Spectroscopic factors derived from direct capture studies are systematically compared to those obtained from transfer reaction experiments and from shell model calculations for the $\mathrm{A}=16–32$ target mass region. The direct proton capture and proton transfer spectroscopic factors are obtained in the present work from a reanalysis of literature data by using the same bound state potential parameters. Our direct capture spectroscopic factors differ significantly from the values originally reported in the literature. The sensitivity of the direct capture cross section to different choices for the scattering potential is explored. We find evidence that spectroscopic factors obtained from direct capture studies are as reliable as those extracted from transfer measurements if the (direct capture) radial scattering wave function is calculated with a zero nuclear scattering potential instead of the common choice of a hard-sphere potential.

The discovery of a set of analytic solutions to describe nuclei at the critical point of spherical-deformed phase transitions has led to an increased interest in the properties of $0^{+}$ excited states. This idea provides the motivation for the present investigation to determine sets of interacting boson model (IBA) parameters that reproduce the properties of all low-lying, positive-parity excitations, including the first excited $0^{+}$ state, for a wide range of even-even, collective nuclei. Detailed fits of isotopic chains in the rare-earth region are shown to reproduce the energies of the positive-parity states and to provide a reasonable description of their transition matrix elements. Two neutron separation energies, isomer shifts, and isotope shifts are also described using a truncated IBA-1 Hamiltonian. A proposed set of polar coordinates allows for a mapping of these parameters into the IBA symmetry triangle and a comparison of trajectories for different isotopic chains.

Within Bombaci’s phenomenological single-nucleon potential model we study the neutron-proton effective mass splitting $m_n^{*}\text{−}{m}_p^{*}$ in neutron-rich matter. It is shown that an effective mass splitting of $m_n^{*}<m_p^{*}$ leads to a symmetry potential that is inconsistent with the energy dependence of the Lane potential constrained by the nucleon-nucleus scattering experimental data.

In this work we calculate the meson loop effects on the pion electromagnetic form factor and perform a comparison with experimental data. We show that, even though the meson cloud is not the only nonperturbative process to be considered, its contribution is significant.

With a simplified model in the Hartree-Fock-Bogoliubov (HFB) approximation, the behavior of weakly bound $s_{1∕2}$ neutrons in the many-body pair correlation is studied by solving the HFB equation in coordinate space with the correct asymptotic boundary conditions. It is shown that in one-neutron pickup reactions on the even-even neutron-drip-line nuclei, which contain loosely bound $s_{1∕2}$ neutrons, the strength of the $s_{1∕2}$ neutron can appear both at a discrete state and in the low-energy continuum spectra, with comparable strength. When there is no weakly bound discrete state, the continuum spectra may exhibit a sharp peak just above $E_x=\mid \lambda \mid$, which originates from the resonantlike behavior of the upper component of the HFB radial wave function, $u_{s1∕2}\left(E_{qp},r\right)$. This resonantlike behavior may be directly observed as an $s$-wave resonance close to $E_x=\mid \lambda \mid$ in neutron-scattering experiments on those nuclei. It is also shown that a very large root-mean-square radius of loosely bound $s_{1∕2}$ neutrons may appear also in the presence of many-body pair correlation, since the effective pair gap in weakly bound neutron orbits with low $\ell$ values is much reduced.

We study the low-lying collective excitation spectra of the neutron-deficient lead isotopes ${}^{182–194}\mathrm{Pb}$ by performing a configuration mixing of angular momentum and particle-number projected self-consistent mean-field states. The same effective interaction is used to generate the mean-field states and for the configuration mixing. We choose the Skyrme interaction SLy6 supplemented by a density-dependent zero-range pairing force. Our study supports the interpretation of the excitation spectra made on the grounds of more schematic models in terms of coexisting spherical, oblate, prolate, and superdeformed prolate structures. The model qualitatively reproduces the variation of the spectra with neutron number. Our results for $E0$ and $E2$ transition probabilities are compared with the few existing experimental data. Finally, we predict the presence of superdeformed bands at low excitation energy in the most neutron-deficient isotopes.

It has recently been suggested that the quark-gluon plasma formed in heavy-ion collisions behaves as a nearly ideal fluid. That behavior may be understood if the quark and antiquark mean free paths are very small in the system, leading to a “sticky molasses” description of the plasma, as advocated by the Stony Brook group. This behavior may be traced to the fact that there are relatively low-energy $q\overline{q}$ resonance states in the plasma leading to very large scattering lengths for the quarks. These resonances have been found in a lattice simulation of QCD using the maximum entropy method (MEM). We have used a chiral quark model, which provides a simple representation of effects due to instanton dynamics, to study the resonances obtained using the MEM scheme. In the present work we use our model to study the optical potential of a quark in the quark-gluon plasma and calculate the quark mean free path. Our results represent a specific example of the dynamics of the plasma as described by the Stony Brook group.

