A QCD-based treatment of projectile size fluctuations is used to compute inelastic diffractive cross sections ${\mathrm{\sigma }}_{\mathrm{diff}}$ for coherent hadron-nuclear processes. We find that fluctuations near the average size give the major contribution to the cross section with < few % contribution from small size configurations. The computed values of ${\mathrm{\sigma }}_{\mathrm{diff}}$ are consistent with the limited available data. The importance of coherent diffraction studies for a wide range of projectiles for high energy Fermilab fixed target experiments is emphasized. The implications of these significant color fluctuations for relativistic heavy ion collisions are discussed.

Differences between longitudinal and transverse two-proton correlation functions, consistent with finite lifetime effects, are observed for central ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$${+}^{45}$Sc collisions at E/A=80 MeV. The correlations between two protons emitted with low total momenta are consistent with emission from a source of Gaussian radius ${\mathit{r}}_0$≊4.7±0.3 fm and characteristic lifetime τ≊25±15 fm/c.

Dynamics of scattering in the classical model of α-cluster nuclei is studied in terms of transport theory. Behavior typical for hyperbolic chaotic scattering is found, which results in an exponential decay of the survival probability. This allows a determination of the unitarity deficit of the S matrix and thus the probability for compound-nucleus formation.

High resolution measurements of the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(γ,n) at ${\mathit{E}}_{\gamma }$∼58 MeV are presented. The distribution of strength to the resolved bound final states in ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ is compared with that of ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ obtained in previous analogous (γ,p) measurements and the implications for the theoretical description of (γ,N) reactions are discussed. These new results confirm the importance of two-nucleon effects in intermediate energy photon absorption and highlight inadequacies in state-of-the-art microscopic calculations of (γ,N) reactions.

In a high precision experiment, Mott scattering of the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$${+}^{108}$Pb system was measured at ${\mathit{E}}_{\mathrm{lab}}$=873.40 MeV and 1129.74 MeV with kinematic coincidences for angle pairs around ${\mathrm{\theta }}_{\mathrm{lab}}$=30°, 60° and ${\mathrm{\theta }}_{\mathrm{lab}}$=45°, 45°. The observed Mott oscillations exhibit an angular shift with respect to pure Mott scattering. A comparison with the angular shift produced by a color van der Waals force including nuclear polarizability, vacuum polarization, relativistic effects, and electronic screening provides a new upper limit for the strength of this force. Influence of atomic effects other than screening were identified for the first time.

Electromagnetic form factors for the ρπγ and ωσγ vortices, estimated from quark loop diagrams, differ considerably from the monopole form factors obtained from vector meson dominance, and significantly alter the predictions for the elastic electromagnetic form factors of the deuteron.

Relative intensities of the yrast and the first excited superdeformed bands in ${}_{}{}^{151}{}_{}{}^{}\mathrm{Tb}$ have been accurately measured, with the EUROGAM spectrometer. It is shown that he excited band depopulates at the same freqeuncy and spin as its identical band in the isotone ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ whereas the yrast band deexcites at higher rotational frequency and spin even though it is much lower in excitation energy. A classification of superdeformed bands in the A∼150 mass region indicates that the decay-out mechanism is strongly affected by neutron pairing correlations and the occupancy of high-N intruder orbitals.

The photonuclear reactions ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(γ,n${)}^{15}$O and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(γ,p${)}^{15}$N are simultaneously described within a coupled channels framework based on a continuum shell model formulation that includes all nonlocalities arising from antisymmetrization. This large-scale conventional many-body calculation provides a good description of the medium energy data. The inclusion of Δ(1232) degrees of freedom further, but slightly, improves the description of the available data. Complete quantitative agreement, however, is still lacking.

