The (n,p) reaction has been studied on the nuclei ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$ and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$ at an energy of 198 MeV. Spectra were measured at laboratory angles of 0°, 4°, 8°, 12°, 16°, and 20° up to an excitation energy of 35 MeV in the final nuclei ${}_{}{}^{51}{}_{}{}^{}\mathrm{Ti}$ and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Fe}$. A multipole analysis of the data up to 30 MeV was carried out to identify Gamow-Teller (ΔL=0,Δ${\mathit{J}}^{\mathrm{\pi }}$=$1^{+}$) and spin dipole (ΔL=1,Δ${\mathit{J}}^{\mathrm{\pi }}$=$0^{\mathrm{-}}$,$1^{\mathrm{-}}$,$2^{\mathrm{-}}$) strengths. GT strength is concentrated in a resonance with centroid energy of 5.2 MeV in ${}_{}{}^{51}{}_{}{}^{}\mathrm{Ti}$ and 4.1 MeV in ${}_{}{}^{59}{}_{}{}^{}\mathrm{Fe}$. The spin-dipole strength appears as a broad resonance with centroid energy about 16 MeV in both nuclei. Shell model calculations of the GT strength reproduce the energy distribution reasonably well, but the calculated strength exceeds the measurement by a factor of about four.

The ${(}^3$He,t) charge-exchange reaction has been studied at E${(}^3$He)=200 MeV and angles near 0° on targets of ${}_{}{}^{117}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$. Fragmentation of the giant Gamow-Teller resonance into separate components of the particle-hole type has been observed in good agreement with theoretical predictions. These components are connected with what is usually referred to in the literature as direct-, core-polarization-, and back-spin-flip Gamow-Teller strength. The observed cross sections near θ=0° suggest contributions from the isovector spin-flip interaction as well as the isovector tensor interaction. A theoretically predicted configuration splitting of the main Gamow-Teller component into two components involving the 1${\mathit{h}}_{11/2}$ neutron orbital could not uniquely be identified. The data are compatible, though, with such a splitting since the observed widths of the main Gamow-Teller components in ${}_{}{}^{117}{}_{}{}^{}\mathrm{Sb}$ and ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sb}$ exceed the predicted splittings.

One neutron transfer cross sections in the systems ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$${+}^{144}$Sm and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$+ ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$ have been measured at energies close to the Coulomb barrier. Mass and charge identification was achieved using characteristic x rays. Transfer probabilities were analyzed by considering barrier penetration mechanisms. Possible enhancement effects due to permanent quadrupole deformations are investigated and compared with the experimental results.

γ-ray yields in the energy range ∼5–35 MeV have been measured in the reactions α${+}^{197}$Au and ${}_{}{}^{159}{}_{}{}^{}\mathrm{Tb}$ at ${\mathit{E}}_{\mathrm{\alpha }}$=40 MeV and α${+}^{197}$Au, ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Ag}$, and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$ at ${\mathit{E}}_{\mathrm{\alpha }}$=50 MeV at ${\mathrm{\theta }}_{\gamma }$=90°. Angular distribution measurements have been carried out for the heaviest and the lightest target at ${\mathit{E}}_{\mathrm{\alpha }}$=50 MeV. A reasonably good agreement with the statistical model calculations is obtained for photon energies up to the giant dipole resonance region. A nonstatistical component is observed at higher γ-ray energies for all the systems studied. An attempt to understand the production mechanism of the nonstatistical part is made in terms of the potential bremsstrahlung and the incoherent nucleon-nucleon bremsstrahlung processes. While the calculations give the right order of magnitude of the measured cross sections for the highest γ-ray energies, they fail to reproduce the measured angular distributions and the cross sections in the entire γ-ray energy range.

