Proton propagation in nuclei was studied using the (e,e’p) reaction in the quasifree region. The coincidence (e,e’p) cross sections were measured at an electron angle of 50.4° and proton angles of 50.1°, 58.2°, 67.9°, and 72.9° for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ targets at a beam energy of 779.5 MeV. The average outgoing proton energy was 180 MeV. The ratio of the (e,e’p) yield to the simultaneously measured (e,e’) yield was compared to that calculated in the plane-wave impulse approximation and an experimental transmission defined. These experimental transmissions are considerably larger (a factor of ∼2 for ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$) than those one would calculate from the free N-N cross sections folded into the nuclear density distribution. A new calculation that includes medium effects (N-N correlations, density dependence of the N-N cross sections and Pauli suppression) accounts for this increase.

A simple relation between the nucleon-nucleon scattering cross sections in vacuum and in nuclear matter is proposed. It consistently takes into account the velocity dependence of the nuclear mean field and Pauli blocking, and is shown to be fairly accurate. It is used to study the mean free path of nucleons in nuclear matter and the imaginary part of the optical potential. It is also used with the local density approximation and the correlated Glauber approximation to calculate the transparency of nuclei as measured by (e,e’p) reactions. The Pauli blocking, velocity dependence of the nuclear mean field, and the ground-state correlations increase the transparency, and all the three effects are necessary to explain the observed transparencies of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ for recoiling 180 MeV protons.

Conditions optimum for the first experimental verification of the multiplication electromagnetic excitations of nuclei in relativistic nucleus-nucleus collisions are described. The relative magnitudes of three important physical processes that might interfere with such a measurement are compared to the predicted strengths for the single and multiple electromagnetic excitations for various choices of the projectile mass and beam energy. Strategies are presented for making inferences concerning the presence of multiple excitation strength in experimental data.

A quasiparticle Hamiltonian, which includes the effects of Hartree-Fock and correlations, has been introduced through a parametrization of the radial shape of the effective mass ${\mathit{m}}^{\mathrm{*}}$(r)/m. Within this phenomenological quasiparticle approach the longitudinal and transverse response functions of quasielastic electron scatterings are studied. It is found that the quasiparticle effective mass plays an important role on the nuclear response functions. The correlations of a nucleon coupling to the nuclear surface excitations have little effects at the momentum transfer q>400 MeV/c. Though this model could improve the agreement with experiments, the discrepancy on the longitudinal response remains to be solved.

We present the rapidity and transverse momentum distributions of protons and neutrons from collisions between 14.6 GeV/nucleon beams of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ and targets of Al, Cu, and Pb. The data were measured in the forward spectrometer/target calorimeter detectors of the E814 apparatus. The results indicate the existence of two distinct domains, one of beam rapidity projectilelike nucleons, and the second of participant nucleons. From the former, the in-medium inelastic nucleon-nucleon cross section is deduced. It is found to agree, within 10%, with the ‘‘free’’ value of 30 mb although under present conditions one of the two colliding nucleons has been struck before with a high probability. We compare with the present data the predictions of a fragmentation model as well as of models dealing explicitly with the heavy-ion collision and particle creation and emission.

Effects associated with the Dirac sea of nucleons have been proposed as important to several nuclear physics problems. The simplest interpretation of these effects is in terms of virtual NN¯ pairs. Here it is argued that the composite nature of the nucleon probably suppresses the contribution of NN¯ pairs compared to what is expected in naive Dirac hole theory. This is made plausible by studying tractable systems of interacting composite fermions. These systems include general topological soliton models in 1+1 dimensions, the exactly solvable massive Thirring model and large-${\mathit{N}}_{\mathit{c}}$ QCD. It is convenient to discuss these models in terms of a compositeness parameter c=MR, where M and R are the mass and intrinsic size of the composite fermion. It is found on general theoretical grounds that for these systems in the limit c→∞ the NN¯ pairs contributions are smaller than any power law in c. The successful Dirac phenomenology of intermediate energy proton-nucleus scattering can be reconciled with this suppression of virtual NN¯. The ‘‘z graphs’’ in the phenomenology, however, should not be interpreted as arising from virtual NN¯ pairs. One-nucleon-loop contributions in quantum hadrodynamics do appear to be suppressed.

Properties of neutron stars derived from the hybrid derivative coupling model of nuclear field theory are studied. Generalized beta equilibrium with all baryon types to convergence is allowed. Hyperon couplings compatible with the inferred binding energy of the lambda hyperon in saturated nuclear matter predict a large hyperon population, with neutrons having a bare majority population in a 1.5${\mathit{M}}_{\mathrm{\odot }}$ neutron star. Among the properties studied are the limits on rotation imposed by gravitation-radiation-reaction instabilities as moderated by viscosity. These instabilities place a lower limit on rotational periods of neutron and hybrid stars of about 1 ms.

With the use of a velocity filter, the α-particle decays of ${}_{}{}^{224}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{225}{}_{}{}^{}\mathrm{U}$ were studied in ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ bombardments of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$. The data obtained for these two isotopes are compared with those of previous investigators, and the α-decay rates of ${}_{}{}^{222,224,226}{}_{}{}^{}\mathrm{U}$ are discussed within the context of partial α half-lives for even-even nuclei with Z≥84.

The total deuteron photodisintegration cross section has been determined in an alternative way, based on the absolute measurement of the 90° cross section and, to a lesser extent, the 0° and 180° cross sections. The accuracy of the deduced total cross sections amounts to 3%, including systematic errors. The agreement of our data with the results from recent theoretical calculations is very good.

