Total fast particle yields for 33 isotopes ranging from protons to ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ emerging from the bombardment of ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ with 400 MeV ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ ions are analyzed in terms of Fisher’s theory for phase transitions from liquid to gas. The parameters obtained are close to those from GeV proton bombardment of heavy nuclei. The data infer a critical temperature of 5.0 MeV.

With the relativistic Boltzmann equation as a basis, we present a physically transparent theoretical approach to hadron and light fragment production in high energy nucleus-nucleus collisions. By use of multiple scattering expansion techniques and methods of transport theory, in combination with considerations from statistical thermodynamics, we arrive at a simple and practical model. Its flexibility and usefulness is demonstrated by a comparison with a variety of experimental data in the bombarding energy range of 400 MeV/nucleon to 2.1 GeV/nucleon.

Results are presented for time-dependent Hartree-Fock calculations of mostly head-on collisions of ${}_{}{}^{86}{}_{}{}^{}\mathrm{La}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. These studies demonstrate the sensitivity of the time-dependent Hartree-Fock dynamical fusion thresholds to the effective two-body interaction used in the calculations. The main thrust of this paper is to investigate the dynamical threshold which is the microscopic analog of the macroscopic extra-push threshold. We find that, for head-on collisions at bombarding energies above the interaction barrier, the onset of fusion is extremely sensitive to the interaction used. The thresholds calculated with different Skyrme forces differ by several hundreds of MeV or more, and are related to the effective mass of the interaction. We also show that the high-energy angular momentum window threshold has a pronounced force dependence, a feature which must be properly taken into account in comparing time-dependent Hartree-Fock window predictions with experimental data. Finally, it is shown that the fusion behavior can be sensitive both to the numerical time step used and to the precision of the calculation, a problem which may have implications regarding the validity of the time-dependent Hartree-Fock results after time scales of the order of ${10}^{\mathrm{-}20}$ s.

Target-like reaction products corresponding to the transfer of one or several nucleons have been measured as a function of the total kinetic energy loss in the reactions ${}_{}{}^{208}{}_{}{}^{}\mathrm{Ni}$ (1215 MeV) and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Ni}$ (1107 MeV) with a focusing time-of-flight spectrometer which provided a unique mass and charge separation and good energy resolution. The analysis of the experimental data covered the range from elastic scattering to deep-inelastic collisions. In the quasielastic region, neutron transfer dominates. The transfer probabilities as a function of the distance of closest approach can be described by a semiclassical theory of tunneling. Quasielastic transfer from the Ni targets to the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ projectile is strongly inhibited by the reaction Q values. For the intermediate and deep-inelastic collisions, the mean values and variances of the mass and charge distributions as a function of the dissipated energy, as well as the correlations between neutron and proton transport, are discussed in a statistical diffusion theory. The important influence of the static potential energy surface on nucleon transport in the deep-inelastic region is demonstrated. Deviations from the simple diffusion model, observed at small to medium energy losses, are discussed.

Using γ-ray photopeak intensities, excitation functions of one-neutron transfer to excited states in reaction products have been measured from about 20% and 15% below the fusion barrier to above barrier energies for ${}_{}{}^{58}{}_{}{}^{}$Ni${+\mathrm{}}^{64}$Ni and ${}_{}{}^{64}{}_{}{}^{}$Ni${+\mathrm{}}^{64}$Ni reactions, respectively. For ${}_{}{}^{58}{}_{}{}^{}$Ni${+\mathrm{}}^{64}$Ni, the one-neutron transfer cross section is greater than 1 mb at 20% below the barrier. The results are well described by distorted-wave Born approximation calculations using spectroscopic factors deduced from light-ion transfer measurements.

Fission of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$, and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ induced by both positive and negative pion beams at incident energies of 60 to 100 MeV is examined. Energy and mass spectra and angular correlations of coincident fission fragments are compared to theoretical calculations and to other data. Excitation energies of the fissioning system in excess of 100 MeV are deduced, implying that the fission examined in this study is caused primarily by true absorption of the pion. The masses of the coincident fission fragments are found to have a wider distribution than those from fissioning systems of similar excitation energy induced by nucleon beams. The fission cross sections are close to the reaction cross sections for ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ and scale with the fissility for the other nuclei studied.

The fractional cumulative yield of ${}_{}{}^{121}{}_{}{}^{}\mathrm{Ag}$ and the fractional independent yields of ${}_{}{}^{121}{}_{}{}^{}\mathrm{Cd}$, ${}_{}{}^{121}{}_{}{}^{}\mathrm{In}$, and ${}_{}{}^{121}{}_{}{}^{}\mathrm{Sn}$ from thermal-neutron-induced fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ were determined radiochemically to be 0.12±0.05, 0.61±0.09, 0.24±0.08, and 0.03±0.04, respectively. The yield values were used to determine the nuclear-charge-distribution parameters ${\sigma }_Z$=0.55±0.10 and ΔZ=0.50±0.05 for A=121. The ${\sigma }_Z$ for A=121 is close to ${\sigma }_Z$¯=0.52±0.02 for high-yield fission products, and no evidence for an even-odd Z effect was found for A=121. The positive ΔZ value, which corresponds to $Z_P$=48.15, is similar to those for several higher mass numbers reported previously, and it is considerably greater than the negative values predicted by the scission-point theoretical model. The use of a separation distance between nascent fragments greater than 1.4 fm, the value used in the theoretical calculations, could reduce the discrepancy and could also account for the observed enhanced independent yields of tin fission products with $Z_P$ near 50 (A=126–129).

