In the framework of the Brueckner-Bethe-Goldstone theory, we determine a fully microscopic equation of state for asymmetric and $\beta$-stable nuclear matter containing ${\Sigma }^{-}$ and $\Lambda$ hyperons. We use the Paris and the new Argonne ${\mathrm{Av}}_{18}$ two-body nucleon interaction, whereas the nucleon-hyperon interaction is described by the Njimegen soft-core model. We stress the role played by the three-body nucleon interaction, which produces a strong repulsion at high densities. This enhances enormously the hyperon population, and produces a strong softening of the equation of state, which turns out almost independent on the nucleon-nucleon interaction. We use the new equation of state in order to calculate the structure of static neutron stars. We obtain a maximum mass configuration with $M_{\max }=1.26\mathrm{}$ (1.22) when the Paris ${(Av}_{18})$ nucleon potential is adopted. Central densities are about 10 times normal nuclear matter density. Stellar rotations, treated within a perturbative approach, increase the value of the limiting mass by about 12%.

We investigate the elastic scattering cross section of cold dark matter candidates, i.e., lightest supersymmetric particles (LSP), with light nuclei ${(}^{19}\mathrm{F},$ ${}^{23}\mathrm{Na},$ and ${}^{29}\mathrm{Si}).\mathrm{}$ These nuclei are promising targets of direct detection for such cold dark matter. We pay special attention to the spin dependence of the differential event rate. Our calculations are performed in the $s-d$ shell model space with the Wilthental interaction. We also examine the momentum transfer dependence of the differential cross section.

Exclusive measurements of light-charged-particle ${(}^1\mathrm{H},{}^2\mathrm{H},$ and ${}^4\mathrm{He})$ energy spectra, angular distributions, and emission multiplicities are reported for the two reactions ${}^{40}\mathrm{Ar}{+}^{27}\mathrm{Al}$ and ${}^{55}\mathrm{Mn}{+}^{12}\mathrm{C}$ at a matched excitation energy of 127 MeV. Comparisons are made with statistical model predictions for the evaporative processes in these reactions, which can be characterized as emissions from rotational-energy-dominated systems. The model simulations do well in reproducing a broad range of angular distribution data and the ${}^4\mathrm{He}{/}^1\mathrm{H}$ cross-section ratio, using spin distributions derived from fusion cross-section systematics. The same model parameters, however, predict particle energy spectra and coincidence cross sections which are inconsistent with the measurements for both reactions. These results support previous conclusions from model comparisons with inclusive data, and suggest fundamental flaws in the statistical model as applied to light-mass, high-spin, nuclear systems.

We study kaonic atoms over the periodic table using a kaon self-energy in the nuclear medium derived from the SU(3) chiral unitary model. This model is quite successful in reproducing the scattering amplitude of meson meson and the strangeness $S=-1$ meson baryon reactions. In particular the properties of the $\Lambda \mathrm{}\left(1405\right)\mathrm{}$ resonance are well reproduced. In the nuclear medium the properties of this resonance are appreciably modified, and consequently the kaon nucleon scattering amplitudes, leading to an attractive kaon nucleus self-energy for densities higher than ${\rho }_0/25.\mathrm{}$ With this interaction we are able to reproduce shifts and widths of kaonic atoms over the periodic table. We also investigate the region of deeply bound kaonic nuclear states which appear with very large widths in medium and heavy nuclei. Some of the deep atomic states, still unobserved, appear with narrower widths than the separation between levels, which makes them eligible for experimental observation. To this end, we make some estimates of the rates of formation in the ${(K}^{-},\gamma )$ reaction.

The preformation amplitudes for $\alpha$ and ${}^{10}\mathrm{Be}$ clusters in the cold ternary fission of ${}^{252}\mathrm{Cf}$ are estimated within a microscopic model starting from single particle spherical Woods-Saxon wave functions and with a large space BCS-type configuration mixing. The resulting position of the maximum of cluster preformation probability is situated in the region between the two heavier fragments near the scission point, and approaches the fission axis as the distance between the fragments increases.

We have generalized the extended Thomas-Fermi plus Strutinsky integral (ETFSI) method to include a possible triaxiality of the nuclear shape, and investigated the effect on both ground states and fission barriers. In all the 36 cases that we have studied the effect of the triaxiality on the ground-state binding energy never exceeds 0.7 MeV, which is smaller than the rms error of the ETFSI-1 mass fit. As for the 15 fission barriers that we have studied, the average lowering arising from triaxiality is 0.6 MeV, while the maximal effect is 1.3 MeV, which is smaller than the maximal disagreement between the ETFSI-1 barriers and experiment.

