We refine the theoretical treatment of two-neutron transfer between deformed nuclei of the rare-earth region and a heavy spherical nucleus in the Pb region. The refinement from our previous work on effects of the Berry phase interference around the backbending region is that we now include the two lowest rotational bands of both the A and A+2 nucleus rather than the lowest. The inclusion of two bands, ground and aligned, was earlier done by Dasso and Winther, who found diabolic interference effects to be small. We make numerical calculations on somewhat more favorable cases for experimental study, and we include nuclear optical potential effects and finite ${\mathit{Q}}_{\mathit{r}\mathit{x}}$ values.

A dielectron signal for pair masses greater than ${\mathit{M}}_{\mathrm{\pi }}$ is observed in Nb+Nb collisions at 1.05 GeV/nucleon beam kinetic energy. The invariant mass spectrum and the associated multiplicity distribution are presented. Comparisons are made with previous cross section measurements in p+Be and Ca+Ca.

In order to evaluate qualitatively and in order of magnitude the result of some collective effects on dense matter, a specific model is studied: the Walecka’s model of nuclear matter. In this model, the meson fields contribute to the various observables in the Hartree approximation only while all correlations give rise to a collision term considered in the relaxation-time approximation. Within these approximations, a transport equation is given and solved in the Chapman-Enskog expansion in first order. The main transport coefficients (thermal conductivity, shear and bulk viscosities) are calculated and compared to the results first obtained by Anderson and Witting.

The emission rates for photons from hadronic matter are calculated for the elementary processes πρ→πγ, ππ→ργ, and ρ→ππγ at T=100, 150, 200 MeV. Hadronic matter is described by an effective chiral Lagrangian with pions, ρ mesons, and ${\mathit{A}}_1$ mesons. The vector and axial-vector mesons are included as massive Yang-Mills fields of chiral U(${\mathit{N}}_{\mathit{f}}$${)}_{\mathit{L}}$×U(${\mathit{N}}_{\mathit{f}}$${)}_{\mathit{R}}$ symmetry. The emission rates are compared with those obtained without the ${\mathit{A}}_1$ meson. For πρ→πγ and ππ→ργ reactions the photon emission rates are increased with the inclusion of the ${\mathit{A}}_1$ meson in intermediate states. There is a small increase of the emission rate from ρ-meson decay.

The well-known QCD effect of color transparency or opacity induces fluctuations in the hadronic cross sections. We have investigated the effect of cross-section fluctuations in the transverse energy production in ultrarelativistic heavy ion collisions in the geometric model. The fluctuating cross sections are characterized by a normal distribution. The variance of the distribution is obtained by explicitly fitting the transverse energy cross-sectional data. Fluctuations, order of magnitude less than found in NN collisions, are obtained.

A correlator of QCD interpolating fields for the nucleon is evaluated in nuclear matter by applying an operator product expansion. All density dependence is incorporated into the composite operator matrix elements (condensates) taken in the nuclear matter ground state. The in-medium condensates up to dimension five are estimated to first order in the nucleon density. The key phenomenological inputs used in determining the quark and gluon condensates up to dimension four are the nucleon σ term, the strangeness content of the nucleon, and quark and gluon distribution functions deduced from deep-inelastic scattering experiments. Dimension-five quark and quark-gluon condensates, which give small contributions to the correlator, are estimated by a variety of techniques. Contributions from dimension-six four-quark condensates are also included in a factorized form.

We study the nonrelativistic response of a ‘‘diquark’’ bound by confining forces, for which perturbation theory in the interaction fails. As nonperturbative alternatives we consider the Gersch-Rodriguez-Smith (GRS) theory and a summation method. We show that, contrary to the case of singular repulsive forces, the GRS theory can generally be applied to confined systems. When expressed in the GRS-West kinematic variable y, the response has a standard asymptotic limit and calculable dominant corrections of orders 1/q, 1/${\mathit{q}}^2$. That theory therefore clearly demonstrates how constituents, confined before and after the absorption of the transferred momentum and energy, behave as asymptotically free particles. We compare the GRS results with those of a summation method for harmonic and square-well confinement and also discuss the convergence of the GRS series for the response in powers of 1/q.