The present paper identifies unique symmetry properties of the d→+d→d+p+n breakup reaction that make it an excellent probe for studying charge-symmetry breaking. Measurements were made for two configurations of the ejected particles in the breakup reaction to obtain values of the spin observables ${\mathit{A}}_{\mathit{y}}$, ${\mathit{A}}_{\mathit{y}\mathit{y}}$, and ${\mathit{A}}_{\mathit{z}\mathit{z}}$. These observables are compared for the mirror reactions ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d→,dp)n and ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d→,dn)p for the two angle pairs (${\mathrm{\theta }}_{\mathit{d}}$,${\mathrm{\phi }}_{\mathit{d}}$,${\mathrm{\theta }}_{\mathit{N}}$,${\mathrm{\phi }}_{\mathit{N}}$)=(17.0°,0°,17.0°,180°) and (17.0°,0°,34.5°,180°) for an incident deutron energy of 12 MeV. In addition, spin observables for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d→,pn)d reaction at ${\mathrm{\theta }}_{\mathit{p}}$=${\mathrm{\theta }}_{\mathit{n}}$ and ${\mathrm{\phi }}_{\mathit{p}}$=${\mathrm{\phi }}_{\mathit{n}}$+180° are shown to provide a particularly good test of charge symmetry. Our ${\mathit{A}}_{\mathit{y}}$, ${\mathit{A}}_{\mathit{y}\mathit{y}}$, and ${\mathit{A}}_{\mathit{z}\mathit{z}}$ data for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d→,pn)d reaction at (${\mathrm{\theta }}_{\mathit{p}}$,${\mathrm{\phi }}_{\mathit{p}}$,${\mathrm{\theta }}_{\mathit{n}}$,${\mathrm{\phi }}_{\mathit{n}}$)=(17.0°,0°,17.0°,180°) are used to illustrate this latter point. Of the ten charge-symmetric sets of observables measured, two were found to differ by 2.5 standard deviations.

Large and small angle correlation measurements are reported for ${}_{}{}^1{}_{}{}^{}\mathrm{-}_{}^1{}_{}{}^{}$H, ${}_{}{}^4{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He, and ${}_{}{}^2{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He pairs from 7.8A and 17A MeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{\mathrm{nat}}$Ag. These measurements are interpreted with the aid of trajectory calculations designed to simulate evaporationlike emission of particles and fragments. The most important physical parameter needed to fit the correlation function peaks is the fractional yield of unstable fragments ${(}^8$Be or ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$) compared to independently evaporated particles ${(}^4$He${\mathrm{-}}^4$He) or ${(}^2$H${\mathrm{-}}^4$He). In this approach, the peaks in the simulated correlation functions contain essentially no information concerning the space-time extent of the emitter source. Nevertheless, these simulations can account for the data very well.

We use trajectory calculations to analyze small-angle particle-particle correlations for three typical situations: ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{197}$Au (E/A=60 MeV)${\to }^2$H${\mathrm{-}}^2$H pairs and ${}_{}{}^1{}_{}{}^{}\mathrm{-}_{}^1{}_{}{}^{}$H pairs, ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$${+}^{59}$Cu (E/A=30 MeV)→n-n pairs. For the ${}_{}{}^2{}_{}{}^{}\mathrm{-}_{}^2{}_{}{}^{}$H pairs our analysis of the gentle featureless anticorrelations suggests that the major driving force is Coulomb repulsion after a range of average time delays from ≊5×${10}^{\mathrm{-}21}$ s for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ pairs of lower energy to ≊${10}^{\mathrm{-}22}$ s for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ pairs of higher energy. Simulations are used to illustrate the separate dominance of source size and lifetime in the space-time extent of the emitter. For lifetimes ≤${10}^{\mathrm{-}22}$ s the emitter size dominates; for longer lifetimes the time delays become predominant. The peaks at ≊20 MeV/c in the correlation functions for ${}_{}{}^1{}_{}{}^{}\mathrm{-}_{}^1{}_{}{}^{}$H pairs can be accounted for by diproton ejection which decays into protons with a Q value of ≊0.35 MeV and a decay width of ≊1 MeV (or a meanlife of 6×${10}^{\mathrm{-}22}$ s). The positive correlations between neutron pairs can be accounted for by dineutron ejection which decays into neutrons with a near zero Q value and a decay width of ≊0.25 MeV (or a meanlife of ≊2×${10}^{\mathrm{-}21}$ s). If these diproton and dineutron clusters do indeed have a metastable existence, then one should reexamine the notion that their associated small-angle correlations reflect the space-time extent of the emission source.