With the help of the variational principle we derive general necessary conditions for the existence of a bound state in few-body systems. The conditions we obtain are used to explain some characteristic qualitative features of nuclear Borromean systems like ${}^6\mathrm{He}.$

Cross sections and differential cross sections of ${}^{39}\mathrm{K}(n,\alpha {)}^{36}\mathrm{Cl}$ at $En=4.5,$ 5.5, and 6.5 MeV, and that of ${}^{40}\mathrm{Ca}(n,\alpha {)}^{37}\mathrm{Ar}$ at $En=5\mathrm{}$ and 6 MeV were measured. These data and other available experimental data were used in optical model calculations which contain a dispersion relation term. One set of parameters for dispersive optical potentials of ${}^{39}\mathrm{K}\mathrm{}(n,n),$ $\mathrm{}(n,p),$ and $(n,\alpha )$ reactions is determined, and subsequently used in the dispersive optical model (DOM) calculations for ${}^{40}\mathrm{Ca}\mathrm{}(n,n),$ $\mathrm{}(n,p),$ and $(n,\alpha )$ reactions. A good description of the experimental data with DOM is achieved, and the results are compared with that of the spherical optical model.

The total neutron cross section of the nucleus ${}^{99}\mathrm{Tc}$ from 3 eV to 150 keV has been measured using the time-of-flight technique at the pulsed white neutron source of the Geel Electron Linear Accelerator (GELINA). Up to 10 keV 659 resonances have been resolved and analyzed using the R-matrix neutron resonance shape fitting program REFIT. We have attempted to make a division of the resonances into s and p waves on the basis of their neutron widths. Information on level spacing and neutron strength function has been derived from the resolved resonances. From 10 to 150 keV the average cross section has been analyzed in terms of average level parameters. The results of the present work are compared to previous work, and to the data from the main existing neutron data libraries.

Cross sections are presented for the ${}^{16}\mathrm{O}(\overrightarrow{\gamma },{\pi }^{-}p)$ reaction at incident photon energies between 290 and 325 MeV. The data are presented for specific proton and pion angles as a function of proton energy, which are compared with calculations in a local distorted wave impulse approximation model. The results are in agreement at most kinematics, although at some kinematics the data and calculations disagree by a factor of 2 or more. These data do not support the conclusion of a large modification to the mass of the $\Delta$ resonance in the nucleus.

The elastic ${}^{17}\mathrm{O}{(}^{16}\mathrm{O}{,}^{16}\mathrm{O}{)}^{17}\mathrm{O}$ ${(5/2\mathrm{}}^{+})$ and inelastic ${}^{17}\mathrm{O}{(}^{16}\mathrm{O}{,}^{16}\mathrm{O}{)}^{17}{\mathrm{O}}^{*}$ ${(1/2\mathrm{}}^{+})$ scatterings are studied with a coupled-reaction-channel three-body model for $E_{\mathrm{}\mathrm{c}.\mathrm{m}.\mathrm{}}$ below 40 MeV. Without any parameter fit, the results agree fairly well with experiment for various deep and shallow ${}^{16}\mathrm{O}{+}^{16}\mathrm{O}$ potentials. In regions where no experimental data are available, the theoretical cross sections are sensitive to the choice of ${}^{16}\mathrm{O}{+}^{16}\mathrm{O}$ potential. The comparison of calculations with exactly phase-equivalent deep and shallow ${}^{16}\mathrm{O}{+}^{16}\mathrm{O}$ potentials deduced from supersymmetric transformations shows that this sensitivity is not related to the presence or absence of Pauli forbidden states. Assuming charge symmetry, we also calculate cross sections for the elastic ${}^{17}\mathrm{F}{(}^{16}\mathrm{O}{,}^{16}\mathrm{O}{)}^{17}\mathrm{F}$ ${(5/2\mathrm{}}^{+})$ and inelastic ${}^{17}\mathrm{F}{(}^{16}\mathrm{O}{,}^{16}\mathrm{O}{)}^{17}{\mathrm{F}}^{*}$ ${(1/2\mathrm{}}^{+})$ scatterings. The elastic cross sections of both mirror collisions display a strong backward rise for $E_{\mathrm{}\mathrm{c}.\mathrm{m}.\mathrm{}}>20\mathrm{}$ MeV. Below 10 MeV, the inelastic ${}^{16}\mathrm{O}{+}^{17}\mathrm{F}$ excitation functions are strongly enhanced by the long range of the ${}^{17}\mathrm{F}$ first excited state.

