The E-802 Collaboration at the BNL-AGS has measured charged particle multiplicity distributions from central (ZCAL) collisions of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Cu at 14.6A GeV/c as a function of the pseudorapidity interval δη≥0.1 in the range 1.2≤η≤2.2. The fluctuations of these distributions as a function of the pseudorapidity interval have been studied by the method of normalized factorial moments and also by directly fitting the measurements to negative binomial distributions (NBD). Excellent fits to NBD were obtained in all δη bins, allowing, for the first time, a systematic formulation of the subject of intermittency in terms of distributions to complement the description based on normalized factorial moments. In agreement with all previous measurements of NBD fits to multiplicity distributions in hadron and lepton reactions, the k parameter of the NBD fit for central ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Cu collisions is found to exhibit an apparently linear increase with the δη interval, albeit with a much steeper slope than for other reactions, and a nonzero intercept, k(0)≠0. The evolution of the NBD parameter k(δη) is used to determine the two-particle short-range rapidity correlation length for central ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Cu collisions, ξ=0.18±0.05, which is much shorter than the value ξ∼1–3 for hadron collisions, but this is a quantitative rather than a qualitative difference. These results lead to a simple and elegant explanation of the intermittency formalism, without resort to fractals, for all reactions, which demystifies intermittency—for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+Cu central collisions, intermittency is nothing more than the apparent statistical independence of the multiplicity in small pseudorapidity bins, δη∼0.2, due to the surprisingly short two-particle rapidity correlation length.

We have conducted a search for bound states of a negative pion and a number of neutrons (pineuts) using the E814 spectrometer. A beam of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ at a momentum of 14.6A GeV/c was used to bombard targets of Al, Cu, Sn, and Pb. We describe our experimental technique, present measured upper limits for pineut production, and discuss the significance of our results.

Rapidity distributions of baryons from nucleus-nucleus, $p$-nucleus, and $p-p$ interactions at 11.6, 14.6, and 200 GeV/c per nucleon incident momenta are reviewed. Average rapidity losses relative to the beam rapidity are derived in a consistent way and the systematics are described and discussed. The baryon multiplicities in the midrapidity region relative to simple geometrical sum rules are determined and the systematics of the opacity of the collisions are described. The main conclusions are that the average rapidity losses in central nucleus-nucleus collisions scale with the projectile rapidity and that the opacity of central collisions depends strongly on the size of the collision system and weakly on incident momentum.

Using a quadratic saddle-point approximation we show how information about a particle-emitting source can be extracted from Gaussian fits to two-particle correlation data. Although the formalism is completely general, extraction of the relevant parameters is much simpler for sources within an interesting class of azimuthally symmetric models. After discussing the standard fitting procedure we introduce a new Gaussian fitting procedure which is an azimuthally symmetric generalization of the Yano-Koonin formalism for spherically symmetric sources. This new fitting procedure has the advantage that in addition to being able to measure source parameters in a fixed frame or the longitudinally comoving system, it can also measure these parameters in the local rest frame of the source.

Dilepton production is considered within a complete dynamical framework for thermalized matter assumed to be formed in ultrarelativistic heavy-ion collisions. Our model includes (i) chemical equilibration processes in the initially gluon enriched plasma, (ii) longitudinal as well as transverse expansion, and (iii) the hadronization through a mixed phase. Besides the basic electromagnetic quark–antiquark annihilation process we also take into account the QCD Compton-like and annihilation processes for calculating the dilepton rate in the deconfined phase, while in the hadronic stage we employ a parametrization of the effective form factor which is based on the complete set of meson decays and reactions. We find that, due to the transverse expansion of the matter, the dilepton yield from the hadron gas is strongly reduced and, therefore, the deconfined matter gives the dominant contribution in case of initial conditions which are expected to be achieved at RHIC. This provides the basis for the ${\mathit{M}}_{\mathrm{\perp }}$ scaling restoration of the dilepton spectra from thermalized matter.

Transport models have successfully described many aspects of intermediate energy heavy-ion collision dynamics. As the energies increase in these models to the ultrarelativistic regime, Lorentz covariance and causality are not strictly respected. The standard argument is that such effects are not important to final results; but they have not been seriously considered at high energies. We point out how and why these happen, how serious of a problem they may be and suggest ways of reducing or eliminating the undesirable effects.

