Resonance particle ratios and spectra are calculated in the sequential binary emission model for hadrons produced from the decay of a single massive resonance formed in relativistic heavy ion collisions. The sequential model which is quite successful in reproducing the yield ratios for stable hadrons at energies currently available at the BNL Relativistic Heavy Ion Collider (RHIC) is found to describe remarkably well the yield ratios for the resonances $K^{*}(892){}^0$ and ϕ mesons. The model indicates a short expansion time between the average chemical and thermal freeze-out with negligible regeneration of the resonances via the inverse two-body elastic collision process. Model estimates of the yield ratios for the strange baryons $\Lambda (1520)$ and $\Sigma (1385)$ are presented.

We investigate the asymptotic separation of the optical model potential for nucleon-nucleus scattering in momentum space, where the potential is split into a medium-independent term and another depending exclusively on the gradient of the density-dependent $g$ matrix. This decomposition confines the medium sensitivity of the nucleon-nucleus coupling to the surface of the nucleus. We examine this feature in the context of proton-nucleus scattering at beam energies between 30 and 100 MeV and find that the $\mathit{pn}$ coupling accounts for most of this sensitivity. Additionally, based on this general structure of the optical potential we are able to treat both, the medium dependence of the effective interaction and the full mixed density as described by single-particle shell models. The calculated scattering observables agree within 10% with those obtained by Arellano, Brieva, and Love in their momentum-space $g$-folding approach.

We examine the effective interaction of nonrelativistic fermions with an external vector field in superfluid systems. In contrast to the complicated vertex equation, usually used in this case, we apply the approach that does not employ an explicit form of the pairing interaction. This allows us to obtain a simple analytic expression for the vertex function only in terms of the order parameter and other macroscopic parameters of the system. We use this effective vertex to analyze the linear response function of the superfluid medium at finite temperatures. At the time-like momentum transfer, the imaginary part of the response function is found to be proportional to $V_F^4$, i.e., the energy losses through vector currents are strongly suppressed. As an application, we calculate the neutrino energy losses through neutral weak currents caused by the pair recombination in the superfluid neutron matter at temperatures lower than the critical one for the ${}^1{S}_0$ pairing. This approach confirms a strong suppression of the neutrino energy losses as predicted in L. B. Leinson and A. Pérez [Phys. Lett. B638, 114 (2006)].

Using the covariant spectator theory (CST), we present two one-boson-exchange kernels that have been successfully adjusted to fit the 2007 world $\mathit{np}$ data (containing 3788 data) below 350 MeV. One model (which we designate WJC-1) has 27 parameters and fits with a ${\chi }^2/N_{\mathrm{data}}=1.06$. The other model (designated WJC-2) has only 15 parameters and fits with a ${\chi }^2/N_{\mathrm{data}}=1.12$. Both of these models also reproduce the experimental triton binding energy without introducing additional irreducible three-nucleon forces. One result of this work is a new phase-shift analysis, updated for all data until 2006, which is useful even if one does not work within the CST. In carrying out these fits we have reviewed the entire database, adding new data not previously used in other high precision fits and restoring some data omitted in previous fits. A full discussion and evaluation of the 2007 database is presented.

Observables in elastic proton-deuteron scattering are sensitive probes of the nucleon-nucleon interaction and three-nucleon force effects. The present experimental database for this reaction is large, but contains a large discrepancy between data sets for the differential cross section taken at 135 MeV/nucleon by two experimental research groups. This article reviews the background of this problem and presents new data taken at Kernfysisch Versneller Instituute (KVI). Differential cross sections and analyzing powers for the ${}^2\mathrm{H}(\overrightarrow{p},d)p$ and ${}^1\mathrm{H}(\overrightarrow{d},d)p$ reactions at 135 MeV/nucleon and 65 MeV/nucleon, respectively, have been measured. The differential cross-section data differ significantly from previous measurements and consistently follow the energy dependence as expected from an interpolation of published data taken over a large range at intermediate energies.

