Inclusive double differential neutron induced ${\mathrm{\pi }}^{+}$ and ${\mathrm{\pi }}^{\mathrm{-}}$ production cross sections were measured as a function of neutron energy for four targets: C, Al, Cu, and W. The neutron energy range was 200–600 MeV and the pion angular range was 25°–125° (laboratory). The charge, scattering angle, and energy of the pions were measured. The measurements are compared with intranuclear cascade (INC) calculations and a previous experiment that measured the sum of the ${\mathrm{\pi }}^{+}$ and ${\mathrm{\pi }}^{\mathrm{-}}$ cross sections. Our data agree with the measured data, but the INC calculations give only moderate agreement both with the double differential cross sections as well as with angular distributions and total cross sections as a function of neutron energy. The ratio ${\mathrm{\pi }}^{\mathrm{-}}$:${\mathrm{\pi }}^{+}$ was found to increase rapidly with decreasing neutron energy and the pion production was found to increase approximately as ${\mathit{A}}^{2/3}$ for the different targets.

The quantum molecular dynamics method is used to study the details of reaction mechanisms and transitions among them in light heavy-ion systems. The outline of evolution of reaction mechanism is discussed by studying the incident-energy dependence of the fragment mass distribution in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{16}$O system. The calculated total cross sections of medium-mass fragments in the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$${+}^{12}$C system agree with data. The analysis of time variation of kinetic energies of nucleons relative to their parent clusters is shown to be very useful to clarify the reaction mechanisms. The calculated double differential cross sections of light fragments in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{12}$C system show good agreement with experiments. The average of cluster internal energies is found to saturate with regard to the increase of incident energy.

A method is proposed to account for the emission of light particles in heavy-ion fusion reactions using the Boltzmann master equation approach. The method consists in a simple phase space calculation which allows one to estimate the formation probability of a cluster for a given energy distribution of the nucleons. The emission probability of the clusters at each stage of the equilibration cascade is calculated and the changes of the occupation probabilities of the nucleon energy states due to these emissions is accounted for by a new depletion term in the set of master equations. The calculated spectra of deuterons, tritons, and α particles reproduce satisfactorily the exclusive spectra measured in ${}_{}{}^{16}{}_{}{}^{}\mathrm{-}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{Ag}$ fusion at 30 MeV/nucleon incident energy. The same model is used to predict the emission of clusters in nucleon-induced reactions with satisfactory results.

Dynamical evolution of the nucleus-nucleus collisions in the Fermi energy domain is followed from the point of interaction to the evaporation residues on an event-by-event basis by a Monte Carlo simulation technique. The complete reaction process comprises two phases: (i) the preequilibrium phase and (ii) the evaporation phase. The initial preequilibrium phase leads to the formation of an incompletely fused composite that, assumed to be thermally equilibrated, subsequently decays leading to final residues. The calculations are parameter free. The calculated inclusive residue charge distribution, exclusive proton and α-particle spectra, and other physical observables for the reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{24}$Mg and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{13}$C at 1100 MeV are compared with the respective experimental data. The theoretical predictions are found to be in good agreement with the experimental results.

A new symmetric three-body coupling model has been developed for the description of the final state of knockout reactions. This model provides an exact description of the three-body final state when either one or both of the two distorting optical potentials vanish. Such a model gives a good description of the situation present in the knockout reactions in the extreme peripheral region, where at least one of the distorting optical potentials is ineffective. Comparison between the predictions of this model and the conventional kinematic coupling model for the 140 MeV ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(α,α’p)n reaction and the 90 MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(α,2α${)}^{12}$C reaction are illustrative of the conclusions which could be drawn from cluster knockout reaction analyses.

Statistical model calculations, employing optical model transmission coefficients for particle emission, have been able to describe in a satisfactory way n, p, d, t, and α emission properties of compound nuclei at excitation energies below 100 MeV. Recent experimental data have shown that the same model systematically overpredicts the deuteron and triton yields observed at higher excitation energies up to 405 MeV. The predictions of the statistical model with transmission coefficients derived from an ingoing-wave boundary condition and a direct reaction approach to fusion method are discussed. It is shown that a description of the deuteron and triton data is possible, provided that the corresponding inverse cross sections are reduced from the optical model predictions. For deuteron emission in particular, the required reduction is found to be consistent with experimental deuteron fusion cross sections. The breakdown of the traditional approach is attributed to the large percentage of nonfusion components contained in the optical model absorption cross section.