The characteristics of the fission step following a binary deep-inelastic interaction have been reconstructed for three-body events detected in the reaction ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$${+}^{100}$Mo at 18.7A MeV and ${}_{}{}^{12\mathrm{-}}{}_{}{}^{}\mathrm{Sn}$${+}^{120}$Sn at 18.4A MeV. The observed anisotropy of the in-plane angular distributions points to the fast decay of a rotating (and strongly deformed) nuclear object formed at the end of the deep-inelastic interaction. The derived time scale of the process indicates that asymmetric divisions are faster than symmetric ones.

${\mathit{K}}^{+}$-nucleus quasielastic cross sections measured for a laboratory kaon beam momentum of 705 MeV/c are presented for 3-momentum transfers of 300 and 500 MeV/c. The measured differential cross sections for C, Ca, and Pb at 500 MeV/c are used to deduce the effective number of nucleons participating in the scattering, which are compared with estimates based on the eikonal approximation. The long mean free path expected for ${\mathit{K}}^{+}$ mesons in nuclei is found. Double differential cross sections for C and Ca are compared to relativistic nuclear structure calculations.

Dipole transitions linking signature partner superdeformed bands in ${}_{}{}^{193}{}_{}{}^{}\mathrm{Hg}$ have been observed. Measurements of the photon decay branching ratios, taken together with the average superdeformed quadrupole moment measured in neighboring nuclei, enable the absolute M1 strengths to be determined. From these data, using the strong coupling model, we find (${\mathit{g}}_{\mathit{K}}$-${\mathit{g}}_{\mathit{R}}$)K/${\mathit{Q}}_0$=-0.14±0.01 (e b${)}^{\mathrm{-}1}$, ${\mathit{g}}_{\mathit{K}}$=-0.65±0.14 with Ω=2.8±0.8. These data are consistent with the superdeformed neutron orbital being [512]5/$2^{\mathrm{-}}$ as predicted by cranked Woods-Saxon calculations.

Systematic nuclear resonance fluorescence experiments, including model independent parity determinations, provided evidence for enhanced E1 excitations near 2.5 MeV excitation energy in the deformed nuclei ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}$, ${}_{}{}^{160}{}_{}{}^{}\mathrm{Gd}$, and ${}_{}{}^{162,164}{}_{}{}^{}\mathrm{Dy}$. The corresponding ${\mathit{J}}^{\mathrm{\pi }}$=$1^{\mathrm{-}}$ states are interpreted as two-phonon excitations due to the coupling of octupole (J=$3^{\mathrm{-}}$,K=1) and quadrupole γ vibrations (J=$2^{+}$,K=2). The results can be explained in the framework of the sdf interacting-boson-approximation model and the dynamic collective model describing octupole vibrations and their coupling to quadrupole vibrations in deformed nuclei.

We investigate πρ scattering in the pseudoscalar (π) and axial-vector (${\mathit{A}}_1$) channel. Our model based on s- as well as t-channel meson exchange can resolve apparent discrepancies occurring in the analysis of the axial-vector ${\mathit{A}}_1$ meson. Furthermore, it leads to an appreciable softening of the πNN form factor in agreement with information from other sources. This strong contribution in the pionic channel substantiates earlier claims that inclusion of correlated πρ exchange might allow the use of a soft πNN form factor in NN potential models and thus could resolve a long-standing puzzle.

Measurements have been made of Δ${\mathrm{\sigma }}_{\mathit{T}}$ for polarized neutrons incident on a polarized-proton target from 3.65 to 11.60 MeV. In the energy range near 10 MeV, Δ${\mathrm{\sigma }}_{\mathit{T}}$ is very sensitive to the nucleon-nucleon tensor interaction. Comparison of the data to potential-model predictions indicate that the tensor interaction is weak, resulting in values of the ${}_{}{}^3{}_{}{}^{}$${\mathit{S}}_1$${\mathrm{-}}^3$${\mathit{D}}_1$ mixing parameter ${\mathrm{\epsilon }}_1$ which are smaller than predicted by any nucleon-nucleon potential model. A smaller tensor force will bring the predictions of local potential models for the triton binding energy into closer agreement with the experimental value.

