The method of two-pion interferometry was used to obtain source-size and lifetime parameters for the pions produced in heavy ion collisions. Two acceptances (centered at approximately 0° and approximately 90°, in the center of mass) were used for each of three systems, 1.70 GeV/nucleon ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$+Fe, 1.82 GeV/nucleon ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$+KCl, and 1.54 GeV/nucleon ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$+Nb, allowing a search for dependences on nuclear mass and viewing angle. The correlation functions were calculated by comparing data samples to event-mixed reference samples. The effect of the particle correlations on the reference samples was corrected by weighting the events appropriately to remove the residual correlation effect. The source parameters, in the nucleus-nucleus center-of-mass frame, show an oblate source (i.e., ${\mathit{R}}_{\mathrm{\perp }}$>${\mathit{R}}_{\mathrm{\parallel }}$) for the lighter systems and an approximately spherical source for the heaviest system. The dependence on nuclear mass shows that ${\mathit{R}}_{\mathrm{\perp }}$ is essentially constant (under both viewing angles), whereas ${\mathit{R}}_{\mathrm{\parallel }}$ for the 90° (c.m.) data increases with the nuclear mass. No evidence was found for a dependence of the source size on the pion momentum.

Cross sections for emission of complex fragments (Z>2) in their ground and excited states are presented for the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${+}^{58}$Ni at a bombarding energy of 630 MeV. Measurements of energy spectra, angular distributions, and angle-integrated cross sections were made for fragments of Z=4 to 20. γ rays emitted in coincidence with the fragments were measured in a 4π geometry using 62 NaI detectors and 8 Compton-suppressed germanium detectors. Data presented are mostly for the cross sections extracted by γ-ray techniques. A simple statistical approach to associate the ratio of cross sections for excited states and ground states to the temperature of the emitter fails to give the expected temperatures. However, it is shown that this is mostly due to the fact that the fragments that γ decay are secondary fragments produced by particle decay of the primary fragments. A Hauser-Feshbach analysis accounts well for the fragment cross sections, energy spectra, and extracted temperatures, provided that evaporation from the primary fragments is included.

We have measured the transverse momentum of protons as a function of rapidity in 50 MeV/nucleon C-induced peripheral collisions with C and Au targets. The reaction plane for each event was determined from the azimuthal angle of lightly damped coincident projectile fragments. High transverse momentum protons in the midrapidity region were found to be deflected towards the opposite side of the reaction plane with respect to the beam axis than the projectile fragments. This result is interpreted as projectile fragment scattering to positive angles due to the repulsive Coulomb interaction while midrapidity protons are simultaneously deflected to negative angles by the attractive component of the nuclear mean field.

Measurements of angular distributions for elastic scattering in the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ system were performed in the energy range from 15 to 40 MeV c.m. in ≃2.5 MeV steps in broad angular regions up to about ${170}^{\mathrm{°}}$ c.m. The optical-model parameters were determined from the analysis of the cross section at forward angles. The rise of cross section in the backward angles was explained as direct elastic transfer. From the distorted-wave Born approximation analysis, the values of proton spectroscopic factor in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ were found. They exhibit a strong energy dependence in the energy region between 5 and 40 MeV c.m.

Charged pions and light nuclei (p, d, t, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$) have been measured in the interaction of proton beams with C, Nb, and Pb targets at 0.8 and 1.6 GeV incident energies, using a large solid angle detector. From slices on the multiplicity of protonlike particles (free protons and protons bound in light fragments), the events have been sorted out into two classes corresponding to more peripheral and more central collisions. For each class of events, the mean value and the dispersion of the ${\mathrm{\pi }}^{+}$ and ${\mathrm{\pi }}^{\mathrm{-}}$ multiplicity distributions have been studied as a function of target mass and incident energy. Comparisons to the Liege intranuclear cascade predictions exhibit some discrepancies which are discussed.

The elastic-scattering angular distribution of p${+}^{11}$Li at ${\mathit{E}}_{\mathrm{lab}}$=100 MeV is evaluated within Glauber’s theory. The p${\mathrm{-}}^{11}$Li optical potential is evaluated within the ‘‘tρ’’ approximation with ${\mathrm{\rho }}^{11}$Li, the matter density of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$, calculated within constrained Hartree-Fock theory. Medium effects on the nucleon-nucleon t matrix, are fully taken into account. The effect of the halo neutrons on dσ/dΩ is assessed through comparison with the p${+}^{12}$C and p${+}^9$Li systems at ${\mathit{E}}_{\mathrm{lab}}$=100 and 800 MeV.