The cross section for the elastic scattering of α particles from ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ at ${\mathit{E}}_{\mathrm{lab}}$=26 MeV/nucleon is calculated. The single-folding potential plus second-order rescattering correction is used as an optical potential. It is found that the angular distribution is farside dominated. The second-order correction, which contains the short-range correlation effects, merely adds to absorption. Comparison to the α${+}^{12}$C system is made.

The general properties of the nucleon-nucleus interaction is studied by considering a nonlocal model, called model K, which is formulated within the framework of the resonating-group method, but with the simplifying assumptions of approximating target-recoil effects and taking into account only the knockon-exchange contribution. The procedure that we follow is to first construct and then examine the internuclear equivalent local potentials corresponding to the nonlocal interaction of model K. Two methods of construction are adopted; these are the Born approximation and the WKB procedure. From the resultant equivalent local potentials, we obtain the following interesting findings: (i) The knockon-exchange process is important especially at lower energies; for example, at 20 MeV, the volume integral of the knockon-exchange potential is equal to 29% of that of the direct potential; (ii) a proper consideration of antisymmetrization alone can already account for about 70% of the energy dependence of the empirically determined internuclear local potential; and (iii) the nucleon-nucleus interaction does not seem to depend sensitively on the excitation energy of the target nucleus.

Two-particle azimuthal correlations are studied in 4.2 GeV/c per nucleon dC, αC, and CC collisions with a propane bubble chamber at JINR Dubna Synchrophasotron. It is found that the azimuthal correlations are different for different pairs of secondary particles, and that they also depend on the mass of the projectiles and the collision centrality. The majority of the observed characteristics can be accounted for by the kinematic correlations calculated from the model of independent nucleon-nucleon collisions. The only exception is the effect of close pairing of like particles considered to be due to the identical particle effect for pion pairs and to short-range strong interactions for proton pairs.

We have searched for examples of nuclear charge pickup by relativistic uranium ions in targets of both uranium and phosphate glass. We find none, which allows us to set an upper limit of 7.7 mb per target atom at the 90% confidence level on the cross section for this process. An extrapolation of the approximately quadratic dependence on projectile charge of the cross section for charge pickup predicts a cross section which would be ∼10 times larger. This breakdown in the scaling can be understood by the propensity of the actinides to fission upon the deposition of sufficient excitation energy.

We report a direct measurement of the final-state energy spectrum in the electromagnetic dissociation of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ into p+ ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ at an energy of 14.6 GeV/nucleon. The final-state energy is obtained through a calculation of the p${\mathrm{-}}^{27}$Al invariant mass in kinematically reconstructed events. The final-state energy spectrum for all targets is peaked near the isovector giant-dipole resonance in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ and the dependence of the magnitude of the cross section on target charge confirms that the excitation is largely electromagnetic. By exploiting the expected scaling behavior on target Z and A, the background from nuclear interactions is evaluated and subtracted, leaving a pure electromagnetic dissociation final-state energy distribution. This distribution is well reproduced by simulated events, in which the photon spectrum calculated in the Weiszäcker-Williams approximation is combined with experimental data on the photonuclear reaction ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$(γ,p) ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, and slight differences are observed only at low final-state energy.

We calculate the production cross sections for kaons and π mesons in a new hadronic fireball model, which includes all hadrons of masses below 1.3 GeV. We find that we are able to reproduce the increase in the K/π ratios in nucleus-nucleus collisions as compared to proton-nucleus collisions, which was experimentally observed by the E802 Collaboration at Brookhaven National Laboratory. In addition, we predict an isospin effect to be visible in these ratios.

Neutral pion condensation in quark matter is investigated including vacuum polarization effects. The vacuum instability is removed by eliminating the Landau ghost from the meson propagators.

