Elastic cross sections for the scattering of positive and negative pions from ${}_{}{}^{58}{}_{}{}^{}$,60,64Ni were measured at 30 MeV incident pion energy. A clear isotope effect was observed in the ${\pi }^{\mathrm{-}}$ cross sections while no effect was observed in the ${\pi }^{+}$ cross sections. The cross sections were compared to predictions made by various optical model calculations. In general, both ${\pi }^{+}$ and ${\pi }^{\mathrm{-}}$ cross sections were poorly described and the ${\pi }^{\mathrm{-}}$ isotope effects were not well reproduced. Anomalous effects first observed in pionic atoms may also appear in the present data.

Measurements of cross sections for the (${\pi }^{+}$,${\pi }^{\mathrm{-}}$) reaction to the double isobaric analog state on targets of ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{34}{}_{}{}^{}\mathrm{S}$, ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$, ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$, and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ at ${\theta }_{\mathrm{lab}=5\mathrm{}}$° and an incident pion kinetic energy of ∼292 MeV are presented. We also present limits for the cross section to the residual ground state for the four T>1 targets. The data are compared with a phenomenological two-amplitude model and with a two-amplitude model that uses seniority-zero shell-model wave functions. The latter model provides expressions for both ground state and double isobaric analog state cross sections.

Proton-induced spallation reactions are studied in the energy region from 300 MeV to 20 GeV. An analytical expression is derived for the production cross sections of target residues in which the incident proton energy dependence of the cross sections is described by variation of a single parameter. Rather good agreement is obtained with experiment when reasonable physical assumptions for the variation of this parameter are made.

A general Poincaré invariant potential model for two-particle systems is constructed within the framework of light front dynamics. The model specifies all ten of the generators that are necessary to satisfy the Poincaré algebra. Formal expressions for the scattering states are constructed, and it is verified explicitly that they transform correctly under Lorentz transformations. The S-matrix elements are shown to be Lorentz invariant functions of the initial and final four-momenta of a scattering process. The T matrix is found to satisfy an integral equation that has the mathematical simplicity of its nonrelativistic counterpart.

The influence of the conventional nuclear structure on the European Muon Collaboration effect is critically reviewed. The ratio of deep inelastic lepton nucleon to lepton nucleus cross sections is shown to be sensitively dependent on the proper kinematics of the Fermi motion and the careful treatment of the binding effect of nucleons in nuclei. We systematically consider the example ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at -$Q^2$=20 (GeV/c${)}^2$.

The beta spectrum of ${}_{}{}^{63}{}_{}{}^{}\mathrm{Ni}$ was studied with a π √2 beta spectrometer, a multistrip source, and multidetector array. No evidence was found for heavy neutrinos with masses ranging from 4 to 40 keV. The upper limit, including numerical evaluation of systematic errors, for the mixing of a 17 keV neutrino was set at 0.3% (90% confidence level). The beta spectrum endpoint was found to be 66.946±0.020 keV, about 1 keV higher than the value derived from the 1983 atomic mass table, 65.92±0.15 keV.

Levels in ${}_{}{}^{136}{}_{}{}^{}$,138,140Sm were populated by the beta decay of Eu, following (HI,pxn) reactions and on-line mass separation. The beta decay of ${}_{}{}^{136}{}_{}{}^{}\mathrm{Eu}$ with a half-life of 3.9(±0.5) s was observed for the first time. Members of the γ band were observed in all three daughter nuclei. Spectroscopic calculations were made using the triaxial rotor model, with all parameters derived microscopically from a Woods-Saxon deformed shell model. Other spectroscopic models were also considered. Comparison with the data supports the characterization of these nuclei in terms of a triaxial intrinsic shape.

Nuclear β decays of highly ionized atoms under laboratory conditions are studied. Theoretical predictions of β-decay rates are given for a few cases in which bound-state β decay produces particularly interesting effects. A possible storage-ring experiment is proposed for measuring bound-state β-decay rates, which will be most easily applied to the decay of ${}_{}{}^3{}_{}{}^{}$${\mathrm{H}}^{+}$. .AE

The α decay of ${}_{}{}^{194}{}_{}{}^{}\mathrm{Pb}$ [$E_{\alpha }$=4.64±0.02 MeV, α branch=(7.3±2.9)×${10}^{\mathrm{-}6}$%] was identified for the first time, and a comprehensive decay scheme was constructed for the isotope’s β-decay branch. This scheme consists of 29 excited levels built on the $2^{\mathrm{-}}$ ${}_{}{}^{194}{}_{}{}^{}\mathrm{Tl}$ ground state and incorporates 91 γ-ray transitions. Based on the decays of several strong transitions, the half-life of ${}_{}{}^{194}{}_{}{}^{}\mathrm{Pb}$ was measured to be 12.0±0.5 min. The ${}_{}{}^{194}{}_{}{}^{}\mathrm{Pb}$ α reduced width, calculated with these data, is less than those of Pb, Hg, and Pt nuclei with A≤192, indicating that the Z=82 gap is perhaps being restored for N≥112.

An on-line isotope-separator facility has been used to determine the energies and intensities of sixteen γ rays following the ${\beta }^{\mathrm{-}}$ decay of the recently discovered isotope ${}_{}{}^{159}{}_{}{}^{}\mathrm{Sm}$. From these data, the existence of a new level in ${}_{}{}^{159}{}_{}{}^{}\mathrm{Eu}$ at 1051.80 keV has been established, and tentatively assigned as the ${(7/2\mathrm{}}^{\mathrm{-}}$[523] bandhead. The ${}_{}{}^{159}{}_{}{}^{}\mathrm{Sm}$ ground state is tentatively assigned as the ${(5/2\mathrm{}}^{\mathrm{-}}$[523] Nilsson state. Some of the deduced features of the reduced γ-ray transition probabilities as they relate to the proposed rotational-band structure in ${}_{}{}^{159}{}_{}{}^{}\mathrm{Eu}$ are briefly discussed.

