We analyze the physics of relativistic nuclear collisions and demonstrate that an adequate treatment of pions must include the quantum time-energy uncertainty principle and nonsequential three-body collisions. We apply relativistic quantum field theory to obtain exact equations determining the time evolution of hadronic fields and their fluctuations in terms of the effective interactions describing scattering in matter. These equations relate the main physical observables to the sought-after properties of nuclear matter, and involve only these quantities and the corresponding properties of free-space one- and two-body processes. We show how to regularize the singularities by employing the internal structure of the mesons, while maintaining causality and unitarity. We show that, in a very good approximation, the dynamic quantities reduce to functions of eight variables—those of the Boltzmann equation, supplemented by the energy of the hadron. Our method appears capable of deducing the properties of hot dense nuclear matter from data already measured in experiments on the collisions of heavy nuclei.

Excited states in ${}_{}{}^{75}{}_{}{}^{}\mathrm{Kr}$ were populated via the reaction ${}_{}{}^{46}{}_{}{}^{}\mathrm{S}$,2pn) at a beam energy of 97 MeV. Several new high-spin states were found. Evidence for band crossings was found in both the positive- and negative-parity bands. Calculations using a cranked Strutinsky-Bogolyubov model with a Woods-Saxon potential indicate noticeably different deformations for the opposite parity bands: ${\beta }_2$=0.40, γ=-8° for the positive-parity band and ${\beta }_2$=0.36, γ=3° for the negative-parity band. These deformations are comparable to superdeformations reported by other authors in the cerium region. Signature splitting in both positive- and negative-parity bands was well reproduced by the calculations. Indirect evidence suggests shape coexistence within the positive-parity band at low spin.

We propose a modified statistical model describing the disassembly of hot nuclei created in intermediate energy heavy-ion reactions. The calculated mass-yield distribution of fragments arising in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(E/A=35 MeV)${+}^{63}$Cu reactions agrees with experimental data quite well.

In order to improve existing I=0 phase shift solutions, the spin correlation parameter $A_{\mathrm{NN}}$ and the analyzing powers $A_{0N}$ and $A_{N0}$ have been measured in n-p elastic scattering over an angular range of 50°–150° (c.m.) at three neutron energies (220, 325, and 425 MeV) to an absolute accuracy of ±0.03. The data have a profound effect on various phase parameters, particularly the ${}_{}{}^1{}_{}{}^{}\mathrm{P}_1^{}{}_{}{}^{}$, ${}_{}{}^3{}_{}{}^{}\mathrm{D}_2^{}{}_{}{}^{}$, and ${\epsilon }_1$ phase parameters which in some cases change by almost a degree. With the exception of the highest energy, the data support the predictions of the latest version of the Bonn potential. Also, the analyzing power data ($A_{0N}$ and $A_{N0}$) measured at 477 MeV in a different experiment over a limited angular range [60°–80° (c.m.)] are reported here.

Inclusive quasielastic p→${+}^2$H analyzing-power and spin-rotation depolarization ($D_{\mathrm{ij}}$) data are reported for the nucleon-nucleon center-of-momentum angular ranges 46.9°–118.0° and 58.3°–110.0° at 647 and 800 MeV, respectively. Exclusive quasielastic p→p and p→n analyzing-power data and exclusive p→p $D_{\mathrm{ij}}$ data are also presented. A simple isospin weighting model successfully describes the inclusive data and is used to estimate the free p→n $D_{\mathrm{ij}}$ values. The new data are compared with those of previous experiments and with predictions of phase-shift analyses. The deduced p→n $D_{\mathrm{ij}}$ values extend the angular range of previous 800 MeV data and provide entirely new information at 647 MeV.

Small-angle differential cross sections for the (${\pi }^{+}$,${\pi }^0$) reaction have been measured at energies of 300, 425, and 500 MeV for the isovector giant dipole resonance in a range of targets. Peak differential cross sections are inferred by extrapolation in angle. The target-mass dependence of these cross sections, normalized to the expected sum rule, shows the same mass dependence at 425 MeV that is observed for isobaric analog state transitions.

