We examine the validity of the pn quasiparticle RPA (pnQRPA) as a model for calculating ${\mathrm{\beta }}^{+}$ and 2νββ Gamow-Teller decays by making a comparison of the pnQRPA with a large-basis shell-model calculation within the 0f1p shell. We employ A=46 nuclei (those with six valence nucleons) for this comparison. Our comparison includes the decay matrix elements summed over final states, the strength distributions, and, for the first time, the coherent transition matrix elements (CTME). The pnQRPA overestimates the total ${\mathrm{\beta }}^{+}$ and 2νββ matrix elements. There are large differences in the shape of the spectra as well as in the CTME between the pnQRPA and shell-model results. Empirical improvements for the pnQRPA are discussed.

The momentum distribution of fragments produced in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reaction at 28.7 MeV/nucleon is analyzed with an antisymmetrized version of molecular dynamics. Calculations are made for several cases of stochastic collisions and the projectile-fragmentation peak in the momentum distribution is reproduced by the incorporation of the many-body nature into the stochastic collision process. Furthermore, the value of the cross section is found to be reflected in the low-momentum part of fragments such as α particles and ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$.

A relativistic extension of the particle-hole-hole ring-diagram many-body formalism is developed by using the Dirac equation for single-particle motion in the medium. Applying this new formalism, calculations are performed for nuclear matter. The results show that the saturation density is improved and the equation of state becomes softer as compared to corresponding Dirac-Brueckner-Hartree-Fock calculations. Using the Bonn A potential, nuclear matter is predicted to saturate at an energy per nucleon of -15.30 MeV and a density equivalent to a Fermi momentum of 1.38 ${\mathrm{fm}}^{\mathrm{-}1}$, in excellent agreement with empirical information. The compression modulus is 152 MeV at the saturation point.

The one-level R-matrix approach is used to calculate alpha decay widths for several low-lying $0^{+}$, $2^{+}$, and $4^{+}$ excited states of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nucleus. The interior wave functions are calculated within the ZBM (${\mathit{p}}_{1/2}$,${\mathit{d}}_{5/2}$,${\mathit{s}}_{1/2}$) shell-model space with various effective interactions. The exterior wave functions are calculated from an α${+}^{12}$C folding model potential obtained with the M3Y interaction. A new method for calculating the channel radius using the matching of the interior and exterior wave functions in the α-decay channel is presented.

A bound system of ${\mathrm{\pi }}^{\mathrm{-}}$ and neutrons (pineuts) was searched for in the fragmentation region of ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ + Be collisions at 100A MeV. The upper limits for the production cross sections were obtained to be 0.08 and 0.20 nb at the 90% confidence level for singly charged systems ${\mathrm{\pi }}^{\mathrm{-}}$${\mathit{n}}^2$ and ${\mathrm{\pi }}^{\mathrm{-}}$${\mathit{n}}^3$, respectively.

Elastic scattering of protons from ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ in the energy range ${\mathit{E}}_{\mathit{p}}$=9.8 to 135 MeV is analyzed using a dispersive optical model potential (OMP). In this analysis, a dispersion relation connects the volume integrals of the imaginary and the real parts of the OMP. Best-fit dispersive OMP parameters are obtained from fits to experimental cross section and analyzing power data at each energy, while the volume integrals of the imaginary potential and dispersive correction terms are fixed at the empirical values obtained in the individual proton elastic scattering analyses from 9.8 to 135 MeV. Predictions of the cross section and analyzing power angular distributions from the best-fit dispersive OMP and conventional OMP are obtained, and give similar quality fits to data. A dispersive OMP with parameters that show a smooth energy dependence are determined from fits to the entire data set. Comparison of cross sections and analyzing powers calculated by the dispersive OMP with experimental data at 160 and 185 MeV is also presented. The dispersive OMP with a smooth energy dependence is extended to the negative energy region with the guidance of the known first single-particle and single-hole state energies near the Fermi energy, ${\mathit{E}}_{\mathit{F}}$=-6.8 MeV, to provide parameters for the shell model potential. This analysis also provides estimates for single-particle and hole energies ${\mathit{E}}_{\mathit{n}\mathit{l}\mathit{j}}$, root-mean-square radii ${\mathit{R}}_{\mathit{n}\mathit{l}\mathit{j}}$, expectat ion values of the effective mass 〈${\mathit{m}}^{\mathrm{*}}$/m${\mathrm{〉}}_{\mathit{n}\mathit{l}\mathit{j}}$, occupation probabilities ${\mathit{N}}_{\mathit{n}\mathit{l}\mathit{j}}$, absolute spectroscopic factors ${\mathit{S}}_{\mathit{n}\mathit{l}\mathit{j}}$, and spectral functions ${\mathrm{\zeta }}_{\mathit{n}\mathit{l}\mathit{j}}$(${\mathit{E}}_{\mathit{x}}$) for proton single-particle and single-hole orbits in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$. These estimates are compared with available experimental information.

