We have implemented multistep compound (MSC) and multistep direct (MSD) preequilibrium theories of Feshbach, Kerman, and Koonin (FKK) for the calculation of nucleon-induced reactions. Unlike most previous analyses, which have concentrated on just one of these multistep mechanisms, we consider both mechanisms as well as subsequent Hauser-Feshbach equilibrium emission, and describe the complete nucleon emission spectra and angular distributions quantum mechanically. We compare theoretical calculations of (n,n’) and (n,p) reactions on ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$ at energies of 14, 20, and 25.7 MeV with experimental data. Our analysis suggests that the FKK theory should be modified to allow transitions from the MSD to MSC preequilibrium chains, and shows MSC processes to be less important than previously thought. We find that the MSD mechanism dominates preequilibrium emission even for incident neutron energies as low as 14 MeV. A model to account for preequilibrium flux cascading from the MSD to MSC chain is presented, and we check its validity with a least-squares fit to data which establishes the experimentally observed partitioning between MSD and MSC.

A simple model is used to explore issues related to self-similarity, intermittency, and scaling behavior in nuclear collisions. Both scaled factorial moments and power moments are considered in the investigation of these features. The product mass yields are used to construct probability distributions and generalized Renyi entropies. The scaling properties of the resulting Renyi entropies are studied. Both exponential and power law behavior are found. A discussion of dimensions associated with these scaling properties is also given. An analysis of some experimental data is presented.

The electromagnetic creation of various exotic particles in ultrarelativistic heavy-ion collisions is discussed. The production of intermediate mass Higgs bosons of the minimal supersymmetric extension of the standard model is enhanced over the standard model Higgs boson formation for certain model parameter choices and as a consequence might be detectable at the CERN Large Hadron Collider and Superconducting Super Collider. We also investigate the electromagnetic generation of supersymmetric fermions and bosons as well as glueballs, mesons, and fermions.

Strangeness production at the CERN Super Proton Synchrotron energies is studied within the quark-gluon string model. The observed shape of rapidity and transverse mass distributions are reproduced fairly well for both peripheral and central heavy ion collisions. However, for central collisions the model underpredicts strange particle abundances by a factor of about 2:2:4 for ${\mathit{K}}_{\mathit{S}}^0$, Λ, and Λ¯, respectively. This discrepancy can be considered as a possible manifestation of collective string-string interactions similar to the formation of a color rope. Model predictions for coming experiments with the Pb beam at CERN are given.

The cross section for the electromagnetic production of different particles in heavy-ion collision is derived within the external field approach. Introducing polarized photon-fusion cross sections, it is possible to generalize the equivalent photon method to describe the impact-parameter dependence of the particle production. The impact-parameter dependent production of scalar and pseudoscalar (spin 0) bosons, charged (spin 0) boson pairs, and fermion pairs is discussed.

Requirements for correlation measurements in high-multiplicity events are discussed. Attention is focused on detection of so-called hot spots, two-particle rapidity correlations, two-particle momentum correlations (for quantum interferometry), and higher-order correlations. The signal-to-noise ratio may become large in the high-multiplicity limit, allowing meaningful single-event measurements, only if the correlations are due to collective behavior.

The early evolution of the gluon plasma produced in ultrarelativistic nuclear collisions is investigated via chromoviscous hydrodynamics. The initial conditions are determined by perturbative QCD minijet production including nuclear shadowing of the parton distributions. The analog of Ohmic heating is shown to damp rapidly any chromoelectric fields in the plasma. In the context of the flux tube models for beam jet fragmentation this damping is shown to suppress pair production processes, decrease transverse energy production, and reduce the quark-gluon chemical equilibration rate. Possible implications for dilepton production are noted.

Relativistic chiral models with a light scalar meson appear to provide an economical marriage of successful relativistic mean-field theories and chiral symmetry. The scalar meson serves as both the chiral partner of the pion and the mediator of the intermediate-range nucleon-nucleon (NN) attraction. However, while some of these models can reproduce the empirical nuclear matter saturation point, they fail to reproduce observed properties of finite nuclei, such as spin-orbit splittings, shell structure, charge densities, and surface energetics. These deficiencies imply that this realization of chiral symmetry is incorrect. An alternative scenario, which features a heavy chiral scalar and dynamical generation of the NN attraction, is discussed.

By using the partially conserved axial-vector current hypothesis and the electromagnetic current conservation law, we calculate transverse and longitudinal multipoles for threshold pion electroproduction on the nucleon. We include off-shell form factors for the axial-vector current, the electromagnetic current, and the pion-nucleon vertex. We confirm that if the electromagnetic off-shell form factors are assumed to be finite in the chiral limit of the vanishing pion mass, the low-energy theorems are unaffected by them. However, we show that if one of these form factors has simple-pole singularity in the chiral limit, it shows up in the threshold amplitudes at next-to-leading order predicted by the low-energy theorems.