We have measured the electron-capture decay branch of ${}_{}{}^{100}{}_{}{}^{}\mathrm{Tc}$ to be (1.8±0.9)×${10}^{\mathrm{-}3}$%, from which we deduce logft=4.${45}_{\mathrm{-}0.30}^{+0.18\mathrm{}}$. This indicates that a two-step process connecting only the ground states of ${}_{}{}^{100}{}_{}{}^{}\mathrm{-}_{}^{100}{}_{}{}^{}$Tc${\mathrm{-}}^{100}$Ru can account for the measured 2ν double-β-decay rate of ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$.

We have measured the internal bremsstrahlung spectrum of the electron capture decay of ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ge}$ in search for a possible mass component of the emitted neutrino. The main relevance of this experiment is given by the collected statistics which is 20 times larger than in a previously published work studying the same decay. Analyses of the data exclude the presence of a massive component of 17.$2_{\mathrm{-}1.1}^{+1.3\mathrm{}}$ keV and (1.6±0.7)% mixing fraction claimed by Zlimen et al. for this same nucleus, at the 99.0% confidence level.

The parity-violating longitudinal asymmetry scrA is calculated for quasielastic electron scattering. We use a varietry of relativistic mean field models for the response of nuclear matter and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at a momentum transfer of q=550 MeV/c. Relativistic effects from a reduced nucleon mass, RPA correlations, and vacuum polarization can all change scrA by a relatively large amount. These large nuclear structure corrections could make it impossible to extract strange quark matrix elements or radiative corrections to weak axial currents.

${}_{}{}^6{}_{}{}^{}\mathrm{He}$ beta decay to α+d continuum is studied in a three-body α+N+N approach. The branching ratio for beta-delayed deuteron emission is found to be (3–4)×${10}^{\mathrm{-}5}$ for three-body ${}_{}{}^6{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ wave functions reproducing the ft value for ${}_{}{}^6{}_{}{}^{}\mathrm{He}$ with great accuracy. The results are sensitive to the neutron halo structure of the ${}_{}{}^6{}_{}{}^{}\mathrm{He}$ nucleus.

Beta-decay half-lives and β-delayed neutron-emission probabilities of the very neutron-rich nuclei ${}_{}{}^{44}{}_{}{}^{}\mathrm{S}$ and ${}_{}{}^{45–47}{}_{}{}^{}\mathrm{Cl}$ have been measured. These isotopes, which lie at or close to the N=28 magic shell, were produced in interactions of a 60 MeV/u ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ beam from GANIL (Grand Accélérateur National d’Ions Lourds) with a ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ target, and were separated by the doubly achromatic spectrometer LISE (Ligne d’Ions Super Epluchés). Their decay was studied by a β-n time correlation measurement. The results are compared to recent model predictions and indicate a rapid weakening of the N=28 shell effect below ${}_{20}{}^{48}{}_{}{}^{}\mathrm{Ca}_{28}^{}{}_{}{}^{}$. The nuclear structure effects reflected in the decay properties of the exotic S and Cl isotopes may be the clue for the astrophysical understanding of the unusual ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$${/}^{46}$Ca abundance ratio measured in the solar system as well as the Ca-Ti-Cr anomalies observed in E. King inclusions of the Allende meteorite.

Uncertainties which limit the use of the ${}_{}{}^{187}{}_{}{}^{}\mathrm{-}_{}^{187}{}_{}{}^{}$Os isobaric pair as a cosmochronometer for the age of the galaxy and the universe include those of the partial half-lives of the continuum and bound-state decays of ${}_{}{}^{187}{}_{}{}^{}\mathrm{Re}$. While the total half-life of the decay is well established, the partial half-life for the continuum decay is uncertain, and several previous measurements are not compatible with each other. A high-temperature quartz proportional counter has been used in this work to remeasure the continuum decay of ${}_{}{}^{187}{}_{}{}^{}\mathrm{Re}$ by introducing a metallo-organic rhenium compound into the counting gas. The measured beta end-point energy for the continuum decay of neutral ${}_{}{}^{187}{}_{}{}^{}\mathrm{Re}$ to singly ionized ${}_{}{}^{187}{}_{}{}^{}\mathrm{Os}$ of 2.70±0.09 keV agrees with earlier results. However, the present half-life measurement of (45±3) Gyr agrees within the quoted uncertainties only with the earlier measurement of Payne [Ph.D. thesis, University of Glasgow, 1965 (unpublished)] and Drever (private communication). The new half-life for the continuum decay and the total half-life of (43.5±1.3) Gyr, as reported by Linder et al. [Nature (London) 320, 246 (1986)] yield a branching ratio for the bound-state decay into discrete atomic states of (3±6)%. This is in agreement with the most recent calculated theoretical branching ratio of approximately 1%.