The ${}^{12}\mathrm{C}$(${}^{16}\mathrm{O}$,${}^{14}\mathrm{O}$)${}^{14}\mathrm{C}$ reaction was studied at a beam energy of 234 MeV. The ${}^{14}\mathrm{O}$ ejectile was detected by a Q3D spectrometer at forward angles. The energies and angles of the excited ${}^{14}\mathrm{C}$ recoil break-up fragments were measured in coincidence with the ${}^{14}\mathrm{O}$ ejectile using a double sided silicon strip detector array at backward angles. A complete kinematic reconstruction of the reaction was performed to reconstruct the ${}^{14}{\mathrm{C}}^{*}\to {}^{10}\mathrm{Be}+\alpha$ and ${}^{14}{\mathrm{C}}^{*}\to {}^{13}\mathrm{C}+n$ decay channels and the branching ratios and widths of these decays were calculated. Theoretical decay branches were calculated using barrier penetrability factors and were compared to the measured ratios to provide information on the spins, parities, and configurations of the states. Neutron emission was found to be favored for the 11.73, 12.96, 14.87, 16.72, and 18.6 MeV states. The 14.87, 18.6, and 21.4 MeV states were found to have a considerable width for $\alpha$-decay and are candidates for the three bodied molecular cluster structure of ${}^{14}\mathrm{C}$.

Excited states in ${}^{192}\mathrm{Pt}$ were populated in ${\beta }^{+}/\epsilon$ decay and studied through off-beam $\gamma$-ray spectroscopy. New coincidence data give no support for several reported low-energy, low-spin states proposed in $\beta$ decay and lead to a substantially revised level scheme. The structure of ${}^{192}\mathrm{Pt}$ is discussed in terms of both single-space IBA-1 calculations and two-space IBA calculations with configuration mixing. Both models together suggest that it is the perhaps the $0_4^{+}$ state that corresponds to an intruder excitation, resulting from the excitation of a pair of protons across the $Z=82$ closed shell.

The experimental information on isospin-spin excitations around ${}^{58}\mathrm{Ni}$ is analyzed by using isoscalar and isovector pairing vibrations, Gamow-Teller (GT) modes, and their couplings. It is found that the proposed coupling scheme accounts for a sizable amount of the strength associated with isospin-spin excitations, which include transitions to both one- and two-phonon states. The calculations are performed within the framework of perturbation theory, accounting for the renormalization of the charge by the collective GT excitations.

Broyden's method, widely used in quantum chemistry electronic-structure calculations for the numerical solution of nonlinear equations in many variables, is applied in the context of the nuclear many-body problem. Examples include the unitary gas problem, the nuclear density functional theory with Skyrme functionals, and the nuclear coupled-cluster theory. The stability of the method, its ease of use, and its rapid convergence rates make Broyden's method a tool of choice for large-scale nuclear structure calculations.

The elastic and large-angle quasi-elastic scattering reactions were studied with the same nucleus-nucleus potential proposed for describing fusion reactions. The elastic scattering angle distributions of some reactions are reasonably well reproduced by the proposed Woods-Saxon potential with fixed parameters at energies much higher than the Coulomb barrier. With an empirical barrier distribution based on the modified Woods-Saxon potential and taking into account the influence of nucleon transfer, the calculated quasi-elastic scattering cross sections of a series of reactions are in good agreement with the experimental data.

Charge asymmetry in electron (positron) scattering arises from the interference of the Born amplitude and the box-type amplitude corresponding to two virtual photons exchange. It can be extracted from electron-proton and positron-proton scattering experiments, in the same kinematical conditions. Considering the virtual photon Compton scattering tensor, which contributes to the box-type amplitude, we separate proton and inelastic contributions in the intermediate state and parametrize the proton form factors as the sum of long-distance and short-distance interaction terms. Arguments based on analyticity are given in favor of cancellation of contributions from proton strong-interaction form factors and of inelastic intermediate states in the box-type amplitudes. In the framework of this model, with a realistic expression for nucleon form factors, numerical estimations are given for moderately high energies.