Wave functions of the α particle corresponding to different S- and D-state deuteron-deuteron overlaps, 〈dd‖α〉, were investigated using exact finite-range distorted-wave Born-approximation (DWBA) analyses of (d→,α) reactions. Cross sections, vector, and tensor-analyzing powers were measured for (d→,α) reactions populating the lowest ${\mathit{J}}^{\mathrm{\pi }}$=$7^{+}$ state in ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ at bombarding energies ${\mathit{E}}_{\mathit{d}}$ of 16 and 22 MeV, the lowest $7^{+}$ state in ${}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ at ${\mathit{E}}_{\mathit{d}}$=16 MeV, and the lowest $7^{+}$ state in ${}_{}{}^{46}{}_{}{}^{}\mathrm{Sc}$ at ${\mathit{E}}_{\mathit{d}}$=22 MeV. We find that DWBA analyses of tensor-analyzing powers produce satisfactory agreement with the data and that ${\mathit{A}}_{\mathit{x}\mathit{x}}$ is especially sensitive to the D-state component of α-particle wave functions generated by different realistic nucleon-nucleon interactions.

The interplay between the elastic, quasielastic, and fusion reaction channels at energies from just above to well below the Coulomb barrier is investigated for O+C systems. Elastic-scattering and quasielastic-scattering angular distributions were measured using the kinematic coincidence technique. Fusion yields were obtained by direct detection of the evaporation residues using a time-of-flight energy spectrometer, at energies from just above to well below the Coulomb barrier. The fusion yields differ significantly from previous work, but the present measurements give barrier parameters consistent with systematics. Comparisons with two-center shell model and coupled-channels predictions show possible indications of nuclear-molecular formation in the elastic, inelastic, and single-neutron transfer channels.

Collisions between ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ projectile and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ target nuclei at E/A=35 MeV have been studied with the Michigan State University Miniball, a 4π phoswich array with a low detection threshold. Azimuthal distributions of charged particles with respect to the reaction plane are determined via the transverse-momentum-tensor method. Dependence on the kinetic energy of the emitted particles, the collision geometry, and the associated charged particle multiplicity is investigated. Corrections for the intrinsic resolution of the experimental reaction plane determination are applied. Scaling implied by the coalescence model is explored and the data are compared to the results of microscopic calculations within the Boltzmann-Uehling-Uhlenbeck theory.

${}_{}{}^{58}{}_{}{}^{}\mathrm{induced}$ one- and two-neutron transfer reactions have been measured on ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ at ${\mathit{E}}_{\mathrm{lab}}$=500 MeV. The transfer probabilities at large internuclear distances measured for the deformed ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ target are compared with similar data on spherical ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. For one-neutron transfer reactions good agreement between experiment and the prediction from the tunneling model is observed in both cases. The transfer probabilities for two-neutron transfer reactions deviate from the semiclassical predictions. The disagreement increases at higher bombarding energies. These deviations can be explained by the influence of diffractive effects which become more important at higher bombarding energies.

