Using the two-parameter expression for rotational spectra, E(I)=a[ √1+bI(I+1) -1], derived from the Bohr Hamiltonian, the spins of 22 superdeformed bands observed in the A∼190 region were determined. The calculated transition energies depend sensitively on the prescribed spins. The agreement between the calculated and observed transition energies is incredibly well when a correct spin assignment is made. The kinematic and dynamic moments of inertia were extracted from the observed transition energies and their variation with rotational frequency was investigated.

Although the tensor interaction in the first order does not affect the single-particle splitting for closed LS shell nuclei, e.g., ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, it causes the j=l-1/2 member of a spin-orbit pair to come towards or even below the j=l+1/2 member for an open shell. With the bare Bonn A interaction, the splitting ${\mathrm{\epsilon }}_{\mathit{p}1/2}$-${\mathrm{\epsilon }}_{\mathit{p}3/2}$ is 4.2 MeV for an ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ core but is -3.0 MeV for a closed ${\mathit{p}}_{3/2}$ core of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. In large space shell-model calculations, this single-particle energy inversion leads to too high an occupancy of the ${\mathit{p}}_{1/2}$ orbit and pushes the wave functions of the low-lying states too much towards the LS limit. This manifests itself in too low a magnetic dipole transition rate from the ground state ($0_1^{+}$) to the $1_1^{+}$, T=1 state. Various mechanisms are investigated in attempts to cure this problem including the relativistic effects of the Dirac-Brueckner-Hartree-Fock approach, also the effects of core polarization on the effective interaction and finally the effects of changing the meson masses in the nuclear medium as parametrized in the Hosaka-Toki interaction. The Dirac effects tend to increase the spin-orbit interaction while the change of the meson masses yields a weaker effective tensor force. Both effects improve the results of the nuclear structure calculations. The core polarization graphs involving phonon exchange also improve the results but other graphs, e.g., particle-particle ladders and hole-hole diagrams work in the opposite direction.

Relations between the ${\mathrm{Spin}}^{\mathrm{BFF}}$(6) symmetry Hamiltonian for odd-odd systems and the interacting boson-fermion-fermion model (IBFFM) Hamiltonian are investigated. An exact equivalence is established by slightly revising the exchange term of the IBFFM Hamiltonian. The ${\mathrm{Spin}}^{\mathrm{BFF}}$(6) symmetry is realized approximately in IBFFM by extending the quasiparticle configuration space for odd fermions. The proton-neutron residual interaction associated with the appearance of dynamical symmetry is compared to effective proton-neutron forces.

The doubly differential cross section for the production of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ by 800 MeV protons from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, Ti, and Pb has been measured at laboratory angles of 6° and 15°. The momentum of the detected helium nuclei varied from 1 to 2 GeV/c, the maximum being well above the incident proton momentum of 1.46 GeV/c. The cross sections were found to increase with increasing target mass and decrease with increasing momentum and scattering angle. In our momentum region, the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ production cross section is 1.5–10 times larger than ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ depending on the target and the momentum. The data are consistent with the hypothesis that the dominant reaction mechanism is a direct process where the initial nucleon-nucleon scattering is followed by a sequential pickup of neutrons.

The energy dependence of rapidity distributions and flow effects was studied in central Ar+Pb collisions at 400, 800, and 1800 MeV/nucleon using a streamer chamber. Rapidity distributions for proton and pions are found to have a Gaussian shape whereas those for deuterons exhibit a two-peak structure at the two higher energies. The average in-plane transverse momentum per/nucleon and per/event shows saturation of flow around 800 MeV/nucleon for this asymmetric system. The aspect ratio of the sphericity tensor is closely correlated with the flow angle. This correlation appears to be independent of beam energy. The number of participating nucleons in central collisions varies from 213 at 400 to 135 at 1800 MeV/nucleon indicating that at the lowest energy almost the entire target nucleus participates in the collision.