State and level densities with fixed exciton numbers were estimated using combinatorial calculations. Shell-model orbitals were used as a basis from which all possible configurations were generated. The pairing interaction was taken into account by applying the BCS theory to each configuration. The spin and parity distributions were obtained. The role of the pairing interaction was understood and a method of treating pairing effects in practical reaction calculations is given. The spin and parity distributions were obtained and analyzed. The assumption of a Gaussian distribution for the spin projections was found to be valid for states containing at least four quasiparticles. The energy, spin, and parity distributions of states with low exciton numbers reveal strong fluctuations which are not predicted by closed formulae derived from the equidistant single-particle-level model. Effects of the restriction limiting configurations to only bound orbitals are discussed. The restriction decreases the possible spins of highly excited ‘‘bound’’ states compared to those of the unrestricted states.

The thermostatic properties of polarized nuclear matter are calculated using an extended form of the Seyler-Blanchard potential. Different special cases of polarized nuclear matter are considered according to the values of X, Y, and Z, the neutron excess parameter, and the sum and difference of neutron and proton spin up excess parameters, respectively. The reliability of the $T^2$ approximation is also discussed. A reasonable agreement with previous results is obtained.

We consider a one-dimensional model of nuclear matter where the quark clusters are described by solutions of the sigma model on a linear lattice in the self-consistent mean field approximation. Exact expressions are given for the baglike solutions confined to a finite interval, corresponding in the infinite interval limit to the free solitons previously found by Campbell and Liao. Periodic, self-consistent solutions which satisfy Bloch’s theorem are constructed. Their energies and associated quark sigma field distributions are calculated numerically as functions of the baryon spacing, and compared with those of the uniform quark plasma. The predicted configuration of the ground state depends critically on the assumed manner of filling the lowest band of quark single-particle levels, and on the density. In the absence of additional repulsive forces in the model, we find that the high density massless quark plasma is energetically favored and that there is a smooth transition from the baglike state to a uniform plasma with nonvanishing sigma field at comparatively large lattice constants 2d≊10$m_q^{\mathrm{-}1}$ ($m_q$ is the quark mass). If dilute filling of the entire band is employed, the clustered state is stable and a first order phase transition can occur for a range of much smaller lattice spacings 2d≊4$m_q^{\mathrm{-}1}$. .AE

A new technique of atom-photon coincidence laser spectroscopy has been developed and used to study the isotope shifts of ${}_{}{}^{78\mathrm{-}84}{}_{}{}^{}\mathrm{Sr}$. The results show that neither the droplet model nor existing interacting boson model calculations can adequately describe the rapid onset of nuclear deformation below N=50. The odd-even staggering of the charge radius is found to be opposite to that normally encountered, indicating the possible existence of permanent octupole distortions.

Isoscalar giant resonances in fast rotating nuclei are investigated within the framework of nuclear elasticity by solving the equation of motion of elastic nuclear medium in a rotating frame of reference. Both Coriolis and centrifugal forces are taken into account. The nuclear rotation removes completely the azimuthal degeneracy of the giant resonance energies. Realistic large values of the angular velocity, which are still small as compared to the giant resonance frequencies, are briefly reviewed in relation to allowed high angular momenta. It is shown that for the A=150 region, the Coriolis force is dominating for small values (≲0.05) of the ratio of angular velocity to resonance frequency, whereas the centrifugal force plays a prominent part in the shift of the split resonance energies for larger values of the ratio. Typical examples of the resonance energies and their fragmentation due to both rotation and deformation are given.

A generalization of the time dependent Hartree-Fock approach is presented. The corresponding extension is made by recourse to standard tools of statistical mechanics and allows for a wider scope of applications in comparison with the conventional treatment. The method is illustrated with reference to an exactly solvable U(n) model, with numerical examples presented for the case n=3.

Spectral distribution calculations of the level density of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ are compared with experimental values for the level density of this nucleus as well as with Fermi gas calculations. Particular attention is paid to the technique used for the expansion. Traditional techniques which have utilized knowledge of the third and fourth moments of the Hamiltonian have yielded a distribution function that is not positive definite. Two alternative expansion methods are examined. One is found to be unacceptable because of the fact it does not yield a unique fit, but the second appears to be quite useful. Not only is the resultant expansion positive definite, but it appears capable in principle of giving a more detailed representation of the level density than the traditional method. Results of the calculation for two different basis sizes are compared.

Within the relativistic Dirac-Brueckner approach we discuss the properties of highly-energetic nucleons and deltas in dense nuclear matter. The effective NN and NΔ interactions are constructed in a fully self-consistent way and reproduce all known properties of nuclear matter. We calculate the nucleon self-energy and the density-dependent effective NN and NΔ cross sections in a nuclear medium. Results show a sizable reduction of the Δ (pion) production cross section and important changes in the Δ absorption cross sections.

The ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$(γ,n) cross section has been measured from 9.6 to 18.8 MeV with monoenergetic photons. These new data resolve the discrepancies between the results of two previous measurements of this reaction cross section.

Photoemission of protons from ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ is measured at ${\theta }_{\mathrm{p}=30\mathrm{}}$°, 60°, 90°, and 105° in the photon energy range between 187 and 427 MeV. From the analysis of the momentum spectrum of protons, the differential cross sections for the photodisintegration of quasifree two-nucleon systems in the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ nucleus are deduced as a function of the proton angle and the incident photon energy. The obtained cross sections for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are larger than those for the deuteron photodisintegration by a factor of about 4.5 in the energy region of the present experiment.