A formalism for the calculation of intermediate energy charge exchange reactions exciting the Δ resonance region in nuclei is presented. The nuclear structure part of the formalism is based on the isobar-hole model and the nuclear reaction part is treated within the distorted-wave impulse approximation (DWIA). In the nuclear structure part, all important nuclear medium effects are included, such as nucleon and isobar binding, two-body Δ isobar-nucleon hole correlations, and intermediate coupling to multiparticle-multihole channels. The latter coupling is treated phenomenologically through a Δ spreading potential. Explicit account is also taken of the nucleon knockout mode and the related nucleon particle-nucleon hole correlations. In order to perform the calculations, we first set up coupled-channel equations for the excited nucleon and Δ, which are slightly, but importantly, transformed into equations for localized functions only. We solve these equations by using the Lanczos method. The resultant formalism allows us to calculate cross sections for Δ excitation, quasielastic scattering, and low-lying Gamow-Teller excitations on the same footing. In this way a detailed study of the nuclear medium effects on the Δ isobar can be done. Particular attention is paid to the Δ-hole correlations in the spin-longitudinal (S⋅qT) channel. It is shown that the coherent pion production events in the exclusive ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(p,n${\mathrm{\pi }}^{+}$${)}^{12}$C(g.s.) and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${(}^3$He,t${\mathrm{\pi }}^{+}$${)}^{12}$C(g.s.) reactions provide a unique signature on the nuclear pionic mode.

We show that the dynamical evolution of density waves in an expanding nuclear system differs markedly from their evolution in an expanded but static system. This leads, in particular, to the growth of instabilities in the stable region of the nuclear matter phase diagram.

We show that it is possible to extract the critical exponents from small percolation lattices. The possibility of performing a similar analysis on data from exclusive nuclear fragmentation experiments is explored.

Three-nucleon transfer by the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$(α,p${)}^{10}$Be reaction at 65 MeV has been carried out with good resolution. A cluster model is compared to the data with the aid of zero-range distorted wave Born approximation reaction calculations, finding consistent spectroscopic factors for low-lying K=$0^{+}$ and $1^{\mathrm{-}}$ bands. Large cluster spectroscopic factors are found for the states at 17.74 and 18.54 MeV that serve as resonances for reactions between ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ at low energies of astrophysical importance. A research for states very near threshold found no transitions that significantly alter the important astrophysical reaction rate.

A liquid hydrogen target was used to study the nuclear fragmentation of beams of relativistic heavy ions, ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ to ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, over an energy range 400 to 900 MeV/nucleon. The experiments were carried out at the Lawrence Berkeley Laboratory Bevalac HISS facility, using the charge-velocity-rigidity method to identify the charged fragments. Here we describe the general concept of the experiment and present total charge-changing cross sections obtained from 17 separate runs. These new measured cross sections display an energy dependence which follows semiempirical model predictions. The mass dependence of the cross sections behaves as predicted by optical models, but within the experimental energy range, the optical model parameters display a clear energy dependence. The isospin of the projectile nuclei also appears to be an important factor in the interaction process.

Recently, highly relativistic Au beams have become available at the Brookhaven National Laboratory, Alternating Gradient Synchrotron. Inclusive production cross sections for composite particles, d, t, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, in 11.5A GeV/c Au+Pt collisions have been measured using a beam line spectrometer. For comparison, composite particle production was also measured in Si+Pt and p+Pt collisions at similar beam momenta per nucleon (14.6A GeV/c and 12.9 GeV/c, respectively). The projectile dependence of the production cross section for each composite particle has been fitted to ${\mathit{A}}_{\mathrm{proj}}^{\mathrm{\alpha }}$. The parameter α can be described by a single function of the mass number and the momentum per nucleon of the produced particle. Additionally, the data are well described by momentum-space coalescence. Comparisons with similar analysis of Bevalac A+A data are made. The coalescence radii extracted from momentum-space coalescence fits are used to determine reaction volumes (‘‘source size’’) within the context of the Sato-Yazaki model.

An increase of the scaled factorial moments with decreasing bin size of phase space—the phenomenon popularly known as intermittency—is a common feature in multiparticle production in relativistic high energy interactions. The data of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + Ag/Br interactions at 2.1 GeV/nucleon also revealed the same feature which, usually, is identified as the revelation of singularity structure of correlation functions. In this article, we extend our analysis of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + Ag/Br interactions at 2.1 GeV/nucleon data in terms of other tools (giving correlations) such as the scaled factorial correlators, the factorial cumulant moments, and the split-bin correlation functions. The study reveals that the information on correlations of our particle production data are contained in two-particle dynamical correlations only and that the two-particle dynamical correlations are due to a resonancelike production mechanism.