Coincidence analyzing-power measurements or asymmetries ${\mathit{A}}_{\mathit{x}}^{\mathrm{coinc}}$, ${\mathit{A}}_{\mathit{y}}^{\mathrm{coinc}}$, and ${\mathit{A}}_{\mathit{z}}^{\mathrm{coinc}}$ are presented for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(p→,p’γ${)}^{12}$${\mathrm{C}}^{\mathrm{*}}$ (15.11 MeV) reaction. A polarized proton beam at 318 MeV was used and data were obtained for three mutually perpendicular directions of polarization. A scintillator hodoscope was used for detecting scattered protons and four BGO detectors for the 15.11-MeV γ rays. Data are presented for eight azimuthal directions of the scattered protons around the beam direction, and for the polar angles averaged between 3.3° and 11.2°. The data are compared with both nonrelativistic and relativistic calculations. The average size of the asymmetries measured is somewhat less than both predictions and the results do not agree clearly with either prediction.

The total energy dissipated in central collisions has been measured for the system ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$${+}^{58}$Ni at about 1 GeV incident energy. An event-by-event reconstruction of the atomic charge of the reaction products was performed by means of a 4π charged-particle detector. Two distinct classes of events were thus separated: one consistent with a ‘‘conventional’’ incomplete fusion-evaporation process; a second where three or more heavy fragments are produced. A subtraction of the evaporative component from the particle spectra at all angles allowed extraction of the excitation energy removed from the system by pre-equilibrium emission. The average excitation energies corresponding to the two different classes of events were determined. Comparisons with statistical model calculations as well as a multifragmentation model are presented.

Spin-spin cross sections were measured for 7.5-MeV polarized neutrons incident on cryogenically polarized ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$. Measurements were made with spin orientations transverse and longitudinal to the beam direction, yielding ${\mathrm{\sigma }}_{\mathit{T}}^{\mathit{s}\mathit{s}}$=-5.2±5.3 mb and ${\mathrm{\sigma }}_{\mathit{L}}^{\mathit{s}\mathit{s}}$=-2.2±6.9 mb, respectively. The results are consistent with recent valence-nucleon folding model calculations. The tensor spin-spin potential is found to be small, ${\mathit{V}}_{12}$=-67±190 keV. Volume integrals of spin-spin potentials are derived from depolarization and transmission experiments on ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$. The results for the central spin-spin potential are shown to be consistent with the folding model predictions.

The proton-carbon bremsstrahlung (p ${}_{}{}^{12}{}_{}{}^{}\gamma$) cross sections as a function of photon energy have been measured at the incident proton energy of 2.135 MeV for two proton scattering angles: one at 155° and another one at 175°. We have extended the range of photon energy up to about 1.7 MeV, which is near the maximum photon energy, in order to study all possible resonant structures. Two resonant structures have been observed in the bremsstrahlung spectrum. The first is identified as the structure due to the 1.7-MeV elastic ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ scattering resonance and the second is attributed to the 0.5-MeV resonance. These measured ${\mathit{p}}^{12}$Cγ spectra with the detailed information about the resonant structure have been used to test the range of validity of various soft-photon approximations. We have found that our data can be described by a special two-energy–two-angle approximation, which depends on one elastic T matrix evaluated at the initial energy (or total energy squared) and another elastic T matrix evaluated at the final energy, but the approximation is free of any derivative of the elastic T matrix with respect to energy or scattering angle (or momentum transfer squared). Our study also shows that the resonant structure predicted by the one-energy–one-angle approximation disagrees with the experimental data.

Intermediate mass fragment (IMF: 3≤Z≤20) emission for the ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$${+}^{197}$Au reaction at E/A=35 MeV has been studied with a low-threshold 4π charged-particle detector array covering the angular range of 16°≤${\mathrm{\theta }}_{\mathrm{lab}}$≤160°. While most IMF’s are emitted in central collisions characterized by large charged-particle multiplicities, contributions from peripheral collisions exist at forward angles which are reminiscent of damped collisions or emission from a projectile-like source. Energy spectra, angular distributions, element distributions, and two-fragment correlation functions are presented for various gates on the charged-particle multiplicity, and the time scale of fragment emission is deduced.

The spin-correlation observable ${\mathit{A}}_{\mathit{L}\mathit{L}}$ for p-p elastic scattering has been measured at energies 589, 640, 692, 743, and 793 MeV, over a c.m. angular range between 20° and 100°. The spin observable ${\mathit{A}}_{\mathit{S}\mathit{L}}$ was also measured in this angular range at energies 640 and 793 MeV. At 488 MeV both the spin observables were measured, but only near the c.m. angle of 90°. The data are compared with the predictions of several phase-shift analyses and previous measurements. The energy dependence of ${\mathit{A}}_{\mathit{L}\mathit{L}}$ for the c.m. angle of 90° is also presented and shows no anomalous behavior. These data provide better angular coverage over five of the energies, with comparable or better statistical precision, than previous measurements of ${\mathit{A}}_{\mathit{L}\mathit{L}}$.