We have determined the γ-ray branching ratio ${\mathrm{\Gamma }}_{\gamma }$/${\mathrm{\Gamma }}_{\mathrm{tot}}$ for the first excited state in ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}$ (${\mathit{E}}_{\mathit{x}}$=5.17 MeV) to be (3.1±1.7)×${10}^{\mathrm{-}4}$, corresponding to a γ width of 12±7 eV. This value was determined by measuring the ratio of the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$(p,n${)}^{14}$${\mathrm{O}}_0$ to ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$(p,n${)}^{14}$${\mathrm{O}}_1$ cross sections via neutron time of flight, and the ratio of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$(p,n${)}^{14}$${\mathrm{O}}_0$ to ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$(p,n${)}^{14}$${\mathrm{O}}_1$(γ${)}^{14}$${\mathrm{O}}_0$ cross sections at the same center-of-mass energy by bombarding a hydrogen target with a ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ beam and kinematically distinguishing the ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}_0^{}{}_{}{}^{}$ recoils from the two reaction channels. The present value for ${\mathrm{\Gamma }}_{\gamma }$ is consistent with other measurements at the 2-σ level; a weighted mean of all measurements is used to calculate the stellar ${}_{}{}^{13}{}_{}{}^{}\mathrm{N}$(p,γ${)}^{14}$O reaction rate, and thereby determine the temperatures and densities at which the stellar carbon-nitrogen-oxygen (CNO) cycle is converted to the hot CNO cycle.

Differential cross sections were measured and compared to distorted-wave impulse-approximation calculations for the ${\mathit{J}}^{\mathrm{\pi }}$=$4^{\mathrm{-}}$(ν${\mathit{d}}_{5/2}$,π${\mathit{p}}_{3/2}^{\mathrm{-}1}$) state excited in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(n,p${)}^{12}$B (4.52 MeV) reaction, the ${\mathit{J}}^{\mathrm{\pi }}$=$6^{\mathrm{-}}$(ν,${\mathit{f}}_{7/2}$π${\mathit{d}}_{5/2}^{\mathrm{-}1}$) state excited in the ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$(n,p${)}^{28}$Al (5.175 MeV) reaction, and the ${\mathit{J}}^{\mathrm{\pi }}$=${10}^{\mathrm{-}}$(ν${\mathit{h}}_{11/2}$,π${\mathit{g}}_{9/2}^{\mathrm{-}1}$) state excited in the ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$(n,p${)}^{120}$In (≃0.0 MeV) reaction at 300 MeV. We obtained a normalization factor of 0.68 for the ${\mathit{J}}^{\mathrm{\pi }}$=${10}^{\mathrm{-}}$(ν${\mathit{h}}_{11/2}$,π${\mathit{g}}_{9/2}^{\mathrm{-}1}$) state excited in ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$(n,p${)}^{120}$In (≃0.0 MeV) reaction; this is the first ‘‘1ħω’’ stretched state known in this mass region.

We present the results of an energy-dependent and set of energy-independent partial-wave analyses of pion-photoproduction data. The analyses extend from threshold to 1.8 GeV in the laboratory photon energy. Resonance photodecay amplitudes are extracted for the 16 baryon resonances found within this energy range. Comparisons are made with previous determinations and quark model predictions. For the stronger resonances, we find results in good agreement with the earlier determinations of Crawford and Morton.

The results of intranuclear cascade calculations (ideal gas with two-body collisions and no mean field), complemented by a simple percolation procedure, are compared with experimental data on protons and light nuclear fragments (d, t, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$) measured in 400 and 800 MeV/nucleon Ne+Nb collisions using a large solid angle detector. The model reproduces quite well global experimental observables like nuclear fragment multiplicity distributions or production cross sections, and nuclear fragment to proton ratios. For rapidity distributions the best agreement occurs for peripheral reactions. Transverse momentum analysis confirms once again that the cascade, although being a microscopic approach, gives too small a collective flow, the best agreement being reached for Z=2 nuclear fragments. Nevertheless these comparisons are encouraging for further improvements of the model. Moreover, such an approach is easy to extend to any other models that could calculate the nucleon phase space distribution after the compression stage of the reaction, when light nuclear fragments emitted at large angles are constructed from percolation.

Viscous hydrodynamic calculations of high energy heavy-ion collisions (Nb-Nb and Au-Au) from 200 to 800 MeV/nucleon are presented. The resulting baryon rapidity distributions, the in-plane transverse momentum transfer (bounce-off), and the azimuthal dependence of the midrapidity particles (off-plane squeeze out) compare well with Plastic Ball data. We find that the considered observables are sensitive both to the nuclear equation of state and to the nuclear shear viscosity η. Transverse momentum distributions indicate a high shear viscosity (η≊60 MeV/${\mathrm{fm}}^2$ c) in the compression zone, in agreement with nuclear matter estimates. The bulk viscosity ζ influences only the entropy production during the expansion stage; collective observables like flow and dN/dY do not depend strongly on ζ. The recently observed off-plane (φ=90°) squeeze-out, which is found in the triple-differential rapidity distribution, exhibits the strongest sensitivity to the nuclear equation of state. It is demonstrated that for very central collisions, b=1 fm, the squeeze-out is visible even in the double-differential cross section. This is experimentally accessible by studying azimuthally symmetric events, as confirmed recently by data of the European 4π detector collaboration at Gesellchaft für Schwerionforschung Darmstadt.