A formula for the two-pion correlation function is derived for a chaotic source when the emission spectrum from each space-time point is known It is shown that without fully understanding the evolution process of the source, no realistic source size can be obtained. The differences among different formulas of pion interferometry are also given.

The nuclear excitation is expressed in terms of an intrinsic temperature. When the temperature is raised beyond a certain limiting value the nucleus becomes unstable due to the Coulomb repulsion and falls apart before the critical temperature of the liquid-vapor phase transition is reached. We isolate the finite nucleus from the surrounding vapor by using a subtracted level occupation probability. Thermo- static and limiting properties are calculated in a relativistic Thomas-Fermi approach using density-dependent coupling constants, adjusted to the outcome of relativistic Brueckner-Hartree-Fock nuclear matter treatments, and, for the purpose of comparison, density-independent coupling constants. The disappearance of fusion-like processes in heavy-ion collisions is related to the limiting excitation energy.

The √s and A dependence of ultrarelativistic pA collisions for energies corresponding to future collider experiments at RHIC and LHC is studied with focus on medium effects that affect the parton evolution in nuclear matter. Within the parton cascade model the saturation of the parton densities due to unitarity conservation, the self-contained balance of parton emission and fusion processes, and the mechanism of dynamical screening of long range interactions are analyzed. The resulting inclusive spectra and properties of secondary hadrons are discussed in order to extract aspects of ‘‘QCD in medium’’ from collider experiments.

To analyze the high energy heavy ion reactions performed at Lawrence Berkeley BEVALAC, Brookhaven AGS, and CERN SPS we present a dynamical model that is entirely Poincaré covariant. The description of strong interactions by Lorentz-scalar quasipotentials makes possible a relativistic extension of the cascade concept without losing its inherent simplicity. No field degrees of freedom appear explicitly, neither in elastic nucleon scattering nor in particle creation processes. Although various formalisms describe directly interacting relativistic particles with identical solutions for the two-particle case, they all suffer from different problems in many-particle systems. The basis of our approach is a Hamiltonian formulation for N pointlike nucleons, moving unconstrained in an 8N-dimensional phase space. One additional Lorentz scalar is introduced for an appropriate parametrization of all trajectories, defining also the connection to the proper times of the individual interacting nucleons. The creation of particles, for which Hamiltonian dynamics does not provide a generic mechanism, is incorporated phenomenologically as a ‘‘perturbative’’ process. We describe heavy ion collisions as a sequence of two-particle reactions without any additional fit to experimental data. Pion yield and mass spectra of the heavy fragments agree reasonably well with BEVALAC results. We do not compare to experimental high energy data because the employed mechanism of particle production is certainly improper in that regime. However, the numerical results give an impression on how the reaction evolves.

We present a Poincaré covariant model for ultrarelativistic particle reactions without any field degrees of freedom. A relativistic two-particle interaction is made possible by an enlargement of phase space and a distinction between physical and canonical particle coordinates. A Hamiltonian formalism with a mass-like quasipotential defines the dynamics of the system. Then interaction at a distance causes a change of effective particle masses instead of energy. Particle production is incorporated by a phenomenological decay procedure for the constituents (partons) in a manner analogous to a string fragmentation mechanism. This pure particle picture for Poincaré covariant collision dynamics (PCD model) is compared to other microscopic models and tested by simulations of ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ jet events. Before application to more complex scenarios like ultrarelativistic heavy ion collisions, hard gluonic effects should be included. In the PCD model, this can be done by introduction of massive gluons as particles.

Quasielastic wide-angle ep scattering on the deuteron, the simplest reaction where color transparency can be investigated, is analyzed on the basis of multiple scattering theory. Color transparency reveals itself as a cancellation of elastic and inelastic shadowing. We calculate the energy dependence of the color transparency factor and the effects related to the Fermi motion. Extension of the results on other nuclei is also discussed.

The 1/${\mathit{N}}_{\mathit{c}}$ expansion is developed for the Nambu–Jona-Lasinio model, a commonly used low-energy model of QCD. The next to leading order in this expansion that represents pion and sigma meson exchange in the gap equation is evaluated perturbatively. These contributions are seen to be differing in sign, a feature that is due to their opposite parities. Physically one can interpret this meson exchange as giving rise to screening (π) or antiscreening (σ) of the bare four-point interaction. As a consequence of the higher isospin degeneracy of the pion, the contributions from it are found to dominate. In total, we find that the resulting corrections to the usual Hartree approximation are of the order of 10%, justifying a posteriori the perturbative approach.