New results on the rare, doubly radiative decay $\eta \to {\pi }^0\gamma \gamma$ have been obtained from a revised analysis of the Crystal Ball experiment performed at the AGS. The analysis yields the first information on the dependence of the decay width, $\Gamma (\eta \to {\pi }^0\gamma \gamma )$, on the two-photon invariant mass squared, $m^2(\gamma \gamma )$. A re-evaluation of the branching ratio is also made, $\mathit{BR}(\eta \to {\pi }^0\gamma \gamma )=(2.21\pm 0.{24}_{\mathrm{stat}}\pm 0.{47}_{\mathrm{syst}})\times {10}^{-4}$; it implies that the decay width is $\Gamma (\eta \to {\pi }^0\gamma \gamma )=0.285\pm 0.{031}_{\mathrm{stat}}\pm 0.{061}_{\mathrm{syst}}$ eV. These results are close to predictions based on chiral perturbation theory with vector-meson dominance.

We study the composition of the outer layers of a protoneutron star and show that light nuclei are present in substantial amounts. The composition is dominated by nucleons, deuterons, tritons and alpha particles; ${}^3\mathrm{He}$ is present in smaller amounts. This composition can be studied in laboratory experiments with new neutron-rich radioactive beams that can reproduce similar densities and temperatures. After including the corresponding neutrino interactions, we demonstrate that light nuclei have a small impact on the average energy of the emitted electron neutrinos, but are significant for the average energy of antineutrinos. During the early post-explosion phase, the average energy of electron antineutrinos is slightly increased, while at later times during the protoneutron star cooling it is reduced by about 1 MeV. The consequences of these changes for nucleosynthesis in neutrino-driven supernova outflows are discussed.

The problem of the effective mass scaling in the single-particle (s.p.) spectra calculated within the Skyrme energy density functional (EDF) method is studied. It is demonstrated that for specific pairs of orbitals like $1d_{3/2}\text{−}1f_{7/2}$ the commonly anticipated isoscalar effective mass ($m^{*}$) scaling of the s.p. level splittings is almost canceled by an implicit $m^{*}$ scaling present in the two-body spin-orbit (SO) strength. On the other hand, the $\nu f_{7/2}\text{−}\nu f_{5/2}$ SO splitting depends solely on the SO strength. Hence, two conflicting scaling properties appear to be at work in standard Skyrme EDF, making the theory internally inconsistent with respect to s.p. energies. It is argued that this unphysical property is, to a large extent, a consequence of the strategies and data sets used to fit these functionals. The inclusion of certain s.p. spin-orbit splittings to fit the two-body spin-orbit and the tensor interaction strengths reinstates the conventional $m^{*}$ scaling and improves the performance of the Skyrme EDF.

The ${}^{24}\mathrm{Mg}({}^3\mathrm{He},t){}^{24}$Al reaction was studied at $E({}^3\mathrm{He})=420$ MeV. An energy resolution of 35 keV was achieved. Gamow-Teller strengths to discrete levels in ${}^{24}\mathrm{Al}$ were extracted by using a recently developed empirical relationship for the proportionality between Gamow-Teller strengths and differential cross sections at zero momentum transfer. Except for small discrepancies for a few weak excitations, good agreement with previous ${}^{24}\mathrm{Mg}$($p,n$) data and nuclear-structure calculations using the USDA/B interactions in the $\mathit{sd}$ shell-model space was found. The excitation energy of several levels in ${}^{24}\mathrm{Al}$ of significance for determination of the ${}^{23}\mathrm{Mg}$${(p,\gamma )}^{24}$Al thermonuclear reaction rate were measured. Results are consistent with two of the three previous (${}^3\mathrm{He}$,$t$) measurements, performed at much lower beam energies. However, a new state at $E_x({}^{24}\mathrm{Al})=2.605(10)$ MeV was found and is the third state above the proton separation energy.

