Particle-particle correlations are studied for large- and small-angle separations for the reactions 312 and 680 MeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{\mathrm{nat}}$Ag. The spectral shapes and angular ansiotropies allow a characterization of the effective temperatures and spin zones of the hot nuclear emission sources. Small-angle correlations are compared to reaction simulations that employ various parametrizations for the emission time scales. We conclude that the initial lifetime scale for ${}_{}{}^{1,2,3}{}_{}{}^{}\mathrm{H}$ particle evaporation is of the order of ${10}^{\mathrm{-}22}$ s. These times are so short as to suggest a breakdown of the concept of ‘‘sequential evaporation,’’ for which a new ansatz is explored.

High-energy photon yields from the reactions ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{112,124}$Sn at 10 MeV/nucleon have been measured. The ratio of cross sections (${\mathit{E}}_{\gamma }$≥30 MeV)σ${(}^{124}$Sn)/σ${(}^{112}$Sn) is 1.6±0.2, which is larger than expected within the equal-participant model. The elementary n-p-γ cross section is evaluated within the neutral scalar σ meson exchange model, and implemented into a BUU code. The results of the BUU calculation suggest that the high-energy γ-ray yield differences for the two Sn isotopes arise from the differences in nucelon phase-space distributions. The sensitivity of the high-energy photon production to the initial phase-space conditions is explored.

Target residues from the interaction of copper with 90 MeV/nucleon ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ ions have been studied utilizing thick-target, thick-catcher recoil range techniques. Cross sections, average forward ranges, and forward-to-backward ratios have been measured. Isobaric and mass yield distributions have been constructed from the cross section data. Longitudinal momentum transfer information has been obtained. Comparison with a variety of lighter and heavier projectiles interacting with copper have been made. Comparisons of the data with initial interaction-evaporation models ISABELLE-EVA, BUU-GEMINI, and BUU-PACE are presented.

Dielectron production in p+d and p+p collisions at the beam kinetic energy of 4.9 GeV has been measured with the Dilepton Spectrometer. Features of the dielectron cross section have been studied with cuts on the mass and transverse momentum of the pairs. The spectra for several regions of phase space are presented as a function of the pair mass and transverse momentum.

The inclusive vector analyzing power ${\mathit{iT}}_{11}$ of ${\mathrm{\pi }}^{+}$${\to }^7$Li elastic scattering and inelastic scattering to the 0.47 MeV excited state was measured at several angles for ${\mathit{T}}_{\mathrm{\pi }}$=134, 164, and 194 MeV. The polarization effects were found to be small but nonzero, the trend of the data is well described by a coupled channels calculation. The results of the calculation are more sensitive to variations of the nuclear structure input than to variations of the reaction mechanism.

An optical method to determine the low-energy separation (1±4 eV) of nearby nuclear states of ${}_{}{}^{229}{}_{}{}^{}\mathrm{Th}$ is presented. It is shown that the Coulomb field of a deexciting electron of the ${}_{}{}^{229}{}_{}{}^{}\mathrm{Th}$ atom can cause transition between the near-lying nuclear states if the atom emits a photon with an energy equal to the difference between the energies of the electron and nuclear transitions. It is also predicted that the process can be enhanced through induced emission by applying a laser of resonant photon energy. The transition probabilities per unit time of the spontaneous and the laser induced processes are given.

The spectra of inclusive transfer reactions induced by heavy ions and leading to continuum final states show high-lying broad resonancelike structures superimposed on a large continuum. Recent experimental spectra for neutron stripping on targets in the lead region are analyzed by the Bonaccorso and Brink single-particle transfer model. The results of the calculation suggest that the structures are due to the population of high-spin single-particle states which are unbound and mix with the underlying states giving rise to a broadening of the peak. The main characteristics of the spectra are reproduced. Moreover, an estimate of the elastic and inelastic breakup contributions to the inclusive spectra is given.

We consider recent experimental data on azimuthal distributions of particles seen in heavy-ion collisions at 35 MeV/nucleon and at 50 MeV/nucleon. For ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at 50 MeV/nucleon laboratory energy, the distribution shows features characteristic of flow; for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ on ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ experimental data show features characteristic of rotation. For ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ on ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$ at 35 MeV/nucleon, effects of both flow and rotation are seen. In magnitudes the effects are small. We find that Boltzmann-Uehling-Uhlenbeck calculations are able to reproduce these results.