The low-lying levels in ${}^{59}\mathrm{Cr}$ have been studied with the ${}^{13}\mathrm{C}\left({}^{48}\mathrm{Ca},2p\right)$ reaction at a beam energy of $130\mathrm{MeV}$. Data on ${}^{59}\mathrm{Mn}$, produced via the $pn$-evaporation channel, have set limits on the spin of the ground state in ${}^{59}\mathrm{Cr}$ and enabled some spin-parity assignments of excited states to be made. The structure obtained in this study is clearly inconsistent with results of shell-model calculations within the full $fp$ shell and requires inclusion of the $\nu g_{9∕2}$ orbital. The sequence of states is understood within Nilsson model calculations assuming a moderate oblate ground-state deformation.

A new semiempirical model called FRANG for calculation of fragment emission angles in light and heavy ion fragmentation reactions was developed. Contributions from both central and peripheral collisions were investigated, where fragmentation occurs due to nuclear and Coulomb interaction, respectively. For central collisions the reaction was described by a two step abrasion-ablation model, where collision parameters were determined from a simple geometrical model. The fragment emission angles were calculated using a parametrization of longitudinal momentum loss and transverse momentum uptake in the collision of projectile and target atom. For peripheral collisions the Coulomb excitation of nucleon vibration resonances and subsequent decay into fragments was taken into account. Fragment emission angles were calculated from deflection in the electric field and from the amplitude of vibrations in excited nuclear states. The modeled emission angles were in accordance with the experimental values for most projectile-target systems examined and compared. It was established that the model very well reproduces the experimental results in the energy region $<200\mathrm{MeV}∕\text{nucleon}$, despite its simplicity, and can be successfully employed in several applications. The model is estimated to be valid in the energy range from a few $10\mathrm{MeV}∕\text{nucleon}$ up to few $100\mathrm{MeV}∕\text{nucleon}$.

The relation between the superdeformed band of ${}^{32}\mathrm{S}$ and ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ molecular bands is studied by the deformed-basis antisymmetrized molecular dynamics with the Gogny D1S force. It is found that the obtained superdeformed band members of $\mathrm{S}$ have a considerable amount of the ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ component. Above the superdeformed band, we have obtained two excited rotational bands which have more prominent character of the ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ molecular band. These three rotational bands are regarded as a series of ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ molecular bands which were predicted by using the unique ${}^{16}\mathrm{O}\text{−}{}^{16}\mathrm{O}$ optical potential. As the excitation energy and principal quantum number of the relative motion increase, the ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ cluster structure becomes more prominent but at the same time, the band members are fragmented into several states.

We calculate microscopically the equation of state of the drip phase of neutron-star matter. Proton-shell effects are shown to persist, at zero temperature, beyond the neutron drip line, with magic numbers at $Z=8$, 14, 20, 28, 38, 50, 82, 92, and 114. The implications of these shell effects on the equilibrium composition of the Wigner-Seitz cells in this phase are discussed. We find that this composition depends strongly on the force chosen, according to the neutron-matter properties at subnuclear densities.

A semimicroscopic approach based on both the continuum random-phase-approximation method and a phenomenological treatment of the spreading effect is extended and applied to describe the main properties (particle-hole strength distribution, energy-dependent transition density, partial direct-nucleon-decay branching ratios) of the isoscalar giant dipole, second monopole, and second quadrupole resonances. The abilities of the approach are checked by description of the gross properties of the main-tone resonances. Calculation results obtained for the resonances in a few singly- and doubly-closed-shell nuclei are compared with available experimental data.

The ${}^{170,171}\mathrm{Au}$ isotopes were produced in the fusion-evaporation reaction of a ${}^{78}\mathrm{Kr}$ ion beam with a ${}^{96}\mathrm{Ru}$ target. For ${}^{170}\mathrm{Au}$ the proton and $\alpha$ emission from the ground state were observed for the first time and the decay of the isomeric state was measured with improved accuracy. In addition, the decay of ${}^{171}\mathrm{Au}$ was measured with high statistics. A new $\alpha$-emitting nucleus ${}^{171}\mathrm{Hg}$ and the previously known ${}^{172}\mathrm{Hg}$ and ${}^{167,168,169,170}\mathrm{Pt}$ isotopes were also studied. The ground-state proton emission was identified for a new proton emitter ${}^{176}\mathrm{Tl}$ using the fusion-evaporation reaction of ${}^{78}\mathrm{Kr}$ ions with a ${}^{102}\mathrm{Pd}$ target. The previously known proton emitter ${}^{177}\mathrm{Tl}$ and $\alpha$-decaying nucleus ${}^{173}\mathrm{Hg}$ were also identified in this reaction. The fusion products were separated in-flight using a gas-filled recoil separator and implanted into a position-sensitive silicon detector. Identification of the nuclei was based on position, time, and energy correlations between the implants and subsequent decays.