The existence of entrance channel effects in the decay of ${}_{}{}^{164}{}_{}{}^{}\mathrm{Yb}_{}^{\mathrm{*}}{}_{}{}^{}$, formed at ${\mathit{E}}^{\mathrm{*}}$≊54 MeV in the reactions ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{148}$Sm and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$${+}^{100}$Mo is investigated. Evaporation residue cross sections, entry state γ-ray fold distributions as well as energy and angular distributions of exit channel selected charged particles were obtained for each reaction, using 4π detection systems for both particles and γ rays. In the ${}_{}{}^{64}{}_{}{}^{}\mathrm{induced}$ reaction, the center-of-mass α-particle angular distributions were found to be symmetric around 90° indicating emission from a fully equilibrated compound nucleus. However, the corresponding angular distributions in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{induced}$ reaction show a forward component which exclusively affects the population of the αxn residue channels. The γ-ray fold distributions for the αxn and xn channels show differences depending on the entrance channel as reported previously for similar systems. These differences can be understood in terms of contributions from the equilibrium decay of incompletely fused ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ with ${}_{}{}^{148}{}_{}{}^{}\mathrm{Sm}$ and the mapping of the compound nucleus spin distributions, obtained from realistic fusion models, to the evaporation residue γ-ray fold distributions. It is concluded that the initial population of the compound nucleus is the only reason for the observed differences in the decay of ${}_{}{}^{164}{}_{}{}^{}\mathrm{Yb}_{}^{\mathrm{*}}{}_{}{}^{}$ populated in these reactions.

A consistent description of the formation and decay of ${}_{}{}^{164}{}_{}{}^{}\mathrm{Yb}_{}^{\mathrm{*}}{}_{}{}^{}$ in the fusion of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{148}$Sm and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$${+}^{100}$Mo is presented in a bombarding energy range from near to well below the entrance channel Coulomb barrier. Fusion excitation functions and angular momentum distributions are described well with a recently proposed one-dimensional barrier penetration model with energy-dependent fusion barriers. The main features of fusion and angular momentum distribution data in ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$${+}^{100}$Mo are also reproduced with simplified coupled channel calculations. The statistical model accounts well for the decay of ${}_{}{}^{164}{}_{}{}^{}\mathrm{Yb}_{}^{\mathrm{*}}{}_{}{}^{}$ in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{induced}$ reaction and for most of the data in the ${}_{}{}^{64}{}_{}{}^{}\mathrm{induced}$ reaction. The evaporation residue fractional cross sections as a function of the compound nucleus excitation energy show trends that correlate with the low- and high-spin regions of the compound nucleus angular momentum distributions populated in the two reactions.

A unified model of nuclear reactions taking account of both the compound and preequilibrium nuclear reactions is proposed in terms of a renormalization of the wave functions generated by the optical model potential. The cross sections of the nuclear reactions including preequilibrium processes are formulated, which are especially suited for calculations of cross sections of those nuclear reactions in which the residual nuclei are in discrete levels or isomeric states. The model is used to investigate the reactions ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$(n,2n${)}^{58}$Co and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$(n,2n${)}^{92}$Nb. The results are in good agreement with the experimental data.

