We report the first exclusive (γ,${\mathrm{\pi }}^{\mathrm{-}}$p) measurements on a complex nucleus. The ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(γ,${\mathrm{\pi }}^{\mathrm{-}}$p) reaction was measured at pion laboratory angles of 64° and 120°. Coincident protons were detected over the quasifree angular correlation range using a vertical array of seven plastic scintillator detectors spanning ±33° about the scattering plane. The cross sections are compared to factorized distorted-wave impulse approximation calculations; these provide a good description of the backward angle data, but are in serious disagreement with the forward angle data.

Giant dipole resonance (GDR) γ rays were measured in kinematic coincidence with fission fragments in the reactions ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{208}$Pb at 140 MeV, and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$${+}^{\mathrm{nat}}$W at 185, 215, and 230 MeV bombarding energy, leading to ${}_{}{}^{\mathrm{\sim }216,224}{}_{}{}^{}\mathrm{Th}$ at a temperature of T≊1.8 to 2.1 MeV. The experiment determined the γ-ray spectrum and the γ-ray-fission fragment angular correlation as a function of fragment mass, kinetic energy, and total kinetic energy release. The coincidence γ-ray spectra are fitted successfully and consistently in terms of the statistical decay of the hot compound system and of the fission fragments, when a large nuclear dissipation (γ=10) and, for the ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$${+}^{\mathrm{nat}}$W reaction, the GDR γ emission during the quasifission process is included. The γ-ray-fission fragment angular correlation indicates a deformed compound system in ${}_{}{}^{224}{}_{}{}^{}\mathrm{Th}$ of either strongly prolate (β=0.3) or noncollective oblate (β=-0.1) shape. This is consistent with, but does not prove, a transition to a liquid drop shape having occurred at T≊1.8 MeV. The quasifission process is successfully included using regular extra-push and extra-extra-push energies and a quasifission lifetime ${\mathrm{\tau }}_{\mathrm{QF}}$=(20–40)×${10}^{\mathrm{-}21}$ sec. This is about ten times shorter than the compound nucleus fission lifetime in ${}_{}{}^{224}{}_{}{}^{}\mathrm{Th}$ at this temperature.

In-plane and out-of-plane angular correlations have been measured between fragments of Z>3, Li fragments, ${}_{}{}^{3,4}{}_{}{}^{}\mathrm{He}$, and ${}_{}{}^{1,2,3}{}_{}{}^{}\mathrm{H}$. The changing patterns for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ induced reactions of 7A, 17A, 27A, and 34A MeV give an overview of the decreasing importance of mass-symmetric fissionlike reactions at the expense of a broad range of more mass-asymmetric breakups. Evidence is given that these fragments come from a central collision group of reactions that have similar violence and from which many combinations of fragments and particles are ejected. Very similar azimuthal angular correlations are observed for particles with a Li fragment and for particles with a pair of heavier fragments (Z>3). This similarity suggests comparable strengths of association with the reaction plane for single Li fragments and for fragment pairs of Z>3. Azimuthal angular correlations for Li-Li pairs exhibit distinct asymmetries; their interpretation via trajectory-model calculations indicates mean delay times of ≊5×${10}^{\mathrm{-}22}$ s.

We have measured the nuclidic production cross sections and recoil properties for intermediate mass fragments, fission fragments, and heavy residues from the interaction of 21 MeV/nucleon ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$ with ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$. From these measurements, we have deduced the fragment mass distributions and fragment velocities, momenta, etc. The fragment N/Z ratios, isomeric state populations, and mean fragment energies are similar to those observed in low energy, deep inelastic scattering. The stochastic nucleon exchange model correctly predicts the shape of the heavy residue mass distribution, but overestimates (by a factor of 2–3) the fragment longitudinal velocities as does the dissipative fragmentation model, perhaps due to the lack of preequilibrium emission in these models.

The total cross sections for ${\mathit{K}}^{+}$ mesons on carbon and deuterium nuclei have been measured at eleven momenta in the range 450–740 MeV/c. The experimental technique was of the standard transmission type. The ${\mathit{K}}^{+}$ meson is the least strongly interacting of available hadronic probes, with a long mean free path in nuclear matter. At low incident momentum the ${\mathit{K}}^{+}$N interaction is dominated by the ${\mathit{S}}_{11}$ phase shift and varies slowly with energy. These characteristics make the ${\mathit{K}}^{+}$ an ideal tool for probing the nuclear volume to reveal nuclear medium effects. Measurements of the ratio of the total cross sections, per nucleon, of ${\mathit{K}}^{+\mathrm{-}12}$C to ${\mathit{K}}^{+\mathrm{-}}$d have been suggested as a way to reveal effects of the nuclear medium. The total cross section ratios are found to lie significantly above those predicted by the usual nuclear medium corrections. This suggests that novel phenomena are taking place within the nucleus. Several models which incorporate such phenomena are discussed, including nucleon ‘‘swelling,’’ mass rescaling, nuclear pions, and relativistic effects.