We estimate the probability that a hard nucleon-nucleon collision is able to nucleate a seed of quark-gluon plasma in the surrounding hot and dense hadronic matter formed during a central collision of two large nuclei at AGS energies. The probability of producing at least one such seed is on the order of 1–100 %. We investigate the influence of quark-gluon plasma formation on the observed multiplicity distribution and find that it may lead to noticeable structure in the form of a bump or shoulder.

The nucleon is formulated as a relativistic system of three constituent quarks interacting via a zero-range two-body force in the null plane. The covariance of the null-plane Faddeev-like equation under kinematical front-form boosts is discussed. The nucleon wave function is obtained from the numerical solution of the Faddeev equation in the null plane. The proton electric form factor, obtained from the Faddeev wave function, reproduces the experimental data for low momentum transfers and qualitatively describes the asymptotic region.

We study nucleon structure in the relativistic quark model based on the Bakamjian-Thomas construction of the Poincaré generators for an arbitrary quantization surface. The one body, single particle approximation to the current operators is used to calculate electromagnetic matrix elements. The Lorentz symmetry breaking resulting from such an approximation is fully investigated. The results for the light front and instant quantization limits are detailed. A suggestion for the resolution of the quark model inability to simultaneously describe the positive neutron electric form factor, ${\mathit{G}}_{\mathit{E}}^{\mathit{n}}$(${\mathit{Q}}^2$) at small ${\mathit{Q}}^2$ and the negative slope of the neutron to proton structure function ratio at large x is presented.

Using the Schwinger-Keldysh formalism we develop a method for solving self-consistently the Schwinger-Dyson equations for pions and deltas in nuclear medium at nonzero temperature. The vertex corrections are neglected and the nucleon is treated as a mean field. The correct analytic properties of the pion’s and delta’s propagators are assured by using dispersion relations to relate their real and imaginary parts. While the width of the pion’s spectral function at low momentum increases with increasing temperature, the opposite is true for higher momenta implying that the quasiparticle approximation is a rather good one at high temperature.

The neutron capture cross sections of ${}_{}{}^{152}{}_{}{}^{}\mathrm{Gd}$, ${}_{}{}^{154}{}_{}{}^{}\mathrm{Gd}$, ${}_{}{}^{155}{}_{}{}^{}\mathrm{Gd}$, ${}_{}{}^{156}{}_{}{}^{}\mathrm{Gd}$, ${}_{}{}^{157}{}_{}{}^{}\mathrm{Gd}$, and ${}_{}{}^{158}{}_{}{}^{}\mathrm{Gd}$ were measured in the energy range from 3 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$(p,n${)}^7$Be reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 4π Barium Fluoride Detector, which was improved by replacing crystals with high α background and by introducing a pierced crystal at zero degrees with respect to the beam axis. These changes resulted in a significantly increased efficiency for capture events. The main experimental problem was that the samples of the two s isotopes ${}_{}{}^{152}{}_{}{}^{}\mathrm{Gd}$ and ${}_{}{}^{154}{}_{}{}^{}\mathrm{Gd}$ showed only relatively low enrichment. Nevertheless, the spectroscopic quality of the ${\mathrm{BaF}}_2$ detector allowed evaluation of the corresponding corrections for isotopic impurities reliably. The cross section ratios could be determined with an overall uncertainty of typically 1%, an improvement by factors of five to ten compared to existing data. Severe discrepancies were found with respect to previous results. Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT=10 keV and 100 keV. The new stellar cross sections were used for an updated analysis of the s-process reaction flow in the mass region between samarium and gadolinium, which is characterized by branchings at ${}_{}{}^{151}{}_{}{}^{}\mathrm{Sm}$, ${}_{}{}^{154}{}_{}{}^{}\mathrm{Eu}$, and ${}_{}{}^{155}{}_{}{}^{}\mathrm{Eu}$. With the classical approach, the s-process temperature could be constrained corresponding to a range of thermal energies between kT=28 and 33 keV. The ${}_{}{}^{152}{}_{}{}^{}\mathrm{Gd}$ production in low mass stars was found to depend strongly on the neutron freeze-out at the end of the helium shell burning episodes.

The absolute intensity of the internal bremsstrahlung spectrum accompanying the electron capture decay of ${}_{}{}^{125}{}_{}{}^{}\mathrm{I}$ has been measured and compared to the recent calculation of Surić et al. The measured intensity above the 1s end point is found to be (86±10)% of the calculated intensity.