A Lorentz invariant form of the NN amplitude is fit with a simple model which includes direct and exchange first Born terms from a number of ‘‘mesons.’’ The (complex) couplings and nucleon-meson form factors are adjusted to fit the NN amplitudes directly without iteration. The resulting parameters agree well with one-boson-exchange potentials and have a systematic and small energy dependence. Detailed analytic representations of the relativistic NN amplitudes are provided at lab energies of 135, 200, and 400 MeV. The model separation of the NN amplitudes into direct and exchange contributions does not involve sensitive cancellations and is contrasted with the very different nonrelativistic results. The model amplitudes are used to construct optical potentials in a relativistic impulse approximation using both pseudovector and pseudoscalar π-N coupling. The pseudoscalar result reproduces earlier relativistic impulse approximation calculations which diverge at low energies, while the pseudovector results are nearly constant with energy and in good agreement with phenomenological potentials.

Equations of the coupled-channel method are solved in momentum space for pion scattering on ${}_{}{}^{24}{}_{}{}^{}$,26Mg and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ in the ${\Delta }_{33}$-resonance region. The elastic and inelastic differential cross sections are calculated by using the nuclear ground-state and transition densities which correctly describe the (e,e’) data for the same nuclear states. Also calculated are the double-analog double-charge-exchange reactions ${}_{}{}^{26}{}_{}{}^{}({\pi }^{+}$,${\pi }^{\mathrm{-}}$)${}^{26}$ Si and ${}_{}{}^{18}{}_{}{}^{}({\pi }^{+}$,${\pi }^{\mathrm{-}}$)${}^{18}$ Ne, and the results obtained are in surprisingly good agreement with the experimental data. From the comparison of our coupled-channel and distorted-wave impulse approximation results we conclude that the multistep mechanisms play a minor role in the reactions considered.

Strange particle abundances in small volumes of hot hadronic gas are determined in the canonical ensemble with exact strangeness and baryon number conservation. Substantial density and baryon number dependence is found. A p¯d experiment is examined and applications to p¯-nucleus annihilations are considered.

An analysis is carried out of a π-N-Δ field theory using an extension of the Feshbach projection operator technique in conjunction with a set of identities which relate Green’s functions acting in subspaces whose projection operators are related by the action of the meson creation and annihilation operators. Exact relations are derived for the propagators, self-energies, and vertex functions that arise in the field theory. A separation of the pion-nucleon elastic scattering amplitudes into their one-particle irreducible and one-particle reducible parts is obtained. An exact set of coupled integral equations for the pion-nucleon amplitudes is derived. When a certain approximation for the effective potentials in these equations is made, it is found that the one-particle irreducible amplitudes satisfy a set of three-particle equations that are exactly analogous to the quasiparticle equations of Alt, Grassberger, and Sandhas. Moreover, the one-particle reducible parts can be obtained from the solutions of the three-particle equations. These equations are nonlinear in that the kernels are determined by the solutions. An approximate set of linear equations is obtained whose solutions satisfy two-particle and three-particle unitarity and have reasonable analytic structure. An iteration scheme for improving on the linear approximation is presented.

The polarization observables of the reactions parrow parrow → ${\pi }^{+}$d, parrowp → darrow${\pi }^{+}$, and πdarrow → πdarrow are investigated. Expressions relating these observables directly to (LSJ) partial wave amplitudes are derived and tabulations of the partial wave contributions are given for some of the observables. Examples are given of how such tabulations can be useful for optimizing the connection between theory and experiment and in suggesting possible new experiments. All observables are also calculated numerically using a unitary few-body model of the NN-πNN system to generate the amplitudes. Sensitivity to the choice of $P_{11}$ interaction is investigated.