The elastic scattering of negative pions with a momentum of 5 GeV/c from ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ is analyzed using a single-scattering optical potential in a relativistic integral scattering equation. The potential is computed using several nuclear and nucleon form factors as well as both phase-shift and exponential representations of the pion-nucleon amplitude. Predicted scattering observables are compared with experiment. The effect on the calculated observables due to an increase of effective nucleon size is also shown.

Formal solutions of the second-order amplitude in the Born approximation to the quantal, microscopic, many-body problem of pion production from the collision of equal-mass nuclei are presented where Δ-hole states are created in the intermediate nuclear states. The form factors containing nuclear structure information are solved in terms of particle-hole coefficients which describe any intermediate particle-hole state, regardless of whether it is coherent or incoherent. In this approach, the important tensor term has been included. A semiquantitative analysis is carried out which gives an indication of the approximate conditions under which pion production may be maximized under the excitation of Δ-hole states by the transition-spin, -isospin, one-pion-exchange interaction.

The cluster size distributions in proton-nucleus collisions and in nucleus-nucleus collisions are discussed using a simple exactly soluble model. These distributions can be characterized by a single parameter involving volume, temperature, binding energy, and level density effects. As this parameter varies, the shape of the distribution of cluster size changes. Good agreement is found between a simple theoretical prediction and experiment.

Employing a recently developed semiclassical nuclear model, based on a modified Seyler-Blanchard interaction depending on both momentum and density, we consider the thermostatic properties of hot isosymmetric nuclei embedded in a nucleon vapor. The level-density parameter is calculated and discussed. Simple analytical expansions are obtained for the dependence of the level-density parameter and the free energy on nuclear mass number and the temperature of the surrounding vapor. The model is employed for an illustrative study of the symmetric breakup of ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$ into a number of equal fragments.

In this paper we give the results of a relativistic analysis of elastic and inelastic scattering of 180 MeV antiprotons from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. The calculations are performed within a Dirac coupled-channel framework using a collective model for the transition potentials. While the presence of the inelastic data does seem to remove some of the ambiguity in the Dirac optical model potentials, the largest constraint comes from the elastic analyzing power measurements. In the Dirac approach for proton-nucleus scattering, spin observables are very important; this is also true for the determination of the antiproton-nucleus optical potential.

Information about the space-time characteristics of intermediate-mass fragment emission processes is contained in the shape of two-fragment correlation functions at small relative momenta. A classical approximation to the Koonin-Pratt formula is derived which allows the calculation of correlations resulting from the Coulomb interaction between the two detected fragments. Distortions in the Coulomb field of heavy reaction residues are evaluated by means of three-body Coulomb trajectory calculations.

We calculate differential cross sections for ${}_{}{}^4{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He elastic scattering at 4.32 GeV/c in the framework of Glauber multiple scattering theory using correlated variational wave functions as given by the two-nucleon Urbana ${\mathit{v}}_{14}$ potential and the spin-isospin averaged Melfleit-Tjon force V. These wave functions are found to give fairly satisfactory results.

We introduce a dynamical model for the description of hadron-hadron collisions at relativistic energies. The model is based on classical Nambu-Gotō strings. The string motion is performed in unrestricted four-dimensional space-time. The string end points are interpreted as partons which carry energy and momentum. We study ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$, e-p, and p-p collisions at various center-of-mass energies. The three basic features of our model are as follows. An ensemble of strings with different end-point dynamics is used to approximately reproduce the valence quark structure functions. We introduce an adiabatic hadronization mechanism for string breakup via qq¯ pair production. The interaction between strings is formulated in terms of a quark-quark scattering amplitude and exchange.

The mass of the quark alpha is estimated by giving the quark an effective mass, which is extrapolated from the three-quark configurations confined by a scalar plus vector harmonic potential. It is found that the quark alpha is not absolutely stable, although it may be exceptionally stable. Some of the consequences of its stability are discussed.