An optical potential fragmentation model capable of predicting fragmentation cross sections and fragment momentum distributions is used to analyze recent measurements of 1.65A GeV argon projectiles fragmenting in carbon and potassium-chloride targets obtained with the Heavy Ion Spectrometer System (HISS) at the Lawrence Berkeley Laboratory Bevalac. The theoretical model uses an abrasion-ablation-FSI (frictional spectator interaction) collision formalism to estimate elemental and isotopic production cross sections for comparsion with the measured values. The collision momentum transfer model is incorporated into a Goldhaber formalism to analyze measured transverse and longitudinal distributions of the projectile fragments. Good agreement between theory and experiment is obtained for all observables.

The total cross section of NN→dπ very near threshold is calculated in a simple distorted wave impulse approximation including one-body, pion rescattering, and sigma and omega meson exchange current (MEC) contributions. Calculations with MEC are in good agreement with recent TRIUMF measurements while calculations without MEC are significantly smaller. Thus the MEC mechanism, which was proposed to explain a large enhancement in the pp→pp${\mathrm{\pi }}^0$ cross section, is consistent with NN→dπ data.

Semi-exclusive measurements of high energy photons (${\mathit{E}}_{\gamma }$≥30 MeV) cross sections from the ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$${+}^{197}$Au reaction at 44 MeV/nucleon are analyzed in the framework of the Boltzmann-Nordheim-Vlasov equation with an appropriate semiclassical γ-production probability for the np→n’p’γ elementary process. A detailed analysis on the impact parameter dependence of the γ-ray multiplicity and slope of the energy spectrum is also reported.

We explore the nuclear responses at intermediate energies, particularly in the spin longitudinal σ⋅q and spin transverse σ×q isovector channels, within the continuum random phase approximation framework. We also employ an extension of the standard random phase approximation to account for the spreading width of the single particle states through the inclusion of a complex and energy-dependent nucleon self-energy. The nuclear responses are then used as the basic ingredient to calculate hadronic reactions in the Glauber theory framework. Here both one- and two-step contributions to the multiple scattering series in the quasielastic peak region are taken into account. We find evidence for shell effects in the one-step response and a strong dependence on the momentum regime of the two-step contribution.

The collective flow of nucleons and that of fragments in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C reaction below 150 MeV/nucleon are calculated with the antisymmetrized version of molecular dynamics combined with the statistical decay calculation. The density dependent Gogny force is used as the effective interaction. The calculated balance energy is about 100 MeV/nucleon, which is close to the observed value. Below the balance energy, the absolute value of the fragment flow is larger than that of nucleon flow, which is also in accordance with data. The dependence of the flow on the stochastic collision cross section and its origin are discussed. All the results are naturally understood by introducing the concept of two components of flow: the flow of dynamically emitted nucleons and the flow of the nuclear matter which contributes to both the flow of fragments and the flow of nucleons due to the statistical decay.

A refinement of the first-order optical potential is introduced, consistent with multiple scattering theory and the spectator expansion. A systematic formalism is presented to treat medium contributions associated with the difference between the effective NN t matrix as required by multiple scattering theory and the free NN t matrix. A mean field potential is used to represent the action of the residual (A-1) nucleus upon the struck target nucleon (medium effects). We calculate elastic proton and neutron scattering from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, using the full Bonn interaction and two different mean field potentials taken from realistic and proven nuclear structure models. Results indicate that the medium contributions are insignificant at energies above 300 MeV and provide a significant improvement of the theoretical predictions for laboratory energies between 48 and 200 MeV.

Inclusive and exclusive (π,η) reactions are studied in the framework of a momentum space DWIA model. It is assumed that both reactions are dominated by formation of an N(1535) resonance. Medium corrections for the self-energy of the intermediate ${\mathit{N}}^{\mathrm{*}}$ are taken into account. Cross sections are calculated for (${\mathrm{\pi }}^{+}$,η) inclusive reactions on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and compared with experiment and with existing theoretical calculations. We show that quantitative agreement is obtained with experimental data, assuming this reaction is dominated by quasifree single-nucleon knockout, and using an ${\mathit{N}}^{\mathrm{*}}$ free width of 150 MeV. Differential and total cross sections are calculated for the exclusive reaction ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$(${\mathrm{\pi }}^{+}$,η${)}^{13}$N.