The process of electron emission from ∼30 MeV neutrino absorption on carbon, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\nu }_{\mathit{e}}$,${\mathit{e}}^{\mathrm{-}}$${)}^{12}$N, has been observed. The flux-weighted total cross section for the exclusive neutrino-induced nuclear transition ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\nu }_{\mathit{e}}$,${\mathit{e}}^{\mathrm{-}}$${)}^{12}$N(g.s.) is [1.05±0.10(stat)±0.10(syst)]×${10}^{\mathrm{-}41}$ ${\mathrm{cm}}^2$. The measured cross section and angular distribution dσ/dΩ are in agreement with theoretical estimates. The inclusive ${\nu }_{\mathit{e}}$ ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reaction rate, which accounted for the majority of all neutrino interactions observed in this experiment, was determined from a detailed fit of energy and angular distributions for the observed electrons. The inclusive ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\nu }_{\mathit{e}}$,${\mathit{e}}^{\mathrm{-}}$)X cross section is measured to be [1.41±0.23(tot)]×${10}^{\mathrm{-}41}$ ${\mathrm{cm}}^2$. An upper limit for the sum of the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$(${\nu }_{\mathit{e}}$,${\mathit{e}}^{\mathrm{-}}$)X${+}^{27}$Al(${\nu }_{\mathit{e}}$,${\mathit{e}}^{\mathrm{-}}$)X inclusive absorption cross sections is presented.

Based on calculations performed with the continuum random phase approximation model we compare neutrino- and antineutrino-induced reactions on several target nuclei. We find that neutrinos and antineutrinos excite parts of the isovector giant dipole resonance differently, with scattering on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ showing the most noticeable deviations.

The neutron capture cross sections of ${}_{}{}^{122,123,124,125,126}{}_{}{}^{}\mathrm{Te}$ were measured in the energy range from 10 to 200 keV at the Karlsruhe Van de Graaff accelerator using gold as a standard. Neutrons were produced via the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$(p,n${)}^7$Be reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 4π barium fluoride detector. Several sets of measurements were performed under different experimental conditions to study the systematic uncertainties in detail. The cross section ratios σ(Te)/σ(Au) were determined with an overall uncertainty of ∼1%. This is an improvement by about a factor of 5 compared to existing data. Maxwellian-averaged neutron capture cross sections were calculated for thermal energies between kT=10 and 100 keV by normalizing the cross section shape up to 600 keV neutron energy reported in literature to the present data. These stellar cross sections were used in an s process analysis. With the classical approach the abundances of the three s only isotopes ${}_{}{}^{122,123,124}{}_{}{}^{}\mathrm{Te}$ could be reproduced within the experimental uncertainties of ∼1%. The accuracy of the present data also allowed us to derive constraints for the existing stellar models with respect to the effective neutron density. Furthermore, the p process abundances for the tellurium isotopes are discussed.

The currently favored s process scenario of helium shell burning in low mass stars involves a range of thermal energies from kT=12 to 25 keV with most of the neutron exposure taking place at low temperatures. Therefore, differential cross sections are required down to the region of resolved resonances for the reliable determination of the Maxwellian-averaged cross sections typical of the stellar plasma. This work deals with the neutron capture cross sections of the important s only isotopes ${}_{}{}^{122}{}_{}{}^{}\mathrm{Te}$, ${}_{}{}^{123}{}_{}{}^{}\mathrm{Te}$, and ${}_{}{}^{124}{}_{}{}^{}\mathrm{Te}$, which were measured between 1 and 60 keV neutron energy with a setup of Moxon-Rae detectors. The systematic uncertainties achieved in this experiment are ∼5%, but statistical uncertainties are smaller than 2%. In addition to the Moxon-Rae detectors, the setup includes a ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ glass detector which could be used to determine the total neutron cross sections simultaneously. These results represent the first set of experimental data in this energy range.

High resolution electron scattering measurements at 180° have been performed on ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ at low momentum transfer. Transverse form factors have been extracted for transitions to the 3.68 MeV 3/$2^{\mathrm{-}}$ and 3.85 MeV 5/$2^{+}$ states, with emphasis on mapping the low-q behavior of the magnetic contributions to these form factors. The magnetic transition strengths to the 1/$2^{\mathrm{-}}$ ground state have been determined. The results are compared to one-body density matrix element calculations using both Woods-Saxon and harmonic oscillator wave functions. The data are in good agreement with the parameters derived for these wave functions from previous measurements taken at higher momentum transfer.

The low-lying levels in ${}_{}{}^{109}{}_{}{}^{}\mathrm{Cd}$ were excited via the (p,nγ) reaction. Angular distributions of deexcitated gamma rays were studied at 4.2 MeV proton energy to resolve the ambiguity in the spin values for the levels at 721.3, 891.1, 997.3, and 1133.6 keV excitation energies.

Coupled channels calculations that simultaneously predict elastic scattering and fusion reaction cross sections are compared with the corresponding available measurements for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{63,65}$Cu collisions. The calculations can reproduce the main features of the fusion and elastic scattering data sets but only separately by using significantly different ion-ion potentials.