Within a hadronic transport model we study in detail contributions to kaon yields and momentum spectra from various baryon (resonance)-baryon (resonance) and πN interactions in heavy-ion collisions at beam energies near the free-space kaon production threshold. It is found that the finite lifetime of baryon resonances affects significantly the shape of kaon spectra, and the high energy parts of the kaon spectra are dominated by kaons from πN→Λ${\mathit{K}}^{+}$ processes. ${\mathit{N}}^{\mathrm{*}}$(1440) resonances are found to contribute about 10% to the kaon yield. Effects of boosting the Fermi momentum distributions of the two colliding nuclei into their center-of-mass frame, centrality of the reaction, as well as the nuclear equation of state on kaon yields, and spectra are also discussed. Model calculations on the ${\mathit{K}}^{+}$ spectra for the reaction of Au+Au at ${\mathit{E}}_{\mathrm{beam}}$/A=1.0 GeV are compared with the experimental data from the KaoS Collaboration.

We describe a simple model developed to study the production and annihilation of antiprotons in nucleus-nucleus collisions. The model can be used to calculate the antiproton yields as functions of global observables such as multiplicity, transverse energy, and zero degree energy. We discuss the predictions of the model, and its relevance to the antiproton measurements at the Brookhaven National Laboratory Alternating Gradient Synchrotron facility.

Signatures of collective effects are studied in the quark gluon string model and in the fluid dynamical model for Au+Au collisions at 11.6A GeV/c. In the fluid dynamical model the dependence of observables on the quark-gluon plasma (QGP) formation in the equation of state is pointed out although the maximal total amount of pure QGP formed is only about 8 ${\mathrm{fm}}^3$ in these reactions. In contrast to the baryon rapidity distribution, the in-plane transverse flow and especially the squeeze-out effect are particularly sensitive to the EOS. In the QGSM the lifetime and extent of baryon density in strings are studied. The QGSM picture is very similar to the one obtained in the fluid dynamical model with a pure hadronic EOS.

The properties of pions from the hot and dense reaction stage of relativistic heavy ion collisions are investigated with the Quantum Molecular Dynamics model. Pions originating from this reaction stage stem from resonance decay with enhanced mass. They carry high transverse moments. The calculation shows a direct correlation between high ${\mathit{p}}_{\mathit{t}}$ pions, early freeze-out times, and high freeze-out densities. A measurement of the mass distributions of p-π correlations (e.g., the ${\mathrm{\Delta }}^{++}$) in different ${\mathit{p}}_{\mathit{t}}$ bins is proposed to distinguish different reaction stages.

Meson-exchange current (MEC) contributions to the parity-violating (PV) asymmetry for elastic scattering of polarized electrons from ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are calculated over a range of momentum transfer using Monte Carlo methods and a variational ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ ground state wave function. The results indicate that MEC’s generate a negligible contribution to the asymmetry at low ‖q‖, where a determination of the nucleon’s mean square strangeness radius could be carried out at CEBAF. At larger values of momentum transfer—beyond the first diffraction minimum—two-body corrections from the ρ-π ‘‘strangeness charge’’ operator enter the asymmetry at a potentially observable level, even in the limit of vanishing strange-quark matrix elements of the nucleon. For purposes of constraining the nucleon’s strangeness electric form factor, theoretical uncertainties associated with these MEC contributions do not appear to impose serious limitations.

The problems and uncertainties in the search for color transparency at intermediate ${\mathrm{Q}}^2$ are considered. We show that conventional (optical) model [distorted wave impulse approximation (DWIA)] predicts a substantial change of the transparency, T, with ${\mathrm{Q}}^2$ in the kinematics of the NE-18 (e,e′p) experiment, while the color transparency phenomenon may lead to nearly ${\mathrm{Q}}^2$ independent T. In the case of A(p,2p) reaction we demonstrate that the conventional optical model well describes the 1 GeV A(p,2p) data but not the transparency observed at higher energies. We find also that DWIA (with or without color transparency) predicts strong dependence of T on the momentum of the struck nucleon which is consistent with the pattern of the Brookhaven National Laboratory A(p,2p) data at ${\mathrm{p}}_{\mathrm{N}}$=6 GeV/c and 10 GeV/c.