Velocity spectra of heavy ions produced in the ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$${+}^{28}$Si reaction at 19.7 and 30 MeV/nucleon were measured and interpreted within the Q-optimum model. An important process at forward angles is the mutual excitation of projectile and target to energies localized in the region of (2–3)ħω excitations.

A theoretical analysis of collective momentum transfer is performed in heavy-ion reactions below 100 MeV/nucleon in the Landau-Vlasov approach. The nucleon-nucleon cross section, atomic mass, compressibility, and effective mass dependences are analyzed. The simulation of detector acceptances and of finite number of detected particles are discussed. In connection with recent experiments, theoretical results and experimental data are confronted taking into account the experimental constraints. Finite range forces of the Gogny type connected with different nuclear matter incompressibilities are used and the ensuing sensitivity of the flow is studied. The question whether the flow provides information on out-of-equilibrium matter properties is investigated.

A formulation of the quantum-mechanical nonrelativistic N-body problem is derived using as guiding principle the dynamical evolution of two-cluster partitions of the N particles during the scattering process. This concept is realized by first making a certain choice for the basic subcluster-exchange potentials and then requiring consistency at all subsystem levels to generate the detailed structure. A decoupling is performed which divides the two-cluster partitions into primary and secondary ones, thus leading to a generalized optical potential-type formulation which makes the description of the reaction mechanisms very detailed and transparent and allows for a convenient graphical visualization. The resulting effective two-body equations of Lippmann-Schwinger form take full account of the Pauli principle and involve as input only physical subsystem transition amplitudes. The present approach may be understood as an off-shell transformation of the corresponding Alt-Grassberger-Sandhas N-body equations which eliminates some off-shell dependence of the latter. As a direct consequence of the compound nature of spectator clusters, the final equations turn out to be four-dimensional, involving one off-shell energy and one vector momentum as integration variables. Implications of this finding for a possible relativistic generalization are discussed.

In this paper we discuss inelastic breakup, which is one of the direct components of the inclusive energy spectra for transfer to the continuum reactions. There is inelastic breakup when a nucleon is emitted by the projectile without being absorbed by the target but at the same time the target undergoes an inelastic excitation because of the final-state interaction. We estimate the inelastic breakup from the imaginary part of the nucleon-nucleus optical potential. The basic assumption is that inelastic processes give the major contribution to the surface part of the absorptive potential. Our approach allows inelastic breakup to be distinguished from elastic breakup in which the target remains in its ground state and from other types of absorptive effects like transfer to single particle and/or compound nucleus resonances and we discuss the energy evolution of the various processes.

We develop a simple method of treating spin effects in the frame of algebraic scattering theory and apply it to the system ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{65}$Cu at ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=44.77 MeV.

Microscopic coupled-channels calculations for the ground-state rotational band of ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ are performed using the folding model and density-dependent effective interactions. Transition densities are obtained either from the shell model or from fits to electron scattering data. The quadrupole contribution to elastic scattering enhances the cross section and damps the analyzing power for momentum transfers larger than about 1.2 ${\mathrm{fm}}^{\mathrm{-}1}$. Channel coupling is more important for the 7/$2^{\mathrm{-}}$ than for the 5/$2^{\mathrm{-}}$ state and roughly follows the energy dependence of the interaction strength. Comparisons are made between calculations using either theoretical effective interactions or empirical effective interactions previously fitted to data for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ or ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. The results demonstrate that medium modifications are quite important and well described by the local density approximation. Therefore, the effective interaction depends primarily upon local density and is almost independent of nucleus, state, or deformation.

We apply the technique of multifractals to study the dynamical properties of the particles produced in semicentral collisions of ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ ions at 200A GeV, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ions at 200A and 60A GeV, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ ions at 14.5A GeV, ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ ions at 140A and 11A GeV and a proton beam at 800 GeV in nuclear emulsion. A power-law behavior has been observed in the data. The dynamical fluctuations in multiplicity distributions are characterized by smooth multifractal spectra f(${\mathrm{\alpha }}_{\mathit{q}}$). The results agree quite well with the predictions of a multistring model.

