Techniques are developed in order to study static magnetic screening and other nonperturbative aspects of QCD at high temperatures. In particular, a covariant derivative expansion of the one-loop effective action is presented and then modified by an infinite resummation so as to provide agreement with the exactly calculable one-loop effective potential. Essential to this technique is a self-consistently defined infrared cutoff which determines the prefactor in semiclassical calculations. Using this prefactor, densities of monopole and dyon plasmas are calculated, and it is found that if such plasmas do exist at finite temperature, then the solitons involved must be overlapping one another. It is also shown that no consistent perturbative or nonperturbative approximation can give rise to a linear term in the SU(2) effective potential, since such a term would not be gauge invariant. Finally, contour plots of the SU(3) ${\mathit{A}}_0$ effective potential are presented.

We apply the BRST quantization method to the treatment of collective coordinates in a simplified baryon model displaying a breakdown of symmetries. The formalism allows us, in particular, to perform perturbative calculations which are free from infrared divergencies. We obtain the corrections to the ground state energy and to the expectation value of the transition operator.

Pionic contributions to static nucleon properties are calculated in a chiral extension of the color-dielectric model. The pion field and residual gluon field are treated perturbatively. It is shown that with a simple choice for the energy of the scalar confining field and assuming the chiral limit, the system of equations describing the bare soliton and the perturbative pion and gluon fields may be cast in a dimensionless, parameter-free form for large glueball masses. This enables a formula for the masses of the nucleon and Δ including leading-order pionic and gluonic contributions and corrections for spurious center-of-mass motion, valid for a wide range of input parameters determining the bare-soliton solutions, to be derived. A further consequence of the scaling behavior is that pionic contributions to nucleon properties, calculated using the methods of the cloudy-bag model, are insensitive to the soliton parameters, once the size of the soliton is fixed. The model results are very similar to those of the cloudy-bag model but the predicted masses are about 20% too large, and the pionic contributions to charge radii are underestimated.

Mass separated sources of ${}_{}{}^{223}{}_{}{}^{}\mathrm{Ac}$ with ${}_{}{}^{219}{}_{}{}^{}\mathrm{Fr}$ in secular equilibrium were used to study the level structure of ${}_{}{}^{215}{}_{}{}^{}\mathrm{At}$ following alpha decay of ${}_{}{}^{219}{}_{}{}^{}\mathrm{Fr}$. The levels in ${}_{}{}^{215}{}_{}{}^{}\mathrm{At}$ can be interpreted in terms of the π(${\mathit{h}}_{9/2}$${)}^3$ν(${\mathit{g}}_{9/2}$${)}^4$, π(${\mathit{h}}_{9/2}$${)}^2$${\mathit{f}}_{7/2}$ν(${\mathit{g}}_{9/2}$${)}^4$, and π(${\mathit{h}}_{9/2}$${)}^2$${\mathit{i}}_{13/2}$ν(${\mathit{g}}_{9/2}$${)}^4$ shell model configurations. No evidence for reflection asymmetry is found.

With the use of an on-line mass separator, electron capture (EC) and ${\mathrm{\beta }}^{+}$ decay of the direct proton emitter ${}_{}{}^{147}{}_{}{}^{}\mathrm{Tm}$ was identified in a series of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${+}^{92}$Mo irradiations. Characteristic Er Kα x rays and an 80.9-keV γ ray were observed to decay with the half-life of ${}_{}{}^{147}{}_{}{}^{}\mathrm{Tm}$. The 80.9-keV γ ray is proposed to be the transition connecting the first-excited (${\mathit{d}}_{3/2}$) and ground (${\mathit{s}}_{1/2}$) neutron-hole states in ${}_{}{}^{147}{}_{}{}^{}\mathrm{Er}$. The ${}_{}{}^{147}{}_{}{}^{}\mathrm{Tm}$ (EC+${\mathrm{\beta }}^{+}$)-decay strength was deduced from K x-ray and annihilation radiation intensities. A comparison of this strength with the intensity of the 1.045-MeV proton peak leads to a ${}_{}{}^{147}{}_{}{}^{}\mathrm{Tm}$ direct-proton-decay branch of 15(5)%.

In a nonrelativistic quark model, we develop a very simple formalism to show that the Pauli principle at the quark level implies certain symmetry requirements for a system of two nonidentical hadrons. Observable features at the level of the hadron-hadron interaction are pointed out for some particular systems.

A theoretical approach to describing the electromagnetic interaction in hadronic field theories containing charged mesons at finite baryon density is presented. Path-integral methods and bilocal auxiliary fields are used to identify covariant, gauge-invariant levels of approximation, which sum infinite classes of Feynman diagrams. At the lowest level an isolated nucleon acquires a nontrivial electromagnetic structure, and the finite-density nucleus is described as a noninteracting system of quasiparticles with that structure.

We point out that the data used in the sdg boson model calculations by Devi and Kota [Phys. Rev. C 45, 2238 (1992)] can be equally well described by the much simpler sd boson model. We present additional data for the Sm isotopes which cannot be explained in the sd model and hence may justify such an extension to the sdg bosons. We also comment on the form of the Hamiltonian and the transition operators used in this paper.