The depopulation of ${}_{}{}^{180}{}_{}{}^{}\mathrm{Ta}_{}^{\mathit{m}}{}_{}{}^{}$ by Coulomb excitation was investigated in a thick-target experiment using beams of ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ and ${}_{}{}^{36}{}_{}{}^{}\mathrm{S}$ with energies of 70–130 MeV on disks of natural tantalum. The resulting ${}_{}{}^{180}{}_{}{}^{}\mathrm{Ta}$ ground-state population was measured by detecting its eight-hour decay. At the higher incident energies the observed ${}_{}{}^{180}{}_{}{}^{}\mathrm{Ta}$ yield is dominated by sub-Coulomb neutron pickup transfer reactions on the ${10}^4$ times more abundant ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$. At the lower incident energies in ${}_{}{}^{180}{}_{}{}^{}\mathrm{Ta}$ ground-state yield is found to be compatible with Coulomb excitation of the isomer to an intermediate level with energies ${\mathit{E}}_{\mathit{x}}$<1 MeV and a reduced transition probability B(E2)≃0.02–0.25 Weisskopf units. Consequences for the astrophysical production mechanism of ${}_{}{}^{180}{}_{}{}^{}\mathrm{Ta}$ are discussed.

The absolute cross section of the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(α,γ${)}^7$Li reaction has been measured for 50≤${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$≤1200 keV. Specially prepared ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ targets were bombarded with an ${\mathrm{\alpha }}^{+}$ beam, and γ rays were detected using an 85% high-purity germanium detector. Total S factors and the branching ratios for radiative capture to the two final bound states are reported for the entire energy range. Angular distributions of the capture γ rays were measured for nine energies in the range 115≤${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$≤1200 keV. Legendre coefficients extracted from fits to the angular distributions are also reported. The energy dependence of the measured S factors is found to be in agreement with existing theoretical calculations. The new results are used to calculate the thermonuclear reaction rate for temperatures below 10 GK, required for computing the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ abundance in primordial nucleosynthesis.

Nine new very neutron-deficient isotopes of Ag, Pd, Rh, and Ru have been identified among the reaction products of an E/A=60 MeV ${}_{}{}^{106}{}_{}{}^{}\mathrm{Cd}$ beam using the A1200 projectile fragment separator at the National Superconducting Cyclotron Laboratory. One of these isotopes, ${}_{}{}^{94}{}_{}{}^{}\mathrm{Ag}$, is among the heaviest N=Z nuclei observed so far. The resulting mass spectra are presented and the astrophysical implications of the stability towards proton emission of one of the new isotopes, ${}_{}{}^{95}{}_{}{}^{}\mathrm{Ag}$, are discussed.

The width of 3841-keV level in ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ was precisely measured in nuclear resonance fluorescence experiments performed at the Stuttgart Dynamitron facility. The result of Γ(3841 keV)=(92±6) meV is compared with upper limits quoted in the literature. Possible particle-hole configurations of the 3841-keV level are discussed.

In this paper we present a model for three nucleon pion absorption based on the assumption that pion absorption on three nucleons is a one-step process. In the assumption that the square of the effective matrix element is proportional to the probability that three nucleons are contained inside a certain volume V, this model is equal to the Fermi statistical model. The construction of the volume V is different from the Fermi model. Very good agreement between this simple model and experimental data for the energy dependence of the three-nucleon pion absorption cross section on ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ opens a new possibility for the explanation of multinucleon effects in pion absorption.

The asymptotic normalization constants (ANC) ${\mathit{C}}_0$ and ${\mathit{C}}_2$ of the triton have been calculated by the hyperspherical harmonics expansion method with the Reid soft core potential (no three body force). The results do not agree with the corresponding calculations by the Faddeev method, when only a few hyperspherical partial waves are included. However Schneider’s convergence theorems on hyperspherical expansion allow one to extrapolate the results for a large number of partial waves and then they agree fairly well with the Faddeev results. This indicates that even though the hyperspherical expansion for the asymptotic wave function is very slow, a convergent and reliable wave function is attained by extrapolation of a relatively small-sized calculation.