We have searched for evidence of the emission of a 17 keV neutrino in the internal bremsstrahlung (IB) spectrum accompanying the electron capture decay of ${}_{}{}^{125}{}_{}{}^{}\mathrm{I}$. The IB spectrum, recorded in a planar Ge detector, has 1.2×${10}^6$ counts per keV at 17 keV below the 2p end point. We set an upper limit of 0.4% for the admixture of a 17 keV neutrino, at the 90% confidence level, and exclude a 0.8% admixture at the 99.6% confidence level. The ${\mathit{Q}}_{\mathrm{EC}}$ value is found to be 185.77±0.06 keV. We also find that the recent calculations of Surić et al., which employ relativistic self-consistent-field atomic wave functions, reproduce the shape and relative intensity of IB partial spectra within a few percent.

Recent results in parity non-conserving neutron-nucleus scattering show a tendency for the parity non-conserving effects to predominantly have the same sign. Explanations of this phenomenon all require a weak matrix element between single-particle levels in heavy nuclei to be ∼100 eV. This paper contains a discussion of this effect and how the same phenomenon will manifest itself in other systems. The gamma decay of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$ is given as an example of a system where the weak matrix element between single-particle levels in a heavy nucleus can be measured directly.

Measurements of differential cross sections at 0° for projectilelike fragments from ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ projectiles at E/A=80 MeV are presented and are compared with the predictions of the abrasion-ablation model, the internuclear cascade model, a high-energy empirical parametrization, and a simple cluster breakup model. The data for both projectiles are in good agreement with the high-energy systematics. The abrasion-ablation and internuclear cascade models can adequately describe the cross sections of fragments from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ with large mass losses, whereas the cluster breakup model can describe the relative cross sections of few-nucleon removal products from both projectiles.

Magnetic substate populations for the $2^{+}$ state at 4.44 MeV in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ were measured in resonant ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{16}$O inelastic scattering by the γ-ray recoil method. The m-substate population has been determined in the coordinate frame where a quantization axis is taken along the center of mass scattering angle of a reaction product. This coordinate frame gives an advantage that a resonance spin J can be obtained directly from m-substate angular distributions compared with the beam-axis frame. In addition a decay L value is sensitive to the relative intensity between each m-substate cross section. Our data suggest a spin assignment of ${\mathit{J}}^{\mathrm{\pi }}$=${16}^{+}$ or ${17}^{\mathrm{-}}$ for the structures at ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=29.8 MeV and 31.8 MeV. Both structures are determined to decay dominantly through the aligned configuration of L=J-2.

High spin states of ${}_{}{}^{84}{}_{}{}^{}\mathrm{Sr}$ nucleus excited through the ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$${(}^{36}$S,2p2n) reaction at 130 MeV energy were studied utilizing the Oak Ridge Compton-Suppression Spectrometer System. The level scheme has been extended up to probably ${\mathit{I}}^{\mathrm{\pi }}$=(${24}^{+}$) at 15 084 keV excitation energy for the positive parity band. The moment of inertia, for angular frequency higher than 0.58 MeV, presented an almost constant value.

${}_{}{}^{108}{}_{}{}^{}\mathrm{I}$ is confirmed as a predominant alpha particle emitter with an energy of 3947±5 keV and half-life of 36±6 ms. The first observation of alpha decays of ${}_{}{}^{106}{}_{}{}^{}\mathrm{Te}$ nuclei produced directly as evaporation residues is reported with a measured energy of 4128±9 keV and a half-life of ${60}_{\mathrm{-}20}^{+40\mathrm{}}$ μs. Alpha decay branching ratios for ${}_{}{}^{112}{}_{}{}^{}\mathrm{Xe}$ and ${}_{}{}^{108}{}_{}{}^{}\mathrm{Te}$ have been measured from correlations with preceding proton decays as 0.$8_{\mathrm{-}0.5}^{+1.1\mathrm{}}$% and 49±4%, respectively. Improved measurements for the ${}_{}{}^{112}{}_{}{}^{}\mathrm{Xe}$ alpha decay energy of 3216±7 keV and the half-life of ${}_{}{}^{107}{}_{}{}^{}\mathrm{Te}$ of 3.1±0.1 ms are also reported.