Results on antiproton absorption at rest in gaseous nitrogen and deuterium are presented from an analysis of approximately ${10}^6$ events each taken with a magnetic spectrometer. Inclusive features such as pion and proton multiplicities and spectra are presented. Data relating to absorption modes requiring more than one nucleon, such as the Λ yield, the Λ spectrum, and the exclusive deuterium channels p¯d→${\pi }^{\mathrm{-}}$p, Λ$K^{+}$${\pi }^{\mathrm{-}}$ are discussed. The fully reconstructable channels p¯d→${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$${\mathrm{\pi }}^{\mathrm{-}}$p,${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{+}$ ${\mathrm{\pi }}^{\mathrm{-}}$${\mathrm{\pi }}^{\mathrm{-}}$${\mathrm{\pi }}^{\mathrm{-}}$p also show a high-energy proton tail unaccounted for by single nucleon rescattering mechanisms.

A phenomenological two-nucleon pion-absorption T matrix is used to calculate partial rates for absorption of negative pions from the 1s state of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ pionic atom. The T matrix depends on parameters $g_0$ and $g_1$, which describe absorption on s-wave triplet and singlet nucleon pairs, respectively. The partial rates considered are those feeding n+d, n${+}^1$(np${)}_0$, p${+}^1$(nn${)}_0$, and those nnp final states with no nucleon pairs of low relative energy. In addition, the differential rate to the nnp final state is calculated as a function of $T_n$ and $T_p$, observed neutron and proton kinetic energies, respectively, and is compared to experimental differential rates along selected straight lines in a Dalitz plot of event number density vs $T_n$ and $T_p$. Two different momentum space ground-state functions are used, both exhibiting the correct asymptotic behavior with respect to bound two-body and three-body channels but derived from wave functions in configuration space with and without hard-core nucleon-nucleon correlations. Agreement with a number of recent pion absorption experiments can only be obtained with the wave function containing hard-core correlations and only for small positive values of $g_1$/$g_0$, $g_1^2$/$g_0^2$<0.04, much smaller than the ratio $g_1^2$/$g_0^2$=0.30±0.15, which is consistent with the low-energy production cross sections for p+p→d+${\pi }^{+}$ and p+p→p+p+${\pi }^0$. It is suggested that the discrepancy arises because gamma rays from pp bremsstrahlung may have contributed significantly to the measured ${\pi }^0$ production cross sections and/or because single nucleon processes may play a significant role in low-energy absorption on singlet nucleon pairs.

We examine the model dependence and nuclear-structure sensitivity of several ${\Delta }_{33}$-dominated processes contributing to pion double charge exchange on nuclei in the region of the ${\Delta }_{33}$ resonance. These processes include the ${\Delta }_{33}$-nucleon interaction $V_{N\Delta }$ and sequential scattering, in which the pion undergoes single charge exchange on two different nucleons. In all cases, the scattering takes place through the exchange of an intermediate π and ρ meson. Sequential-mediated double charge exchange is found to be only moderately sensitive to short-range correlations, meson-nucleon form factors, and the rho meson, whereas $V_{N\Delta }$-mediated double charge exchange is very sensitive to all these effects. Results are given for double charge exchange on ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ (double isobaric analog transitions) and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ (nonanalog transitions). Sequential double charge exchange is shown to favor non-spin-flip matrix elements of the transition operator whereas $V_{N\Delta }$-mediated double charge exchange favors spin-flip matrix elements. The energy dependence of the zero-degree cross sections for $V_{N\Delta }$ and sequential scattering are also different: Sequential tends to increase monotonically from 100 to 300 MeV, whereas $V_{N\Delta }$ peaks at about 150 MeV. The delta-nucleon interaction is found likely to dominate over sequential scattering in nonanalog double charge exchange. The $V_{N\Delta }$ is also large in analog double charge exchange, but it does not enable us to explain the anomalous behavior of the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ differential cross sections.