The cross sections for the p(e,e’${\mathrm{\pi }}^{+}$)n and d(e,e’${\mathrm{\pi }}^{+}$)2n reactions are calculated using a simple model with pion, nucleon and Δ-resonance degrees of freedom, for the kinematical conditions used in a recent Saclay experiment. The final-state interactions between the two outgoing neutrons are found to have a large effect on the d(e,e’${\mathrm{\pi }}^{+}$)2n reaction. The calculated quenching of the ${\mathrm{\pi }}^{+}$ production cross section for deuterium is in agreement with that observed experimentally. It is predicted that, due to the strong final-state interaction in the singlet S state of the two neutrons, the e,e’${\mathrm{\pi }}^{+}$ cross-section can have a large dependence on the orientation of deuteron spin. In principle this dependence can be observed with tensor polarized deuterium targets under suitable kinematical conditions.

We present classical and quantum approaches to light-particle correlations. The calculations are compared with p-p and p-d correlation functions measured at backward angles in the reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{108}$Ag at 44 MeV/nucleon. The predictions of both classical and quantum models are found to be in good agreement with experimental data. The extracted values of the mean time delay between emissions of two particles are (2.0±0.5)×${10}^{\mathrm{-}21}$ s for p-p and (3.5±1.5)×${10}^{\mathrm{-}21}$ s for p-d pairs. The differences between the two approaches became significant for emission time scales shorter than ${10}^{\mathrm{-}21}$ s. In this case the classical model predicts a noticeable influence of the Coulomb field of the emitter on the p-d correlation function. On the other hand, the quantum calculation shows an increasing importance of the two-particle nuclear interaction.

A parity violating (PV) meson exchange model is applied in the coupled channels formalism to study the effect of isobar excitation on PV pp scattering. The meson-mixing model used to calculate PV forbids the mixing of S=0 mesons in particular pions, as well as isospin symmetry violation, so only the ${\mathit{pa}}_1$ contribution is considered in isobar excitation. We find a significant contribution to A${\mathrm{¯}}_{\mathit{L}}$ from the PV mixing of the states ${}_{}{}^3{}_{}{}^{}$${\mathit{P}}_2$ and ${}_{}{}^1{}_{}{}^{}$${\mathit{D}}_2$ already at relatively low energies versus one (vector) meson exchange which gives predominantly ${}_{}{}^3{}_{}{}^{}$${\mathit{P}}_{0\mathrm{-}}^1$${\mathit{S}}_0$ mixing. At the energy of 230 MeV, where a forthcoming TRIUMF experiment aims to extract the parity violating ρpp coupling, our calculated effect from this source alone is of the same order as from the conventional single ρ exchange.

We show a possible large spin polarization of nuclei produced by one-nucleon transfer reactions predicted by the direct reaction theory. We investigate its origins in terms of the magnetic-sub-state cross sections by decomposing those into near-side and far-side components. The asymmetry of the particle-γ angular correlation followed by decay of the spin-polarized nucleus is also calculated.

We have obtained the first experimental evidence of the washing out of the collective level density enhancement associated with the amma deformation of the triaxial first barrier in the U isotope cross sections at neutron energies up to ∼20 MeV, with a statistical model which uses level densities obtained from Nilsson model singles particle levels, we find that it is necessary to (1) wash out the triaxial level density enhancement at an excitation energy of ∼7 MeV above the triaxial barriers with a width of ∼1 MeV, and (2) incorporate the effects of preequilibrium emission. These results imply a γ deformation of the first barriers in the range 10°–20°. Above an incoming neutron energy of ∼20 MeV where insufficient data exist to constrain optical model potentials, our statistical model U(n,f) cross sections increasingly overestimate the experimental data. A satisfactory reproduction of all the available U(n,f) cross sections above ∼20 MeV is obtained by scaling our calculated compound nucleus formation cross sections. This scaling factor falls from 1.0 at ∼20 MeV to 0.82 at 100 MeV.

Higher order effects in the electromagnetic excitation with fast nuclei are investigated in a systematic way. Since first order (one photon exchange) processes are dominant, a perturbation approach seems appropriate. After a general framework, which is elaborated especially for second order effects, the excitation of ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{Cl}$ is discussed as typical examples for an astrophysical application. We find that the method of Coulomb dissociation is in general not affected by higher order effects. The influence of the electromagnetic excitation mechanism on the apparent line shape of the one- and two-phonon giant dipole resonance is studied.

We calculate the dynamic polarization potential for ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ scattering from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at 637 MeV using both two- and three-body descriptions of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ structure and the Glauber theoretical treatment of the scattering and breakup processes. We conclude that the recent observation of Mermaz, that the quasielastic scattering data for this system require a ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ optical potential with long range attractive surface terms in the real and imaginary parts of the interaction, cannot be attributed to inelastic excitation and breakup of the weakly bound neutron halo. Such a strong surface attraction is difficult to reconcile with the best few-body description of the reaction where the real part of the dynamic polarization potential is found to be consistently repulsive in the far nuclear surface over a wide range of theoretical inputs.

