}$, and ${}^{95}\mathrm{Rb}$ are compared to the results of shell-model calculations, which support the proposed $27/2^{-}$ interpretation of states in ${}^{91}\mathrm{Rb}$ and ${}^{93}\mathrm{Rb}$. An analogous $27/2^{-}$ state is expected to occur in ${}^{95}\mathrm{Rb}$, as a long-lived isomer at 3.24 MeV. No such isomeric decay could be observed in a measurement using the Lohengrin spectrometer, which shows that, if it exists, its population, following the fission of ${}^{235}\mathrm{U}$, is at least four times lower than that of the analogous $27/2^{-}$ isomer in ${}^{97}\mathrm{Y}$.

Excited states in ${}^{192}\mathrm{Pt}$ and ${}^{194}\mathrm{Pt}$ have been studied with high-energy resolution, in the ($p,t$) reaction, by using the Q3D magnetic spectrograph at the Munich MP tandem accelerator. Outgoing tritons were recorded at laboratory angles sensitive to the unique shape of the $L=0$ angular distribution. Sets of previously unknown $0^{+}$ states were identified up to an energy of $~3\hspace{0.5em}\mathrm{MeV}$. The $0^{+}$ states in ${}^{192,194}\mathrm{Pt}$ are discussed in the context of the evolution of intruder states and shape coexistence in the light Pt isotopes.

A new algorithm for calculating the spin- and parity-dependent shell-model nuclear level densities using the moments method in the proton-neutron formalism is presented. A new, parallelized code based on this algorithm was developed and tested using up to 4000 cores for a set of nuclei from the $\mathit{sd}$-, $\mathit{pf}$-, and $\mathit{pf}+g_{9/2}$-model spaces. By comparing the nuclear level densities at low excitation energy for a given nucleus calculated in two model spaces, such as $\mathit{pf}$ and $\mathit{pf}+g_{9/2}$, one can estimate the ground-state energy in the larger model space, which is not accessible to direct shell-model calculations due to the unmanageable dimension. Examples for the ground-state energies of for ${}^{64}\mathrm{Ge}$ and ${}^{68}\mathrm{Se}$ in the $\mathit{pf}+g_{9/2}$ model space are presented.

Differential scattering cross-section data have been measured at 43 angles from ${11}^{°}$ to ${160}^{°}$ for 37-MeV neutrons incident on ${}^{209}\mathrm{Bi}$. The primary motivation for the measurements is to address the scarcity of neutron scattering data above 30 MeV and to improve the accuracy of optical-model predictions at medium neutron energies. The high-statistics measurements were conducted at the China Institute of Atomic Energy using the ${}^3\mathrm{H}$($d,n$)${}^4\mathrm{He}$ reaction as the neutron source, a pulsed deuteron beam, and time-of-flight (TOF) techniques. Within the resolution of the TOF spectrometer, the measurements included inelastic scattering components. The sum of elastic and inelastic scattering cross sections was computed in joint optical-model and distorted-wave Born approximation calculations under the assumption of the weak particle-core coupling. The results challenge predictions from well-established spherical optical potentials. Good agreement between data and calculations is achieved at 37 MeV provided that the balance between surface and volume absorption in a recent successful model [A. J. Koning and J. P. Delaroche, Nucl. Phys. A 713, 231 (2003)] is modified, thus suggesting the need for global optical-model improvements at medium neutron energies.

We study the dynamical response of the ${}^{16}\mathrm{O}$ nucleus to an incident antiproton using the Giessen Boltzmann-Uehling-Uhlenbeck microscopic transport model with relativistic mean fields. A special emphasis is put on the possibility of a dynamical compression of the nucleus induced by the moving antiproton. Realistic antibaryon coupling constants to the mean meson fields are chosen in accordance with empirical data. Our calculations show that an antiproton embedded in the nuclear interior with momentum less than the nucleon Fermi momentum may create a locally compressed zone in the nucleus with a maximum density of about twice the nuclear saturation density. To evaluate the probability of the nuclear compression in high-energy $\mathrm{p̄}$-nucleus collisions, we adopt a two-stage scheme. This scheme takes into account the antiproton deceleration due to the cascade of $\mathrm{p̄}N$ rescatterings inside the nucleus (first stage), as well as the nuclear compression by the slow antiproton before its annihilation (second stage). With our standard model parameters, the fraction of $\mathrm{p̄}$ annihilation events in the compressed zone is about ${10}^{-5}$ for ${\mathrm{p̄}}^{16}$O collisions at $p_{\mathrm{lab}}=3–10$ GeV/$c$. Finally, possible experimental triggers aimed at selecting such events are discussed.

The high-resolution, deflection-type mass spectrometer, Manitoba II, has been used to determine directly the mass difference ${}^{136}\mathrm{Xe}-{}^{136}\mathrm{Ba}$ to be 2639.6 (0.6) $\mu$u, giving ${\mathrm{Q}}_{\beta \beta }$ $=2458.7$ (0.6) keV.

We generalize a “one-eigenstate” version of the density square root theorem to the case of densities coming from eigenmixture density operators. The generalization is of a special interest for the radial density functional theory (RDFT) for nuclei, a consequence of the rotational invariance of the nuclear Hamiltonian; when nuclear ground states have a finite spin, the RDFT uses eigenmixture density operators to simplify predictions of ground-state energies into one-dimensional, radial calculations. We also study Schrödinger equations governing spin eigendensity matrices.

The observed $p_T$ dependence of nuclear effects for $J/\Psi$ produced in heavy-ion collisions at Brookhaven’s Relativistic Heavy-Ion Collider (RHIC) might look puzzling, because the nuclear suppression seems to fade at large $p_T$. We explain this by the interplay of three mechanisms: (i) attenuation of $J/\Psi$ in the hot medium created in the nuclear collision; (ii) initial-state shadowing of charmed quarks and attenuation of a $\mathrm{c̄}c$ dipole propagating through the colliding nuclei; (iii) a strong Cronin effect for $J/\Psi$ caused by saturation of gluons in the colliding nuclei. All three effects are well under control and calculated in a parameter-free way, except for the transport coefficient ${\mathrm{q̂}}_0$ characterizing the medium. This is adjusted to the $J/\Psi$ data and found to be in good agreement with the pQCD prediction, but more than an order of magnitude smaller than what was extracted from jet quenching data within the energy loss scenario.

We investigate how the neutron drip line is related to the density dependence of the symmetry energy by using a macroscopic nuclear model that allows us to calculate nuclear masses in a way that is dependent on the equation of state of asymmetric nuclear matter. The neutron drip line obtained from these masses is shown to appreciably shift to a neutron-rich side in a nuclear chart as the density derivative of the symmetry energy increases. Such a shift is clearly seen for light nuclei, a feature coming mainly from the surface property of neutron-rich nuclei.

Naive dimensional analysis based on chiral effective theory, when adapted to nuclear energy density functionals, prescribes natural units and a hierarchy of contributions that could be used to constrain fits of generalized functionals. By applying these units, a large sample of Skyrme parametrizations is examined for naturalness, which is signaled by dimensionless coupling constants of order one. The bulk of the parameters are found to be natural, with an underlying scale consistent with other determinations. Significant deviations from unity are associated with deficiencies in the corresponding terms of particular functionals or with an incomplete optimization procedure.