We investigate quantum corrections to a classical intranuclear cascade simulation of pion single charge exchange on the deuteron. In order to separate various effects, the orders of scattering need to be distinguished and, to that end, we develop signals for each order of scattering corresponding to quasifree conditions. Quantum corrections are evaluated for double scattering and are found to be large. Global agreement with the data is good.

A theoretical study is presented for the disappearance of flow by analyzing a large number of reactions with masses between 47 and 476 units. We demonstrate that the effect of nucleon-nucleon cross sections reduces, to an insignificant level for heavier colliding nuclei in agreement with previous studies. A stiff equation of state with nucleon-nucleon cross sections $\sigma =35–40\text{mb}$ is able to explain all the measured balance energies. A power law $\left(\propto A^{\tau }\right)$ is also given for the mass dependence of disappearance of flow, which is in good agreement with experimental data.

In fragmentation of a finite object such as an atomic nucleus or a percolation lattice, the multidimensional probability distribution of the numbers of fragments of each mass (charge, size) may be approximated as a product of Poisson distributions. In this work we present an analytical treatment of the influence of constraints (multiplicity, mass, etc.) that may be imposed on the basic product distribution.

The vacuum polarization effects from the nucleon sector lead to large medium modifications of the vector meson masses in the Walecka model. With a quantum hadrodynamic framework including the quantum effects, and using a quasiparticle description for quark gluon plasma, the dilepton emission rate from the hot and dense matter resulting from relativistic nuclear collisions is calculated. Using a model for the fireball evolution which has been shown to reproduce other observables such as charmonium suppression, photon emission, and the abundance of hadronic species, we compare with the dilepton invariant mass spectrum measured by the CERES Collaboration at CERN SPS. We also compare the results to a previous calculation where the spectral function of a virtual photon (a key ingredient for the emission rate) has been calculated in a chiral SU(3) model.

Charge balance functions, which identify balancing particle-antiparticle pairs on a statistical basis, have been shown to be sensitive to whether hadronization is delayed by several $\mathrm{fm}∕c$ in relativistic heavy ion collisions. Results from two classes of models are presented here, microscopic hadronic models and thermal models. The microscopic models give results which are contrary to recently published ${\pi }^{+}{\pi }^{-}$ balance functions from the STAR Collaboration, whereas the thermal model roughly reproduces the experimental results. This suggests that charge conservation is local at breakup, which is in line with expectations for a delayed hadronization. Predictions are also presented for balance functions binned as a function of $Q_{\mathrm{inv}}$.

We investigate hadron production as well as transverse hadron spectra from proton-proton, proton-nucleus, and nucleus-nucleus collisions from $2\mathit{A}\mathrm{GeV}$ to $21.3\mathit{A}\mathrm{TeV}$ within two independent transport approaches, i.e., hadron-string dynamics (HSD) and ultrarelativistic quantum molecular dynamics (UrQMD) that are based on quark, diquark, string, and hadronic degrees of freedom. The comparison to experimental data on transverse mass spectra from $pp$, $pA$, and $\mathrm{C}+\mathrm{C}$ (or $\mathrm{Si}+\mathrm{Si}$) reactions shows the reliability of the transport models for light systems. For central $\mathrm{Au}+\mathrm{Au}\left(\mathrm{Pb}+\mathrm{Pb}\right)$ collisions at bombarding energies above $\sim 5\mathit{A}\mathrm{GeV}$, furthermore, the measured $K^{\pm }$ transverse mass spectra have a larger inverse slope parameter than expected from the default calculations. We investigate various scenarios to explore their potential effects on the $K^{\pm }$ spectra. In particular the initial state Cronin effect is found to play a substantial role at top Super Proton Synchrotron (SPS) and Relativistic Heavy Ion Collider (RHIC) energies. However, the maximum in the $K^{+}∕{\pi }^{+}$ ratio at $20–30\mathit{A}\mathrm{GeV}$ is missed by $40\%$ and the approximately constant slope of the $K^{\pm }$ spectra at SPS energies is not reproduced either. Our systematic analysis suggests that the additional pressure—as expected from lattice QCD calculations at finite quark chemical potential ${\mu }_q$ and temperature $T$—should be generated by strong interactions in the early $\text{prehadronic}∕\text{partonic}$ phase of central $\mathrm{Au}+\mathrm{Au}\left(\mathrm{Pb}+\mathrm{Pb}\right)$ collisions.

We present a simple interpretation of the recently observed near-threshold proton-antiproton enhancement. It is described by a set of low-energy parameters deduced from the analysis of $N\overline{N}$ experiments at the Low Energy Antiproton Ring. We predict a related effect in photoproduction reaction under study by CLAS Collaboration.