Formal solutions to the Δ-hole and particle-hole coefficients describing nuclear coherent states are presented using the degenerate schematic model. These solutions are used to analytically solve for the momentum-dependent nuclear form factors in which the target is excited to a transition-spin-isospin, Δ-giant resonance through the creation of coherent Δ-hole states, whereas the projectile is excited to an ordinary spin-isospin giant resonance. The target then decays to its ground state emitting a pion. A more general model operator is proposed that leads to complete coherence for all momenta. The magnitudes of the nuclear form factors are calculated theoretically and the results coming from the completely coherent model are compared to the low-momentum coherent model. The calculation is then completed by introducing these models into the pion triple-differential cross section and energy distributions are calculated and compared. The importance of how the nuclear structure and coherence affect the magnitudes and shapes of the form factors and the pion-energy distributions is assessed.

The penetrability is computed exactly through two-peaked fission barriers consisting of three smoothly joined parabolic segments by evaluating accurately the Weber’s cylinder functions appearing in the exact formulation of Cramer and Nix. When this is compared with the penetrability obtained in the WKB approximation for an identical potential barrier, it is found that the WKB transmission resonances within the intermediate well exhibit variable amounts of energy shifts from the exact resonances as large as 150 keV for narrow wells, for incident energies between the top and the bottom of the well. To illustrate the overall performance of the WKB method as an approximation to fission penetrability calculations, the ratio of penetrabilities by the WKB and the exact methods is graphically presented for all the allowed incident energies. The influence of curvature of the intermediate well, and of adjacent barriers on energy shifts is examined in detail. It is found that the use of accurate values of Weber’s function yields spontaneous fission half-lives which are about 10% higher than the values reported by Cramer and Nix.

For the quasifree (${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^0$) reaction on a wide range of targets at 500 and 400 MeV, the measured effective numbers of protons are found to be in good agreement with those from a simple semiclassical attenuation model based on the nuclear density and the total cross section for free πN scattering. The A dependence for our experimental results was fitted by a power law (∝${\mathit{A}}^{\mathrm{\alpha }}$), and the exponents α were found to be 0.38±0.03 and 0.40±0.06 for 500 and 400 MeV (${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^0$), respectively.

A density-dependent effective interaction is derived from a complete set of Lorentz-invariant NN amplitudes. Its use in a Schrödinger formalism produces results equivalent to use of the relativistic impulse approximation together with the Dirac equation. The effective interaction is defined for elastic scattering as a matrix element of the Lorentz-invariant nucleon-nucleon interaction, which differs from the free t matrix in that distortions are present in three of the Dirac spinors. A similar reduction of the relativistic distorted-wave impulse approximation for inelastic scattering is performed to obtain an inelastic effective interaction, which differs from the free t matrix in that distortions are present in all four of the Dirac spinors. A local-density approximation is used to evaluate the effective interactions. For elastic scattering, using the elastic effective interaction in the Schrödinger equation leads to a reasonable reproduction of the relativistic impulse approximation results. The effective interaction is similar to a phenomenological effective interaction obtained by fitting experimental data for elastic and inelastic scattering. The inelastic effective interaction can be used in conventional nonrelativistic analyses based on the distorted-wave impulse approximation and it provides a simple method for incorporating relativistic effects. The full spin and isospin dpendence of the inelastic effective interaction is developed.

An inversion scheme is presented to derive the potentials of algebraic scattering theory from the corresponding S functions. Representative heavy ion scattering data of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ions on ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, accurately fitted by McIntyre strong absorption type S functions, are employed to obtain exact algebraic potentials and to generalize the analytical shapes proposed previously by Alhassid et al. The coordinate space potentials corresponding to a number of S functions are also obtained via semiclassical inversion.