There has been a long-standing problem in the coupled πNN-NN theory concerning its apparent failure in reproducing the tensor polarization $T_{20}$ in the elastic πd scattering at medium energies. A mechanism recently proposed by Jennings to solve this problem is examined. It is then found that it comes from the positive-energy pole in one of the nucleon propagators in the exchange impulse diagram within the covariant picture which is usually overlooked when devising the spectator on-mass-shell approximation, and that it does not lead to the claimed near cancellation of the Pauli exchange contribution, but is important to be included. The inclusion of this contribution is shown to considerably improve in reproducing the pion-deuteron spin observables including $T_{20}$, particularly above the delta resonance energy.

Angular distributions of the analyzing powers for ${\pi }^{+}$p→ and ${\pi }^{\mathrm{-}}$p→ elastic scattering have been measured in a single-scattering experiment employing a polarized proton target. Measurements were obtained for pion energies of 98, 139, 166, 215, and 263 MeV. The addition of these data to the existing πp database significantly reduces the uncertainties in all S and P phase shifts for πp reactions over the delta resonance.

The half-life of ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ has been determined in one series of experiments by simultaneously measuring the decay of the 847-keV γ-ray line relative to the 662-keV line of ${}_{}{}^{137}{}_{}{}^{}\mathrm{Cs}$ and the decay of the 1238-keV line relative to the 1275-keV line of ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$ in a Ge(Li) γ-ray detector. Data were taken for two half-lives of ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$. In a second series of runs, covering one ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ half-life, the decay of the 847-keV line was measured relative to the 898-keV γ ray of ${}_{}{}^{88}{}_{}{}^{}\mathrm{Y}$. By combining the results we obtain $T_{1/2}$=77.30(9) d for the half-life of ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$.

Isotope dilution mass spectrometry was used to measure the concentration of ${}_{}{}^{229}{}_{}{}^{}\mathrm{Th}$ in the National Bureau of Standards ${}_{}{}^{229}{}_{}{}^{}\mathrm{Th}$ radioactivity standard, Standard Reference Material 4328. From these data the half-life of ${}_{}{}^{229}{}_{}{}^{}\mathrm{Th}$ is determined to be 7880±120 yr. This value is approximately 7% greater than the presently accepted value of 7340±160 yr.

The ${\beta }^{+}$-EC decay of mass-separated ${}_{}{}^{133}{}_{}{}^{}\mathrm{Nd}$ ($T_{1/2}$=70 sec) is studied by gamma-ray and internal conversion electron spectroscopy ($e^{\mathrm{-}}$ and γ singles, γ-γ-t and $e^{\mathrm{-}}$-γ-t coincidences). Twenty new levels are proposed in ${}_{}{}^{133}{}_{}{}^{}\mathrm{Pr}$ up to an excitation energy of 2.06 MeV. The new level scheme includes a ground state which differs from previous assignments. The low-energy excitation structure of ${}_{}{}^{133}{}_{}{}^{}\mathrm{Pr}$ is compared with predictions of interacting boson-fermion model calculations.

The level structures of ${}_{}{}^{143}{}_{}{}^{}\mathrm{Ba}$ and ${}_{}{}^{147}{}_{}{}^{}\mathrm{Ce}$ have been investigated by studying the β decays of 1.8-s ${}_{}{}^{143}{}_{}{}^{}\mathrm{Cs}$ and 4.1-s ${}_{}{}^{147}{}_{}{}^{}\mathrm{La}$ to search for evidence of intrinsic reflection asymmetry in light rare-earth nuclei. Gamma-ray energies and relative intensity values, γ-γ coincidence intensities, and γ-γ angular correlation coefficients were measured. The parity doublets that characterize reflection asymmetric rotational structures in the light odd-A actinides were not readily identified in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Ba}$ or ${}_{}{}^{147}{}_{}{}^{}\mathrm{Ce}$. The observed level structures, combined with other data for these nuclides, suggest that weak deformation is present and that reflection asymmetric admixtures may play a significant role in driving that deformation.