The effect Δ$B_c$ of the Coulomb interaction on the Λ separation energy $B_{\Lambda }$ of ${}_{\mathrm{\Lambda }}{}^4{}_{}{}^{}\mathrm{He}$ was obtained by variational calculations made for ${}_{\mathrm{\Lambda }}{}^4{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. These calculations were made for several values of $q^2$ in the range 0≤$q^2$≤9 where qe is the proton charge, i.e., the Coulomb repulsion was artificially boosted. For $q^2$≲3, the dependence on $q^2$ is linear, and interpolation to $q^2$=1 gives the physical values with improved accuracy: -Δ$B_c$=0.05±0.02 and 0.025±0.015 MeV for the ground and excited state, respectively. This procedure also gives more accurate values for the differences between the proton and neutron radii of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. The corresponding differences of $B_{\Lambda }$ between ${}_{\mathrm{\Lambda }}{}^4{}_{}{}^{}\mathrm{He}$ and ${}_{\mathrm{\Lambda }}{}^4{}_{}{}^{}\mathrm{H}$, to be attributed to charge symmetry breaking effects, are then 0.40±0.06 and 0.27±0.06 MeV. From these values we obtain a phenomenological charge symmetry breaking potential which is effectively spin independent. An examination of meson-exchange charge symmetry breaking models shows that these are consistent with the phenomenological charge symmetry breaking potential for the triplet but not for the singlet case.

The sensitivity of intermediate energy ${\mathrm{K}}^{+}$ meson-induced elastic and inelastic differential cross section predictions to nuclear structure effects in the nuclear interior is examined for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ targets. The observed sensitivity for ${\mathrm{K}}^{+}$ mesons is compared to that obtained with intermediate energy protons. In general, the ${\mathrm{K}}^{+}$ meson+nucleus elastic and inelastic scattering differential cross sections are an order of magnitude more sensitive to details of nucleon density distributions in the nuclear interior than corresponding proton-nucleus cross sections at comparable incident momentum. It is found that theoretical analyses of high quality ${\mathrm{K}}^{+}$ meson+nucleus data which extend to 3 ${\mathrm{fm}}^{\mathrm{-}1}$ momentum transfer could, in principle, provide new information regarding neutron ground state and transition density distributions in the interiors of large nuclei.

We have reexamined the question of what limit may be placed on the free space neutron-antineutron oscillation time ${\tau }_{\mathrm{nn}\mathrm{¯}}$ from a measured limit $T_0$ on the annihilation lifetime T of a nucleus. Using several recent antinucleon-nucleus optical potentials consistent with both p¯-atom and low energy scattering data, we obtain a limit ${\tau }_{\mathrm{nn}\mathrm{¯}>(1\mathrm{}\pm 0.3)\times {10}^8}$ sec if $T_0$=2.4×${10}^{31}$ yr. We consider the effect on our results of nuclear medium corrections such as a renormalization of the effective operator for n→n¯ transitions or the presence of additional ΔB=2 decay modes which are absent in free space. It is argued that renormalization effects are not likely to exceed those characteristic of nuclear β decay, and that if additional modes are present, the limit on ${\tau }_{\mathrm{nn}\mathrm{¯}}$ becomes even better.

We invoke the formalism developed by Krajcik and Foldy to consistently treat recoil effects in the relativistically corrected impulse approximation in the presence of a local central potential. It is stressed that recoil effects in the case of the single-particle Dirac Hamiltonian are considerably different from those suitable for the Foldy-Wouthuysen diagonalized Hamiltonian. It is also found that, for the diagonalized Hamiltonian, intuitive arguments may result in an incorrect sign for certain terms as in a preceding paper. As an illustrative numerical example, we use the resultant formulae to determine the magnetic moment and charge radius of the ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ nucleus.

A simple relativistic extension of the first-order multiple scattering mechanism for the optical potential is employed within the context of a Dirac equation description of elastic nucleon-nucleus scattering. A formulation of this problem in terms of a momentum-space integral equation displaying an identifiable nonrelativistic sector is described and applied. Extensive calculations are presented for proton scattering from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at energies between 100 and 500 MeV. Effects arising from the relativistic description of the propagation of the projectile are isolated and are shown to be responsible for most of the departures from typical nonrelativistic (Schrödinger) results. Off-shell and nonlocal effects are included and these, together with uncertainties in the nuclear densities, are shown not to compromise the characteristic improvement of forward angle spin observable predictions provided by the relativistic approach. The sensitivity to ambiguities in the Lorentz scalar and vector composition of the optical potential is displayed and discussed.

Forward-angle differential cross sections for the isobaric-analog-state transition, ${}_{}{}^7{}_{}{}^{}$Li(${\pi }^{+}$,${\pi }^0$${)}^7$Be, were measured at 33.5, 41.1, 48.7, and 58.8 MeV. A minimum in the excitation function of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ at 42.3±1 MeV reflects the analogous minimum in the free πN cross section, which, according to current phase-shift analyses, is between 45 and 50 MeV. The data are compared with optical-model calculations.

Theory is given for momentum transfer to an ensemble of particles by incident neutrinos or antineutrinos in such a way that subsequent measurements cannot reveal the detailed characteristics of this transfer. It is shown that large scattering cross sections may be obtained, proportional to the square of the number of scatterers.

Nucleon-Dirac potentials are calculated from two-body-quark–one-boson-exchange potentials in the limit where the projectile nucleon is taken to be pointlike. Effective NN¯ pair effects in this model originate from the single-qq¯-pair mechanism.