The systematic investigation of hyperdeformation (HD) at high spin in the $Z=40-58$ region of the nuclear chart was performed in the framework of the cranked relativistic mean-field theory. The properties of the moments of inertia of the HD bands, the role of the single-particle and necking degrees of freedom at HD, the spins at which the HD bands become yrast, the possibility to observe discrete HD bands, and so on are discussed in detail.

The angular momentum decomposition of pairs obtained using Richardson's exact solution of the pairing Hamiltonian for the deformed ${}^{174}\mathrm{Yb}$ nucleus are displayed. The probabilities for low angular momenta of the collective pairs are strikingly different from the ones obtained in the BCS ground state.

Two microscopic models, ultrarelativistic quantum molecular dynamics and quark-gluon string model, were employed to study the formation of locally equilibrated hot and dense nuclear matter in heavy-ion collisions at energies from $11.6A$ to $160A$ GeV. Analysis was performed for the fixed central cubic cell of volume $V=125$ fm${}^3$ and for the expanding cell that followed the growth of the central area with uniformly distributed energy. To decide whether the equilibrium was reached, results of the microscopic calculations were compared to that of the statistical thermal model. Both dynamical models indicate that the state of kinetic, thermal and chemical equilibrium is nearly approached at any bombarding energy after a certain relaxation period. The higher the energy, the shorter the relaxation time. Equation of state has a simple linear dependence $P=a(\sqrt{s})\varepsilon$, where $a\equiv c_s^2$ is the sound velocity squared. It varies from $0.12\pm 0.01$ at $E_{\mathrm{lab}}=11.6A$ GeV to $0.145\pm 0.005$ at $E_{\mathrm{lab}}=160A$ GeV. Change of the slope in $a(\sqrt{s})$ behavior occurs at $E_{\mathrm{lab}}=40A$ GeV and can be assigned to the transition from baryon-rich to meson-dominated matter. The phase diagrams in the $T\text{−}{\mu }_{\mathrm{B}}$ plane show the presence of kinks along the lines of constant entropy per baryon. These kinks are linked to the inelastic (i.e., chemical) freeze-out in the system.

In the late stage of the evolution of a pion system in high-energy heavy-ion collisions when pions undergo multiple scatterings, the quantum transport of the interfering pair of identical pions plays an important role in determining the characteristics of the Hanbury-Brown–Twiss (HBT) interference. We study the quantum transport of the interfering pair using the path-integral method, in which the evolution of the bulk matter is described by relativistic hydrodynamics while the paths of the two interfering pions by test particles following the fluid positions and velocity fields. We investigate in addition the effects of secondary pion sources from particle decays, for nuclear collisions at AGS and RHIC energies. We find that quantum transport of the interfering pair leads to HBT radii close to those for the chemical freeze-out configuration. Particle decays however lead to HBT radii greater than those for the chemical freeze-out configuration. As a consequence, the combined effects give rise to HBT radii between those extracted from the chemical freeze-out configuration and the thermal freeze-out configuration. Proper quantum treatments of the interfering pairs in HBT calculations at the pion multiple scattering stage are important for our understanding of the characteristics of HBT interferometry in heavy-ion collisions.

We have redetermined the $g$ factor and the lifetime of the $2_1^{+}$ state in ${}^{40}\mathrm{Ar}$ by applying the technique of α transfer from a carbon target to ${}^{36}\mathrm{S}$ beams in inverse kinematics combined with transient magnetic fields. In addition, the lifetimes of the $4_1^{+}$ and the $2_2^{+}$ states in ${}^{40}\mathrm{Ar}$ have been remeasured using the Doppler-shift-attenuation method (DSAM). Additional experimental details of the α-transfer measurements are provided. The results are discussed within the framework of new large-scale shell model calculations with both free and effective nucleon $g$ factors.