Shell-model calculations are performed for the odd- and even-parity states of ${}_{}{}^{39}{}_{}{}^{}\mathrm{Cl}$ and the odd-parity states of ${}_{}{}^{39}{}_{}{}^{}\mathrm{S}$. The ${}_{}{}^{39}{}_{}{}^{}\mathrm{S}$ odd-parity states and the ${}_{}{}^{39}{}_{}{}^{}\mathrm{Cl}$ even-parity states were considered in full (1s,0d${)}^{20}$(0f,1p${)}^3$ and (1s,0d${)}^{21}$(0f,1p${)}^2$ configurational spaces, respectively. For the ${}_{}{}^{39}{}_{}{}^{}\mathrm{Cl}$ odd-parity states it was necessary to use a highly truncated (1s,0d${)}^{20}$(0f,1p${)}^3$ configurational space. The method and results of truncation are discussed in some detail. Observables calculated include energy spectra, binding energies, ${}_{}{}^{40}{}_{}{}^{}$Ar${\to }^{39}$Cl+p spectroscopic factors, first-forbidden and allowed ${\beta }^{\mathrm{-}}$ decay of ${}_{}{}^{39}{}_{}{}^{}\mathrm{S}$, and γ transitions in both ${}_{}{}^{39}{}_{}{}^{}\mathrm{S}$ and ${}_{}{}^{39}{}_{}{}^{}\mathrm{Cl}$. Results are compared to experiment. For example, the spectroscopic factors for ${1/2}^{+}$ and ${3/2}^{+}$ ${}_{}{}^{39}{}_{}{}^{}\mathrm{Cl}$ states and the γ transitions between the even-parity ${}_{}{}^{39}{}_{}{}^{}\mathrm{Cl}$ states are predicted with high accuracy while the half-life of ${}_{}{}^{39}{}_{}{}^{}\mathrm{S}$ is calculated to be 5.6 s (if the spin-parity of ${}_{}{}^{39}{}_{}{}^{}\mathrm{S}$ has the preferred value of ${7/2}^{\mathrm{-}}$) as compared to the experimental value of 11.5±0.5 s.

Charge distributions of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$, and ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$ have been calculated within the Hartree-Fock and Hartree-Fock+BCS approximations with the Skyrme interaction. Using the force ${\mathrm{SkM}}^{\mathrm{*}}$ designed without any reference to this particular problem, we find good agreement with elastic electron scattering data. The role of pairing correlations beyond the mean field is studied by applying the Lipkin-Nogami method of variation after approximate projection on the good number of particles. We argue in this paper that, in our opinion, there is no significant discrepancy between the experimental data and the Hartree-Fock calculations using reasonable effective interactions. In particular, we do not see any compelling need for a large depletion of the occupation number of the proton 3$s_{1/2}$ orbital.

We consider the symplectic structure of the collective manifold as it emerges in a path integral approach. We make use of the Hubbard-Stratonovich transformation in order to integrate out the fermionic degrees of freedom. The effective action obtained in this way is expressed in terms of the single-particle components of the one-body density or potential, which play the role of phase space variables. We show that the term usually designed as the quantum nonintegrable phase is the only term responsible for the definition of the symplectic structure on this manifold. Without this term the Poisson bracket on the collective manifold is undefined.

The ${\mathrm{SP}}_6$×${\mathrm{scrSscrU}}_2$ symmetry of the fermion dynamical symmetry model (FDSM) was studied. Analytic expressions are given for the wave functions and matrix elements of the pair creation operators $S^{\mathrm{°}}$, $D^{\mathrm{°}}$, and E2 transition operator for the heritage u=0, 1, 2 cases. Various Pauli effects which differentiate the FDSM ${\mathrm{SU}}_3$ from IBM ${\mathrm{SU}}_3$, as well as the relationship between the wave functions and matrix elements in the FDSM, the interacting boson model, the Sp (6,R) models, and the Elliott model are discussed. Extensive discussions of the physical implications of the model are presented.

The relation between the signature splitting of energies and the signature dependence of M1 transition matrix elements is investigated in connection with the deviation of nuclear shape from axial symmetry. The analysis of available experimental data on the signature dependences as well as the sign of E2/M1 mixing ratio of the ΔI=1 transition confirms our understanding of the structure of the rotational perturbation.