Central rapidity Λ production has been measured in sulfur collisions with Cu, Ag, and Pb at 200 GeV/c per nucleon. Lambdas produced in these collisions were identified by their charged decays recorded by a time projection chamber. The Λ yields are compared as a function of target mass. For each target, the yields are reported as a function of Λ transverse kinetic energy and zero degree energy (a measure of collision centrality). In each system, the data exceed predictions of the venus size-2(4.02) model of sulfur-nucleus collisions. The observed excesses show no obvious variation with collision centrality from moderate to highly central collisions.

The nuclear-matter equation of state is studied with a momentum-dependent effective interaction. The incompressibility and the zero-temperature optical potential are calculated analytically. The momentum distribution of nucleons is examined and the effect of the momentum dependence on pion-production rates is illustrated. The phase transition to a quark-gluon plasma, described by a bag-model equation of state, is studied in an approximation suitable for infinite nuclear matter.

Distributions of transverse energy, forward energy, and ${\mathit{dE}}_{\mathit{T}}$/dη from 60A GeV and 200A GeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{induced}$ and 200A GeV ${}_{}{}^{32}{}_{}{}^{}\mathrm{induced}$ nuclear collision with Al, Cu, Ag, and Au are calculated by a high energy nuclear collision model and compared to recent experimental data from the WA80 Collaboration at CERN. The high energy nuclear collision Monte Carlo model which is based on the concept of independent multiple nucleon-nucleon collisions, describes the experimental data at forward-rapidity and midrapidity well.

By making use of a mapping procedure recently proposed, we construct the nucleon image of the one-body quark density operator in the framework of the nonrelativistic quark model of the nucleons. We evaluate the expectation value of this operator in the ground state of the doubly magic nuclei ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ described within the nuclear shell model. We analyze the role of quark exchanges between nucleons. We also investigate the effect on the quark density of short-range correlations in the nuclear wave functions as well as of variations in the nucleon size.

An expression for the measured nuclear transparency in quasielastic high energy (p,2p) reactions is derived in a semiclassical approach which includes the multiple elastic scattering (MS) of the incoming and outgoing protons. It is shown that if one ignores MS in the analysis of the experimental data, an artificial energy dependence of the transparency will be observed. The transparency increases with incident momentum, but its absolute value is less than that predicted by the conventional semiclassical (Glauber) picture. We demonstrate that it is sufficient to apply a simple selection of data, based on an energy resolution of approximately 100 MeV, to avoid the artifact of the neglected MS. We also show that the MS cannot explain the absolute increase of nuclear transparency observed in (p,2p) large angle data, nor can it account for its incident momentum dependence.

Parity nonconservation (PNC) was studied for 16 p-wave resonances in ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ by measuring the helicity dependence of the total cross section for epithermal neutrons scattered from ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. A statistical analysis yields a root-mean-square PNC matrix element M=0.${56}_{\mathrm{-}0.20}^{+0.41\mathrm{}}$ meV, which corresponds to a spreading width of ${\mathrm{\Gamma }}^{\mathrm{PV}}$=0.9×${10}^{\mathrm{-}7}$ eV. Under plausible assumptions this gives a value of 4×${10}^{\mathrm{-}7}$ for ‖${\mathrm{\alpha }}_{\mathit{p}}$‖, the ratio of strengths of the P-odd and P-even effective nucleon-nucleon interactions.

Parity nonconserving (PNC) longitudinal analyzing powers were measured for 23 p-wave neutron resonances in ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$. Seven resonances show effects of greater than 2.4σ statistical significance—the largest sample yet measured in a single nucleus. All seven analyzing powers have positive sign. Strong sign correlations are not a feature of the conventional statistical model of parity mixing between compound nuclear states. The asymmetry was expressed as a sum of two terms: a constant asymmetry and a fluctuating asymmetry. With this ansatz the root-mean-square PNC matrix element M=1.$2_{\mathrm{-}0.4}^{+0.5\mathrm{}}$ meV, which corresponds to a spreading width of ${\mathrm{\Gamma }}^{\mathrm{PV}}$=6×${10}^{\mathrm{-}7}$ eV.

We present a calculation of first-forbidden β-decay transitions in the lead region using relativistic mean-field and relativistic Hartree approximations to a quantum hydrodynamic model of Serot and Walecka. A formalism for the response of the core to a valence particle or hole in the case of weak transitions is developed and studied for the π- and ρ-meson fields present in the model. Two applications are shown for which the mean-field results show a sizable enhancement of the matrix element. This enhancement is partly quenched by the inclusion of the vacuum corrections. The core response for these cases turns out to be negligible in the long wavelength limit. Altogether, it is concluded that the relativistic effects discriminate against nonrelativistic calculations but, however, are not enough to account for the recently reported discrepancy between shell model analysis of beta-decay rates and the (nonrelativistic) impulse approximation and meson-exchange-current calculations.