Within the relativistic plane-wave impulse approximation, the sensitivity of complete sets of quasielastic proton-nucleus spin observables is investigated with respect to relativistic effects, the importance of exchange contributions to the NN amplitudes, the form of the πN vertex, and spin-orbit distortions. Calculations are performed at laboratory energies ranging from 135 to 500 MeV and for target nuclei ranging from ${\mathrm{C}}^{12}$ to ${\mathrm{Pb}}^{208}$ at a fairly large fixed momentum transfer of 1.97 ${\mathrm{fm}}^{\mathrm{-}1}$. Of all the spin observables, only ${\mathrm{A}}_{\mathrm{y}}$ exhibits a clear relativistic effect at the highest energy, as has been previously found. However, at the lower energies (200 MeV and below) the relativistic effect shifts to two other polarization transfer observables, mainly ${\mathrm{D}}_{\mathrm{s}\prime \mathrm{s}}$ and to a lesser extent ${\mathrm{D}}_{\mathrm{l}\prime \mathrm{s}}$. In addition, it is found that ${\mathrm{D}}_{\mathrm{n}\prime \mathrm{n}}$ is extremely sensitive to the pseudoscalar versus pseudovector ambiguity of the πN vertex, whereas ${\mathrm{D}}_{\mathrm{s}\prime \mathrm{l}}$ and ${\mathrm{D}}_{\mathrm{l}\prime \mathrm{l}}$ are sensitive to exchange contributions to the NN amplitudes. Compared to the latter, the effects of spin-orbit distortion are not insignificantly small and had to be corrected for. This investigation stresses the urgent need for measurements of the quasielastic spin observables at these low energies.

By means of the thermofield dynamical theory, the effective mass of omega meson is calculated by summing the bubble diagrams. It is found that the formula for the effective mass of the ρ meson can also be used to describe the ω meson in the low density region, but the parameter n and the critical temperature ${\mathit{T}}_{\mathit{c}}$ depend on the density. The temperature and density dependence of one omega exchage potential of nucleon-nucleon interaction are given. The conjecture of Brown and Rho about the effective masses of mesons is discussed.

We calculate elementary proton-proton and neutron-proton bremsstrahlung and their contribution to the ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ invariant mass distribution. At 4.9 GeV, the proton-proton contribution is larger than neutron-proton, but it is small compared to recent data. We then make a first calculation of bremsstrahlung in nucleon-nucleon reactions with multihadron final states. Again at 4.9 GeV, the many-body bremsstrahlung is larger than simple nucleon-nucleon bremsstrahlung by more than an order of magnitude in the low-mass region. When the bremsstrahlung contributions are summed with Dalitz decay of the η, radiative decay of the Δ and from two-pion annihilation, the result matches recent high statistics proton-proton data from the Dilepton Spectrometer collaboration.

Detailed-balance tests of time-reversal invariance (TRI) with charged-particle resonance reactions are reexamined from the view that there may be large enhancement of TRI violation near two interfering resonances. In our proton resonance data on ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$, ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$, and ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ targets, there are 41 pairs of adjacent resonances with the same angular momentum and parity. Using experimental resonance parameters, the difference in the differential cross sections for the (p,${\mathrm{\alpha }}_0$) and (α,${\mathit{p}}_0$) reactions was calculated for each of these resonance pairs. An appropriate figure-of-merit involving both the difference of the two cross sections and the magnitudes of the cross sections was determined for each resonance pair. Both the differences and the figures-of-merit show very strong dependence on energy, angle, and the particular pair of resonances; the relative sensitivity varies by many orders of magnitude. These results suggest that suitably chosen charged-particle resonance tests of TRI violation would be much more sensitive than previous detailed-balance tests.

Negative pion spectra emitted in the reactions of 775 MeV/nucleon ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$${+}^{12}$C and ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$${+}^{139}$La reactions have been measured in coincidence with the projectile fragments using the HISS spectrometer at the Bevalac. Prominent peaks near the beam velocity were observed in the pion spectra. Position and widths of the peaks were studied as a function of the ‘‘sum charge’’ of projectile fragments which is a good measure of impact parameter; the smaller the ‘‘sum charge,’’ the smaller the impact parameter. The peak position down shifts with the smaller ‘‘sum charge.’’ The pion peak is wider in the transverse than in the longitudinal direction, possibly mirroring the velocity dispersions of projectile fragments in the early stage of reactions.