We study the origin of the transverse momentum distribution in heavy-ion collisions within a relativistic transport approach. To achieve a better understanding of the reaction dynamics, we decompose the total ${\mathit{p}}_{\mathit{t}}$ distribution into a mean-field, N-N collision, and Fermi-momentum part. We find that the origin of the transverse momentum strongly depends on the rapidity region. Our investigation of the impact-parameter and mass dependence suggests that peripheral collisions may be useful to investigate the momentum dependence of the mean-field in the nucleus-nucleus case, whereas the mass dependence could give hints about the N-N-collision part. Only after these two issues are settled it may be possible to extract information about the density dependence in central collisions, which may, however, necessitate reactions at even higher energies than the 800 MeV/nucleon considered in this work.

Full-folding model calculations of proton elastic scattering at intermediate energy made using the free off-shell NN t matrix and including the variation of the energy in the NN center of mass as prescribed by the full-folding model are compared with similar calculations using t matrices evaluated at a fixed energy. The fixed energy is chosen on the basis of the incident beam energy ignoring the Fermi momentum of the struck target nucleon. Near 200 MeV, the energy prescription for the NN matrix is found to be responsible for much of the difference between recently reported full-folding calculations as well as for the differences between full-folding calculations and conventional tρ approximations to them. The sensitivity of the scattering observables to the starting energy suggests that at lower intermediate energies, explicit medium corrections should be included in applications of the full-folding model.

In the near-threshold region for the (γ,${\mathrm{\pi }}^{\pm }$) reaction the spin-flip (Kroll-Ruderman) term dominates most nuclear reactions. The smaller non-spin-flip term is of considerable interest because it is very sensitive to the reaction dynamics and in particular to the Δ channel, even in the near-threshold region. We propose to study the non-spin-flip term via the $0^{+}$→$0^{+}$ transition in the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$(γ,${\mathrm{\pi }}^{\mathrm{-}}$${)}^{14}$N reaction; the cross section is shown to be insensitive to the details of nuclear structure at low momentum transfer Q≤0.5 ${\mathrm{fm}}^{\mathrm{-}1}$.

The Frenkel-Dirac variational principle is generalized for systems out of thermal equilibrium. This allows us to obtain mean-field equations. With a simple parametrization one can write equations which resemble hydrodynamics for irrotational compressible fluids. The method is applied to a simple example.

Using large-basis realistic wave functions for ${}_{\mathrm{\Lambda }}{}^7{}_{}{}^{}\mathrm{Li}$ ${(}_{\mathrm{\Lambda }}^7$He) hypernuclei, details of the production mechanisms in (${\mathit{K}}^{\mathrm{-}}$,${\mathrm{\pi }}^{\mathrm{-}}$), (${\mathrm{\pi }}^{+}$,${\mathit{K}}^{+}$), and (γ,${\mathit{K}}^{+}$) processes are displayed, compared, and discussed. In particular, a selective but complementary population of different parts of spectra in these three reactions and a competition between the resolution and applicability of the realistic spectra are demonstrated. Different polarization abilities of the studied reactions are illustrated and optimal kinematical regions are sought, as well.

Based upon a consistent description of the wave functions of the captured state and the final state, a unified formalism has been established to investigate the nonstatistical effects in radiative nucleon capture reactions at energies ranging from 0.1 to 20 MeV. This model includes the direct-semidirect capture and radiative capture in the compound elastic and inelastic channels. By applying this model theory and including also the statistical contributions of the compound-nucleus process, the radiative neutron capture cross sections in ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{55}{}_{}{}^{}\mathrm{Mn}$, ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ have been calculated and the results are compared with the measured data. We have also investigated the relative importance of the operation for each nonstatistical mechanism in the total capture cross sections.

In this paper, both the phenomenological and microscopic neutron relativistic optical potentials are presented. The global neutron relativistic phenomenological optical potential (RPOP) based on the available experimental data for various nuclei ranging from C to U with incident energies ${\mathit{E}}_{\mathit{n}}$=20–1000 MeV has been obtained through an automatic search of the best parameters by computer. Then the nucleon relativistic microscopic optical potential (RMOP) is studied by utilizing the effective Lagrangian based on the popular Walecka model. Through comparison between the theoretical results and experimental data we shed some insight into both the RMOP and RPOP. Further improvement concerning how to combine the phenomenological potential with the microscopic one in order to reduce the number of free parameters appearing in the RPOP is suggested.

Sum rules for inelastic electron scattering from a composite system are derived within the framework of light-front dynamics. The underlying assumptions are similar in spirit to those used to derive the nonrelativistic Coulomb sum rule. The light-front sum rule yields parton model sum rules in the limit that the constituents are structureless Dirac particles. The connection to the Coulomb sum rule is discussed.