We study results from the recent measurement of the 0° ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$(n,p${)}^{59}$Fe cross section in order to compute the stellar electron capture rate of ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$. This nucleus is the second most important electron capture nucleus in the core of a type II supernova progenitor just before core collapse. It is also the first nucleus which has a large effect on the stellar neutronization rate for which Gamow-Teller strength has been measured. The Gamow-Teller resonance has been observed experimentally at a higher energy above the daughter ground state than one would expect from independent particle shell model arguments, but large-basis shell model calculations employing configuration mixing are more successful in predicting the location of the strength. Because of the high energy of the Gamow-Teller resonance, the stellar electron capture rate and associated neutronization is much less than previous estimates had indicated. Similar trends are seen for ${}_{}{}^{60}{}_{}{}^{}\mathrm{Co}$, the most important electron capture nucleus for supernova progenitors just before core collapse.

Fusion cross sections for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{144}$Nd at bombarding energies ranging from ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=54.0 to 67.5 MeV were measured by observation of the delayed x rays emitted in the radioactive decay of the evaporation residues and their daughters. The experimental fusion excitation function was analyzed with a barrier penetration model which includes coupling to inelastic channels. The theoretical average angular momenta were calculated and compared with already existing data deduced from γ-multiplicity measurements.

Complete disintegrations of Ag and Br nuclei caused by a 4.5A GeV/c ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ projectile have been analyzed to study the characteristics of the collisions with small impact parameters. The results are systematically compared with their corresponding values obtained for the interactions with comparatively larger impact parameters at the same beam momentum per nucleon. The variations of the mean multiplicity of the relativistic charged particles with the mean number of the interacting nucleons of the projectile nuclei and the normalized pseudorapidity density have also been examined.

The shapes of even-even N=Z nuclei ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ge}$, ${}_{}{}^{68}{}_{}{}^{}\mathrm{Se}$, ${}_{}{}^{72}{}_{}{}^{}\mathrm{Kr}$, ${}_{}{}^{76}{}_{}{}^{}\mathrm{Sr}$, and ${}_{}{}^{80}{}_{}{}^{}\mathrm{Zr}$ are studied using deformed relativistic mean field theory. Large deformations (β≊0.5) for ground states are found for ${}_{}{}^{76}{}_{}{}^{}\mathrm{Sr}$ and ${}_{}{}^{80}{}_{}{}^{}\mathrm{Zr}$ nuclei. The microscopic structures of these superdeformed configurations are emphasized.

The strangeness production process p¯p→Ξ¯Ξ is investigated in a meson exchange model and a full coupled channel treatment. Results for cross sections, polarizations, and singlet fractions are presented and compared with those obtained from quark-gluon models. Characteristic differences occur in the (p¯p→Ξ${\mathrm{¯}}^{\mathrm{-}}$${\mathrm{\Xi }}^{\mathrm{-}}$)/(p¯p→Ξ${\mathrm{¯}}^0$${\mathrm{\Xi }}^0$) cross section ratios.

The single-particle distribution function of moving fused compounds, with velocities of the order of a few tenths of the velocity of light, are calculated using the discrete spectrum of single-particle states of deformed nuclei. The polarization of single-particle momenta in the direction of flight is clearly brought out. Results are presented for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{71}{}_{}{}^{}\mathrm{As}$, and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$. For small temperatures when the internal excitations are small, the nuclear level density varies as E(${\mathit{E}}^2$-${\mathit{M}}^2$${)}^{1/2}$ where E is the total energy of the moving nuclei, and, as excitation increases, the internal degrees of freedom dominate and the level density ρ∼${\mathit{e}}^{\mathit{S}}$, where S is the entropy of the system, varies exponentially. The level densities thus calculated are used to evaluate light charged-particle emission from hot fused compounds in motion.

A density dependent, nucleon-nucleon effective interaction based on the relativistic impulse approximation model of Tjon and Wallace is used in a Schrödinger equation calculation to predict scattering observables for 500 MeV polarized proton elastic scattering from polarized ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$. The calculated observables are compared to experimental data, providing the first, quantitative test of the spin-flip components of the Tjon and Wallace interaction. The theoretical predictions are in qualitative agreement with the data and are similar to those of nonrelativistic multiple-scattering theory.