We calculate an electrical chemical potential, ${\mathrm{\mu }}_{\mathit{e}}$, for hadronic matter produced in relativistic collisions of nuclei with (extremely) large atomic numbers. We find ${\mathrm{\mu }}_{\mathit{e}}$<0 which leads to an asymmetry in the pion production (${\mathrm{\pi }}^{\mathrm{-}}$/${\mathrm{\pi }}^{+}$>1) and a difference between positive and negative pion spectra at low transverse momenta.

In tests exploiting the unique sensitivity of a fully chaotic system like the compound nucleus, the possibility exists that unknown resonance parameters and interaction matrix elements taken on values which preclude the observation of a violation of time-reversal invariance independent of the strength of the time-reversal noninvariant interaction. A nontrivial constraint on time-reversal tests is implied, namely, that the observable has to be sampled a minimum number of times ${\mathit{M}}_{\min }$ where ${\mathit{M}}_{\min }$>3. Several experiments purporting to be tests of time reversal do not satisfy this condition.

The concept of the multichannel dynamical symmetry is introduced. This symmetry may show up in an atomic nucleus due to its different cluster configurations, and connects the interactions of distinct reaction channels. The correlated distribution of different cluster states at low and high energies can serve as a signature of it. An application of the ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ nucelus is performed in terms of the ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$+α and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{16}$O fragmentations.

It is found that the E1 contribution to the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(α,γ${)}^{16}$O cross section at the low energies of interest in astrophysics is poorly determined by K-matrix fits to the available data when the background term contains $1^{\mathrm{-}}$ subthreshold echo pole.

Deuteron properties have been calculated in the framework of the constituent quark model using a quark-quark interaction which incorporates σ and π chiral mesons besides the one-gluon exchange between quarks. This interaction is able to describe simultaneously the nucleon-nucleon phase shifts. In contrast with earlier calculations, in which equivalent meson potentials between nucleons have been used, this description includes only interactions between quarks.

We determined the electric form factor ${\mathit{G}}_{\mathit{E}}^{\mathit{n}}$ of the neutron from the quasielastic ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(e→,${\mathit{e}}^{\mathcal{’}}$n→${)}^1$H reaction at a central squared four-momentum transfer ${\mathit{Q}}^2$=0.255 (GeV/c${)}^2$ with a longitudinally polarized electron beam of 868 MeV and a low (∼0.8%) duty factor. A neutron polarimeter designed and constructed specifically for this experiment was used to measure the sideways polarization of the recoil neutron, which was detected in coincidence with the scattered electron. Theoretical calculations have established that this polarization-transfer technique for quasielastic scattering produces a value of ${\mathit{G}}_{\mathit{E}}^{\mathit{n}}$ that shows little sensitivity to the influence of final-state interactions, meson-exchange currents, isobar configurations, and deuteron structure. The value for ${\mathit{G}}_{\mathit{E}}^{\mathit{n}}$ from this measurement is 0.066±0.036±0.009.

The low-lying level structure of the neutron-deficient isotope ${}_{}{}^{202}{}_{}{}^{}\mathrm{Rn}$ has been studied for the first time, using the ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$${(}^{27}$Al,6n) and ${}_{}{}^{192}{}_{}{}^{}\mathrm{Pt}$${(}^{16}$O,6n) reactions. Gamma-ray transitions between excited states in ${}_{}{}^{202}{}_{}{}^{}\mathrm{Rn}$ were identified by mass tagging using a recoil mass separator, the Argonne Fragment Mass Analyzer, and by observation of coincident x rays. Transitions in ${}_{}{}^{203}{}_{}{}^{}\mathrm{Rn}$ were also identified. The level scheme deduced from these data is consistent with the systematics of light radon isotopes below the N=126 shell closure and with theoretical calculations indicating that the ground-state shape should not be strongly deformed at N=116.