Evidence for collective oblate behavior in ${}_{}{}^{196}{}_{}{}^{}\mathrm{Pb}$ is presented. One irregular and two regular bands of M1 transitions have been observed following the ${}_{}{}^{170}{}_{}{}^{}\mathrm{Er}$${(}^{30}$Si,4n) and ${}_{}{}^{176}{}_{}{}^{}\mathrm{Yb}$${(}^{26}$Mg,6n) reactions. Transitions linking the most intense regular band to the low-lying negative-parity yrast levels are observed, establishing excitation energies, spins, and probable parities of the band members. In contrast, no such transitions have been found for the irregular band and the weaker regular band. The bands are interpreted as corresponding to collective oblate rotation, arising mainly from deformation-aligned high-j, shape-driving quasiproton excitations across the Z=82 shell gap, coupled to rotation-aligned quasineutrons.

One- and two-proton stripping cross sections were measured for ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$${+}^{92,98,100}$Mo and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$ systems at laboratory energies of 125, 116, and 109 MeV. The angular distributions were compared with distorted wave Born approximation calculations where reasonable agreements were shown for one-proton stripping. The two-proton transfer probability shows an anomalous dependence on distance of closest approach at energies above the Coulomb barrier for all targets. This slope anomaly disappears at energies below the barrier. A simple model suggests that the one-proton transfer mechanism at these energies is dominated by semiclassical dynamics, while for two-proton transfer at energies above the barrier a diffraction process is dominant due to localization in angular momentum space.

Low-lying hexadecapole states in stable even-even neodymium isotopes have been investigated by means of inelastic electron scattering. Transition charge densities were extracted in a Fourier-Bessel analysis of the form factors. The analysis of the experimental results within the interacting sdg-boson model with only one g boson allowed the extraction of the radial shapes of the hexadecapole structure functions of three of the different boson-pair configurations (i.e., dd, sg, and dg) involved in the hexadecapole excitations.

Antiproton production cross sections have been measured in minimum bias p+Be, p+Al, p+Cu, and p+Au collisions at 14.6 GeV/c with the E-802 spectrometer at the Brookhaven Alternating Gradient Synchrotron. The antiproton multiplicity at laboratory rapidities 1.0 to 1.6 shows almost no dependence upon the target mass. The p¯ production for p+Be is somewhat lower than an estimation based upon 19–24 GeV/c p+p data. In this rapidity interval the antiproton yield scales by a factor of 28±6 from p+Au to central Si+Au collisions.

Antiproton production from heavy ion collisions involves a strong competition between creation and annihilation mechanisms. Due to the high threshold energy, antiprotons mostly arise from the highest energy baryon-baryon collisions. We have identified a three-body screening mechanism which strongly reduces the subsequent absorption of antiprotons in the medium. We have used a relativistic cascade code to study this effect, and find that it is essential to obtaining good agreement with recent p¯ production data from Brookhaven experiment E802.

Effects of CIB (charge independence breaking) and CSB (charge symmetry breaking) interactions on the Coulomb displacement energies of isobaric analog states are investigated for ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The mass number dependence of the Coulomb energy anomalies is well explained when we employ CIB and CSB interactions which reproduce the differences of the scattering lengths as well as those of the effective ranges of low energy nucleon-nucleon scattering.

The quasielastic scattering of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at 60 MeV/nucleon is calculated in a four-body Glauber approximation. Different ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ ground-state wave functions are used, including those calculated using Faddeev three-body models. The calculated quasielastic cross sections, including the $2^{+}$ and $3^{\mathrm{-}}$ states of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ in a distorted wave Born approximation, reproduce the experimental data over most of the angular range, the differences between theoretical models being less than the quoted statistical errors on the available data.

Using separable NN and ΛN-ΣN potentials in the Faddeev equations, we have demonstrated that the predicted enhancement in the Λd cross section near the Σd threshold is associated with resonance poles in the scattering amplitude. The positions of these poles, on the second Riemann sheet of the complex energy plane, are determined by examining the eigenvalues of the kernel of the Faddeev equations. This suggests that for a certain class of ΛN-ΣN potentials we can form a Σ hypertriton with a width of about 8 MeV.

The level scheme of ${}_{}{}^{123}{}_{}{}^{}\mathrm{I}$ has been studied by in-beam gamma-ray spectroscopy in the fusion evaporation reaction ${}_{}{}^{121}{}_{}{}^{}\mathrm{Sb}$(α,2nγ${)}^{123}$I. Gamma-gamma coincidences and gamma-ray angular distributions have been measured with large-volume high-resolution germanium detectors. The multipolarities and multipole mixing ratios have been determined for some of the transitions. Several new levels and transitions are observed and assigned to ${}_{}{}^{123}{}_{}{}^{}\mathrm{I}$. A revised decay scheme is presented showing new levels and transitions associated with various bands in ${}_{}{}^{123}{}_{}{}^{}\mathrm{I}$. The band structure of ${}_{}{}^{123}{}_{}{}^{}\mathrm{I}$ is discussed and interpreted in the light of theoretical predictions and evidence is presented for possible coexistence of different shapes in this nucleus.

The lifetimes of the lowest $3^{\mathrm{-}}$ and $1^{\mathrm{-}}$ states in ${}_{}{}^{148\mathrm{-}152}{}_{}{}^{}\mathrm{Sm}$ have been determined employing the gamma-ray-induced Doppler broadening technique. The B(E1;$3^{\mathrm{-}}$→$2^{+}$) transition rates are compared to the corresponding B(E1;$1^{\mathrm{-}}$→$0^{+}$) values and interpreted in the framework of the interacting boson approximation sdf model. The qualitative behavior of these absolute transition rates can be understood in a simple physical picture by considering only the one-body part in the E1 transition operator. A more complex form including two-body terms is needed to explain simultaneously all available experimental data related to these levels.