The fragmentation of 1.2 GeV per nucleon ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$ nuclei has been studied. Total charge changing cross sections for H (${\mathrm{CH}}_2$-C), C, and Pb target nuclei, and elemental production cross sections for C and ${\mathrm{CH}}_2$ targets for 1≤ΔZ≤30 have been measured. For heavy projectile fragments, the projected transverse momenta extracted are generally larger than predicted by models based on the internal momenta of nucleons in nuclei. Fits to the heavy fragment momentum distributions yield additional transverse momenta or ‘‘bounce-off’’ which range from ≃500 to 1000 MeV/c.

During the recent commissioning of Au beams at the Brookhaven Alternating Gradient Synchrotron facility, experiment 886 measured production cross sections for ${\mathrm{\pi }}^{\pm }$, ${\mathit{K}}^{\pm }$, p, and p¯ in minimum bias Au+Pt collisions at 11.5A GeV/c. Invariant differential cross sections, ${\mathit{Ed}}^3$σ/${\mathit{dp}}^3$, were measured at several rigidities (p/Z≤1.8 GeV/c) using a 5.7° (fixed-angle) focusing spectrometer. For comparison, particle production was measured in minimum bias Si+Pt collisions at 14.6A GeV/c using the same apparatus and in p+Pt collisions at 12.9 GeV/c using a similar spectrometer at KEK. When normalized to projectile mass, ${\mathit{A}}_{\mathrm{proj}}$, the measured ${\mathrm{\pi }}^{\pm }$ and ${\mathit{K}}^{\pm }$ cross sections are nearly equal for the p+Pt and Si+Pt reactions. In contrast to this behavior, the ${\mathrm{\pi }}^{\mathrm{-}}$ cross section measured in Au+Pt shows a significant excess beyond ${\mathit{A}}_{\mathrm{proj}}$ scaling of the p+Pt measurement. This enhancement suggests collective phenomena contribute significantly to ${\mathrm{\pi }}^{\mathrm{-}}$ production in the larger Au+Pt colliding system.

For the Au+Pt reaction, the ${\mathrm{\pi }}^{+}$ and ${\mathit{K}}^{+}$ yields also exceed ${\mathit{A}}_{\mathrm{proj}}$ scaling of p+Pt collisions. However, little significance can be attributed to these excesses due to larger experimental uncertainties for the positive rigidity Au beam measurements. For antiprotons, the Si+Pt and Au+Pt cross sections fall well below ${\mathit{A}}_{\mathrm{proj}}$ scaling of the p+Pt yields indicating a substantial fraction of the nuclear projectile is ineffective for p¯ production. Comparing with p+Pt multiplicities, the Si+Pt and Au+Pt antiproton yields agree with that expected solely from ‘‘first’’ nucleon-nucleon collisions (i.e., collisions between previously unstruck nucleons). In light of expected p¯ annihilation in the colliding system, such projectile independence is unexpected without additional (projectile dependent) sources of p¯ production. In this case, the data indicate an approximate balance exists between absorption and additional sources of antiprotons. This balance is remarkable given the wide range of projectile mass spanned by these measurements.

A simple hadronic transport model is proposed for studying the rescattering effect of the pion on the K/π ratio in relativistic nucleus-nucleus collisions. The experimental evidences of evolutionary increase of the K/π ratio from p+p to p+Au and to Si+Au at similar incident energy per nucleon are reproduced reasonably. Experimental results of the K/π ratio at CERN energy (200 GeV/nucleon p+W and S+W) comparable with corresponding results at the Brookhaven Alternating Gradient Synchrotron energy (14.6 GeV/nucleon p+Au and Si+Au) are reproduced as well.