Two-proton correlation functions are measured for inclusive collisions of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ at E/A=200 MeV. Calculations with the Boltzmann-Uehling-Uhlenbeck transport theory overpredict the dependence of the correlation function on the total momentum of the coincident proton pair, but correctly reproduce the energy-integrated correlation function.

A new calculation of the binding energy of nuclear matter in the Brueckner-Hartree-Fock approximation with the Paris potential using the standard and continuous choices of single particle energies is presented, paying special attention to the numerical accuracy and higher partial waves. Comparison with other calculations is made and the accuracy of the state of the art for the Brueckner-Hartree-Fock method is assessed.

We emphasize that the composite structure of the nucleon may play quite an important role in nuclear physics. It is shown that the momentum-dependent repulsive force of second order in the scalar field, which plays an important role in Dirac phenomenology, can be found in the quark-meson coupling (QMC) model, and that the properties of nuclear matter are well described through the quark-scalar density in a nucleon and a self-consistency condition for the scalar field. The difference between theories of pointlike nucleons and composite ones may be seen in the change of the ω-meson mass in nuclear matter if the composite nature of the nucleon suppresses contributions from nucleon-antinucleon pair creation.

The multiphonon structure is shown for the ${\mathrm{SO}}_6$ limit of the Ginocchio model. We can see that the multiphonon description is valid strictly in this fermion system. The phonon states are created by the quadrupole operator ${\mathit{P}}^2$ with proper symmetrization. All the σ=N states can be described in this scheme in terms of phonon quanta and two-phonon anharmonicity. The dipole and octupole interactions are also included in the Hamiltonian for both the boson and fermion systems.

Spin-transfer observables have been calculated for the quasielastic (p→,n→) reaction according to the relativistic plane wave impulse approximation, using two different parametrizations of the NN interaction. The target nucleus is ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and the proton lab energies range from 135 to 500 MeV, while the momentum transfer is kept fixed at a (fairly large) value of 1.97 ${\mathrm{fm}}^{\mathrm{-}1}$. An analysis is made of the sensitivity of these spin observables with respect to relativistic Dirac effects, the form of the πN vertex and exchange contributions to the NN amplitudes. These sensitivities are found to be selective with respect to the different spin observables over the whole proton energy range. The results are also compared to those of the corresponding (p→,p${\to }^{\prime }$) reaction, which we formerly presented.

We study multiple preequilibrium emission in nucleon induced reactions at intermediate energies, and compare quantum molecular dynamics (QMD) calculations with multistep-direct Feshbach-Kerman-Koonin results [M. B. Chadwick, P. G. Young, D. C. George, and Y. Watanabe, Phys. Rev. C 50, 996 (1994)]. When the theoretical expressions of this reference are reformulated so that the definitions of primary and multiple emission correspond to those used in QMD, the two theories yield similar results for primary and multiple preequilibrium emission. We use QMD as a tool to determine the multiplicities of fast preequilibrium nucleons as a function of incident energy. For fast particle cross sections to exceed 5% of the inclusive preequilibrium emission cross sections we find that two particles should be included in reactions above 50 MeV, three above about 180 MeV, and four are only needed when the incident energy exceeds about 400 MeV.

The local density approximation (LDA) for the exchange potential of QHD-I presented in a previous publication [R. N. Schmid, E. Engel, and R. M. Dreizler, Phys. Rev. C 52, 164 (1995)] is extended to ρ mesons and pions to allow for realistic applications of the density functional approach to quantum hadrodynamics. Some results for spherical nuclei show that the LDA is an accurate approximation to the nonlocal Hartree-Fock–exchange potential also on the level of QHD-II.

In a recent publication Csótó suggests that the sequential decay of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ through resonances in ${}_{}{}^{10}{}_{}{}^{}\mathrm{Li}$ could explain the peak seen at 1.2 MeV of excitation in the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$(${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^{+}$) reaction. We point out that this is in conflict with widely accepted notions of probe and target interactions in the measurement of inclusive excitation functions via nuclear reactions ranging from inelastic scattering and heavy-ion transfer reactions to pion double-charge exchange. We also show that the suggested mechanism leads to incorrect predictions in other nuclei, and so we conclude that the apparent success of the mechanism in explaining the observed energy of excited states in the ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^6{}_{}{}^{}\mathrm{He}$ systems is accidental.