The disappearance of collective flow in nucleus-nucleus collisions occurs at an incident energy (${\mathit{E}}_{\mathrm{bal}}$) where the attractive scattering dominant at low energies balances the repulsive scattering dominant at high energies. We have performed the first systematic study of the entrance-channel mass dependence of the disappearance of flow and hence ${\mathit{E}}_{\mathrm{bal}}$. The new data presented for the C+C, Ne+Al, Ar+Sc, and Kr+Nb systems show that ${\mathit{E}}_{\mathrm{bal}}$ scales as ${\mathit{A}}^{\mathrm{-}1/3}$ where A is the mass of the combined system. Boltzmann-Uehling-Uehlenbeck model calculations show trends which are in qualitative agreement with these new results.

E3 matrix elements have been determined for transitions between states up to ${\mathit{I}}^{\mathrm{\pi }}$=${13}^{\mathrm{-}}$ in ${}_{}{}^{148}{}_{}{}^{}\mathrm{Nd}$, providing direct evidence for strong octupole collectivity in a rotational band. These values, as well as the corresponding E1 and E2 matrix elements, were obtained from Coulomb excitation data using ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ and ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ ions, projectile excitation using a ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ target, and from recoil distance lifetime measurements. The results are consistent with collective model predictions for ${}_{}{}^{148}{}_{}{}^{}\mathrm{Nd}$ assuming intrinsic quadrupole and octupole moments of ${\mathit{Q}}_{20}$≊400 e ${\mathrm{fm}}^2$ and ${\mathit{Q}}_{30}$≊1500 e ${\mathrm{fm}}^3$. The E3 strength coupling the negative-parity states to the β band is found to be appreciable.

Inclusive double-differential cross sections for 500-MeV pions are presented for C(${\mathrm{\pi }}^{\pm }$,${\mathrm{\pi }}^{\pm }$) at ${\mathrm{\theta }}_{\mathrm{lab}}$ of 30 °, 40 °, 50 °, 70 °, and 90 °; and for C(${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^{\mathrm{-}}$) at 110 °. We compare the 50 ° and 70 ° data with C(e,e’) data at nearly the same momentum transfer. These spectra from very different probes are more similar than expected from an intranuclear cascade calculation, which includes the strong rescattering of pions that have energies near 180 MeV. Agreement of the calculated spectra and the pion data is improved if the nucleus is assumed to be nearly transparent to these pions.

The superdeformed (SD) structure of ${}_{}{}^{150}{}_{}{}^{}\mathrm{Gd}$ has been studied using the Eurogam gamma-ray spectrometer and three new SD bands have been discovered. An interaction is observed between two of the SD bands caused by the near degeneracy of two levels. This is the first observation of accidental degeneracy between SD states. The interaction strength is determined to be 11 keV and evidence for crosstalk between the bands is observed. The absolute energy difference between two SD states in the second minimum has been accurately measured and the relative spins and parities of the two bands have been fixed.

A novel interpretation of nuclear rotation is presented. It is shown that, in and near the ground state, the proton and neutron deformed ellipsoids are rotating in opposite directions, whereas they rotate about almost the same axis in states of higher spins. This holds, quite similarly, for angular-momentum-projected Nilsson wave functions and for wave functions in the interacting boson model. The rotational energy can then be interpreted in terms of an inertial parameter against tilting of the proton rotation axis towards the neutron axis.

We have performed accurate G-matrix calculations for the hypernucleus ${}_{\mathrm{\Lambda }}{}^{16}{}_{}{}^{}\mathrm{O}$ using the one- and two-boson-exchange Jülich hyperon-nucleon potentials. A finite-nuclei Pauli operator defined in terms of oscillator wave functions is employed, and treated essentially exactly in solving the coupled ΛN and ΣN G-matrix equation. Numerical stability concerning the choice of the k-space mesh points for discretization and the accuracy of a finite-boundary approximation are examined. Our calculated spectrum for ${}_{\mathrm{\Lambda }}{}^{16}{}_{}{}^{}\mathrm{O}$ is in good agreement with experiments.