We study the scalar-isoscalar sector of the Nambu–Jona-Lasinio (NJL) model and extend the model to include a description of the coupling of the quark-antiquark states to the two-pion continuum. The qq¯ interaction gives rise to a sigma meson, which takes on a width and energy shift that depends upon the strength of the coupling for q+q¯→π+π. (For weak channel coupling, the resonance is located at the mass of the sigma, ${\mathit{m}}_{\mathrm{\sigma }}$≃2${\mathit{m}}_{\mathit{q}}^{\mathrm{cons}}$, where ${\mathit{m}}_{\mathit{q}}^{\mathrm{cons}}$ is the constituent quark mass of the NJL model.) We consider two models for the qq¯→ππ coupling. In the first model, we find a low-energy resonance, with the resonance energy ${\mathit{E}}_{\mathit{R}}$≤2${\mathit{m}}_{\mathit{q}}^{\mathrm{cons}}$. We then see that the values, obtained from the analysis of experimental data, of the scalar-isoscalar phase shift describing ππ scattering ${\mathrm{\delta }}_0^0$, are not compatible with the existence of a low-mass sigma. In the second model, the resonance is pushed upward into the region of the two-quark continuum, ${\mathit{E}}_{\mathit{R}}$>2${\mathit{m}}_{\mathit{q}}^{\mathrm{cons}}$. This second model provides an example of a phenomenon where the behavior of the qq¯ T matrix is parametrized for ${\mathit{q}}^2$≤0 by a mass that is smaller than the physical mass that characterizes the pole in the T matrix. The behavior of the second model suggests how the absence of experimental evidence for a low-mass sigma may be reconciled with the importance of such a meson in nuclear structure studies.

The P-odd and CP-odd nucleon potential for different models of CP violation in the one-meson exchange approximation is studied. It is shown that the main contribution is due to the π-meson exhcange which leads to a simple one-parameter CP-odd nucleon potential.

The rate for destruction of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ via deuteron-induced reactions is reexamined and is found to be appreciably larger than that previously used in primordial nucleosynthesis codes over most of the temperature region of interest. Numerous calculations were run to determine the significance of the new rate; it was found to change the predicted ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ abundance by not more than 20% over the parameter space examined.

Fusion evaporation-residue cross sections for the ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$${+}^{12}$C reaction have been measured in the energy range 18≤${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$≤136 MeV using time-of-flight techniques. Velocity distributions of mass-identified reaction products were used to identify evaporation residues and to determine the complete-fusion cross sections at high energies. The data are in agreement with previously established systematics which indicate an entrance-channel mass-asymmetry dependence of the incomplete-fusion evaporation-residue process. The complete-fusion evaporation-residue cross sections and the deduced critical angular momenta are compared with earlier measurements and the predictions of existing models.

An experiment was performed to measure the lifetimes of the states in the superdeformed band reported in ${}_{}{}^{192}{}_{}{}^{}\mathrm{Pb}$. No evidence for such a band was found, despite the fact that the experimental conditions were nearly identical to those of an earlier measurement where this band was proposed. The problems and questions encountered in the analysis are described. The arguments presented here indicate that further measurements are needed to establish the existence of a superdeformed band in this nucleus unambiguously.

In ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ interactions with nuclear emulsion at an energy of ≊1A GeV from the Bevatron at Lawrence Berkeley Laboratory, nuclei with Z up to 90 have been observed as a function of the associated proton multiplicity. With increasing centrality of the collisions—measured through the yield of proton multiplicity ${\mathit{N}}_{\mathit{p}\mathrm{—}}$the average number of intermediate-mass fragments 〈${\mathit{N}}_{\mathrm{IMF}}$〉 of charge 3≤Z≤35 first increases, attains a maximum value of 〈${\mathit{N}}_{\mathrm{IMF}}$〉=5.5 for the semicentral collisions and for the most central collisions it decreases.

We have examined the suggestion that an M0 transition occurs between the 2819.6-keV $0^{\mathrm{-}}$ level of ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}$ and the $0^{+}$ ground state by internal-conversion electron emission. Gamma rays, internal-conversion electrons, and internal ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ pairs were detected from the ${\mathrm{\beta }}^{+}$ and electron capture decay of two-day ${}_{}{}^{170}{}_{}{}^{}\mathrm{Lu}$ ($0^{+}$). At an upper limit of 2×${10}^{\mathrm{-}8}$ electron per ${}_{}{}^{170}{}_{}{}^{}\mathrm{Lu}$ decay, no evidence was obtained for M0 decay of the 2819.6-keV level of ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}$ by single-electron emission.

Using the theoretical α-cluster wave functions, α-spectroscopic factors for the members of the parity doublet ${\mathit{K}}^{\mathrm{\pi }}$=$0^{+}$ and $0^{\mathrm{-}}$bands in ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ have been deduced by the finite-range distorted wave Born approximation analyses of the ${(}^6$Li,d) reaction on ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. Form factors for ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ were calculated with a local potential model which describes α-elastic scattering from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and the resonating group method, respectively. The resulting spectroscopic factors for α-cluster states in ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ are greater than 0.1, which supports an α-cluster model for ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$.

A folding potential for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C scattering is constructed based on the α-particle model of the nucleus using a free α-α interaction. This potential gives a good description of the data in the energy region of 70–160 MeV. This report reveals a sort of nuclear system in which the ‘‘elementary particle’’ behaves as a free one and thus folding models can be tested more ‘‘cleanly.’’

The surface-friction and the extra-push models have been widely used to predict fusion barriers of very heavy ions. Despite their profound differences it has not been possible to establish which model gives a better description of the fusion process. In this work we show that consideration of thermal effects allows for a distinction between the two models. Comparison to experimental data seems to favor the extra-push model.

We calculate the real part of the two-neutron-removal polarization potential for the case of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$${+}^{208}$Pb collisions at energies near and below the Coulomb barrier. The real part of ${\mathit{V}}^{\mathrm{pol}}$ is shown to be predominantly repulsive and to reduce the fusion cross section at above barrier energies. Below the barrier this potential changes sign and thus enhances the fusion cross section. However, this effect is considerably weaker than the hindrance produced by the imaginary part of this potential.