We consider the question what constitutes a good signature for the occurrence of an intermediate phase transition in a many-body system. In the context of a simple model for a chiral phase transition we show that, in principle, no rigorous signal for a temporary phase change exists in a finite system. We discuss the relevance of our result to the question of what constitutes an unambiguous signature for the formation of a quark-gluon plasma in relativistic nuclear collisions.

We introduce the coalescence variables, a set of three boost-invariant kinematic quantities that may be used in analyzing n-particle correlations. These variables characterize the invariant mass of an n-particle system, and in three directions separate the timelike and spacelike characteristics of the source. The analytic Kolehmanien-Gyulassy model is generalized to give two-, three-, and four-particle correlation functions, with coherence and Coulomb corrections applied to the basic formalism. We demonstrate the relation of the coalescence variables to the radius and duration of the source, and find that for sufficiently large transverse radii, Coulomb effects can suppress the structure of the Hanbury-Brown–Twiss correlations so that no significant information on source size can be obtained.

We explore the development of a nontopological soliton model for baryons in which effective meson fields are generated from extended quark-antiquark pairs within a nonlocal model of Nambu–Jona-Lasinio type. Meson kinetic and potential energies arise from the Dirac sea. Only scalar-isoscalar and pseudoscalar-isovector meson fields are retained. Functional methods and bilocal field techniques are employed and we work to lowest order in loops for the retained degrees of freedom. We identify a mean-field approximation from the effective action obtained through a Legendre transformation incorporating a chemical-potential constraint. This fixes the baryon number in terms of valence quark configurations and thereby induces a classical configuration for the meson fields. After a localization of the meson sector of the effective action, the model is of the linear sigma type with a nonlocal quark-meson vertex due to the composite extended nature of the internally generated meson fields. With a self-confining dynamical quark mass, the classical meson fields provide a region where quarks can propagate and have a defined eigenenergy. A simple model illustration of this mechanism is provided.

A relativistic two-level convolution model for deep-inelastic lepton nucleus scattering is presented in which the target nucleus is considered as a composite system of baryon-mesons which are also composite systems of quark-gluons, with each level based on the light-cone quantum field theory, respectively. In this prescription the impulse approximation is justified, the baryon number conservation is naturally guaranteed, and the off-shell ambiguity in the nucleonic approach is fixed. The scaling variable for bound nucleons is derived in a realistic way from the constraint of overall ‘‘energy’’ conservation, and a two-level convolution formula for nuclear-structure functions is given. It is shown that the European Muon Collaboration effect seems unable to be explained by the off-shell effect in terms of nucleonic degrees of freedom alone in this prescription.

We report the relative polarization of the ${\mathit{P}}_{\mathit{F}}$/${\mathit{P}}_{\mathrm{GT}}$=0.9996±0.0037 for the positrons emitted by the pure Fermi ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}$ and the pure Gamow-Teller ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$ decays, using a technique based on the observation of the positronium-decay time spectrum. The radioisotopes to be compared are part of the same source, eliminating some of the potential systematic errors which may vitiate relative polarization measurements of high precision. Combining our result with a similar ${}_{}{}^{26}{}_{}{}^{}\mathrm{Al}_{}^{\mathit{m}}{}_{}{}^{}$${/}^{30}$P decay positron comparison obtained by Bhabha polarimetry, we deduce the following constraint on the product of the mixing angle ζ and mass-squared ratio δ of the chiral W bosons assumed in left-right symmetric models: -0.0004<ζδ<0.0007 (90% C.L.). Our result also constrains possible scalar and tensor admixtures to the dominant vector and axial-vector currents: ${\mathit{C}}_{\mathit{S}}$+C${\mathcal{’}}_{\mathit{S}}$/${\mathit{C}}_{\mathit{V}}$-${\mathit{C}}_{\mathit{T}}$+C${\mathcal{’}}_{\mathit{T}}$/${\mathit{C}}_{\mathit{A}}$ =0.003±0.018 (90% C.L.).

The hyperspherical harmonics method is used to solve the α+N+N three-body problem. The resulting wave functions and corresponding densities are, with satisfactory result, tested against a variety of weak and electromagnetic data as well as nucleon-induced quasielastic reactions (p,p’), (n,p), and (p,n) on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ as target. A procedure is outlined which generates reliable transition densities for the (projectile, ejectile) part of ${}_{}{}^6{}_{}{}^{}\mathrm{induced}$ inelastic and charge-exchange reactions A${(}^6$Li,b)B, b${=}^6$Li*,${\mathrm{}}^6$He, and ${}_{}{}^6{}_{}{}^{}\mathrm{Be}$.