The classical approximation for calculating two-proton correlation functions at small relative momenta is evaluated for emission from long-lived sources. For emission times larger than approximately 500 fm/c, the classical approximation is valid. For shorter emission times, antisymmetrization and the strong nuclear interaction become increasingly important. For emission with long lifetimes, distortions in the Coulomb field of heavy reaction residues appear to be of minor importance.

The purity of a neutron-proton symmetry called F spin is estimated in collective nuclei. Two simple formulas are shown to provide a quick and accurate estimate for F spin admixtures in the ground band. Conclusions are also drawn about quadrupole effective charges in collective nuclei.

We investigate a technique to reconstruct spectroscopic sums for the transfer of the even type of nucleon from an odd-even nucleus, given an orbital occupancy in the target and a limited amount of additional information taken from the analog transfer reaction. The technique is applied to ${\mathit{f}}_{7/2}$ neutron transfer on ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}$, and ${\mathit{f}}_{7/2}$ proton transfer on ${}_{}{}^{49}{}_{}{}^{}\mathrm{Ti}$.

Statistical model calculations including nuclear dissipation were performed to calculate the high-energy γ-ray spectrum following the reaction ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{159}$Tb. Including dissipation changes the spin population distribution leading to evaporation residues and fission. The calculations show that a larger fraction of the highest partial waves contributes to evaporation residues than standard statistical model calculations predict (an increase of 65% for spins >65ħ). This effect is shown to provide an explanation for enhanced feeding of superdeformed bands which are populated by the highest partial waves leading to evaporation residues.

Systematic behavior observed in the sub- and near-barrier fusion cross sections recently by Stelson et al. reveals a new threshold phenomenon in sub-barrier fusion reactions. We present evidence that the threshold energy mentioned above is approximately equal to another threshold energy extracted from the imaginary part of the optical potential for elastic scattering in the vicinity of the Coulomb barrier. Implications of this agreement are discussed on the basis of the extended optical model. We then show that the main features of the systematics observed in fusion cross sections can also be understood within the framework of this model.

We show that a parity-nonconserving pion-nucleon coupling, forbidden by Barton theorem for free nucleons, becomes effective for off-mass-shell nucleons bound in the nuclear medium. A new term in the parity-nonconserving nuclear Hamiltonian generated by this coupling is obtained.

The absolute differential cross section and analyzing powers ${\mathit{A}}_{\mathit{y}}$(θ), ${\mathit{A}}_{\mathit{y}\mathit{y}}$(θ), and ${\mathit{T}}_{20}$(θ) of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(d→,γ${)}^5$Li reaction have been measured with an 800 keV deuteron beam which was stopped in a gaseous ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ target. A transition matrix element analysis of the data leads to two solutions, both of which indicate the reaction proceeds predominantly through s-wave (E1) capture, with small admixtures of M1 radiation. One solution has predominantly ${}_{}{}^4{}_{}{}^{}$${\mathit{s}}_{3/2}$(E1) capture strength, the other has nearly equal capture strengths from the ${}_{}{}^2{}_{}{}^{}$${\mathit{s}}_{1/2}$(E1) and ${}_{}{}^4{}_{}{}^{}$${\mathit{s}}_{3/2}$(E1) transition matrix elements. Resonating group model (RGM) calculations have been performed which favor the solution with dominant ${}_{}{}^4{}_{}{}^{}$${\mathit{s}}_{3/2}$(E1) capture strength. In the RGM picture, the ‘‘fusion’’ resonance in the capture cross section is a consequence of the tensor force, which couples the [d${+}^3$He${]}_{\mathit{J}=3/2\mathrm{}}^{\mathit{S}=3/2\mathrm{}}$ scattering channel to the [p${+}^4$He${]}_{\mathit{J}=3/2\mathrm{}}^{\mathit{S}=1/2\mathrm{}}$ scattering channel, enabling the reaction to proceed via the ΔS=0 (E1) transition to the ground state. The finite tensor analyzing powers of the present experiment serve to support this interpretation of the role of the tensor force.

Components of α-particle wave functions corresponding to d-d configurations are used to predict analyzing powers in the (d,α) reaction. Tensor analyzing powers, especially ${\mathit{A}}_{\mathit{x}\mathit{x}}$, are shown to clearly distinguish between wave functions generated by different realistic nucleon-nucleon interactions. Data for the ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$(d,α${)}^{56}$Co reaction to the $7^{+}$ stretched-nucleon-orbital state at 2.283-MeV excitation in ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$, measured with 22-MeV deuterons, are compared to predictions from the Argonne and Urbana interactions. Similar comparisons are made to data for the lowest ${\mathit{J}}^{\mathrm{\pi }}$=$7^{+}$ state in ${}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ populated by the ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$(d,α${)}^{48}$Sc reaction at 16 MeV.

An accurate measurement of the n-p differential cross section, in the angular range 116–180°, at 96 MeV is reported. Between 150° and 180° the angular distribution is steeper than earlier measurements and potential predictions. The sensitivity of the differential cross section to isospin-singlet, J≤4 phase-shift parameters was studied, and it was found that the observed difference at the most backward angles is sensitive mainly to L≥3 phase shifts.

Cross sections from 0° to 10° (lab) have been measured for ground-state Gamow-Teller transitions for the reactions ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(n,p${)}^6$He, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(n,p${)}^{12}$B and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$(n,p${)}^{13}$B from 60 to 260 MeV. The 90-m station at the Weapons Neutron Research facility at Los Alamos National Laboratory was used to obtain these data. Unit cross sections (σ) have been obtained and are compared with existing (n,p) and (p,n) data. The volume integrals (${\mathit{J}}_{\mathrm{\sigma }\mathrm{\tau }}$) for the spin-flip isospin-flip part of the effective nucleon-nucleon interaction have also been obtained and are compared with theoretical predictions.