The spin-averaged electromagnetic polarizabilities of the hyperons $\Lambda$ and $\Sigma$ are calculated within the one-loop approximation by use of the dispersion theory. The photon and meson couplings to hyperons are determined so as to satisfy the large $N_c$ consistency condition. It is shown that in order for the large $N_c$ consistency condition to hold, exotic hyperon states such as ${\Sigma }^{**}$ with $I=2\mathrm{}$ and $J=3/2\mathrm{}$ are required in the calculation of the magnetic polarizability of the $\Sigma$ state.

A polarized proton beam with a large longitudinal polarization component of $0.545\pm 0.005$ (96% of the total polarization) was prepared in a storage ring (IUCF–Cooler). This was achieved by means of spin precession solenoids in two of the six straight sections of the ring. A polarized hydrogen storage cell target internal to the ring was used to measure the longitudinal spin correlation coefficient $A_{\mathrm{zz}}$ in $\mathrm{pp}$ elastic scattering over the laboratory angular range $5.5°$–$43.5°\hspace{0.5em}({\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=11.5\mathrm{}°$–$90°)$ with statistical errors of typically 0.025. The absolute normalization was determined to an accuracy of 2.0% by use of the identity $A_{\mathrm{yy}}-A_{\mathrm{xx}}-A_{\mathrm{zz}}\equiv 1$ at ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=90\mathrm{}°.$ The identity also allows a reduction of the scale factor uncertainty of the previously published analyzing powers and spin correlation coefficients. The results are compared to recent $\mathrm{pp}$ partial wave analyses and $\mathrm{NN}$ potential models.

Breakup cross sections of ${}^8\mathrm{B}$ are analyzed in a two-body structure model, with an inert ${}^7\mathrm{Be}$ core and a loosely bound valence proton. The nuclear induced breakup is calculated in an eikonal approximation, and Coulomb dissociation is calculated to first order. There is a strong correlation within this model between the total $E1\mathrm{}$ strength and the one-proton removal cross section ${\sigma }_{1p}.$ Thus we find that the measured values of ${\sigma }_{1p}$ for a carbon target are consistent with the $E1\mathrm{}$ strength extracted in recent Coulomb dissociation experiments. The predicted ${\sigma }_{1p}$ values on high-$Z$ targets are significantly larger than measured. We discuss how this discrepancy can be reduced by improving the description of Coulomb dissociation.

The theoretical study of cross sections for polarized-target measurements of $\pi \overrightarrow{N}\pi \pi N$ reactions gives evidence that the interplay between the strong contribution from the one-pion exchange (OPE) mechanism and the one from isobar exchanges, which is equally strong within the isobar half-width energy region, must result in nontrivial polarization phenomena. The Monte Carlo simulations for asymmetries in the ${\pi }^{-}{p}^{\uparrow }\to {\pi }^{-}{\pi }^{+}n$ reaction at $P_{\mathrm{lab}}=360\mathrm{}\hspace{0.5em}\mathrm{MeV}/c$ with the use of theoretical amplitudes found as solutions for unpolarized data at $P_{\mathrm{lab}}<500\mathrm{}\hspace{0.5em}\mathrm{MeV}/c$ provide confirmations for a significant effect. The effect is capable of discriminating between the OPE and isobar exchanges and it is sensitive to the OPE parameters in question. This leads to the conclusion that the decisive $\pi \overrightarrow{N}\pi \pi N$ analysis, aiming at a determination of $\pi \pi$-scattering lengths, must combine both unpolarized data and polarization information. The appropriate measurements are shown to be feasible at the already existing CHAOS spectrometer.

We investigate the self-consistency condition (SCC) of mean-field theory in the Walecka model and find that the solutions of the SCC are multiple at high temperature and chemical potential. Using the effective Lagrangian approach, we study medium effects on the $\omega$ meson mass by taking into account vacuum effects. We show that the $\omega$ meson mass decreases with both temperature and chemical potential with a general tendency, while near the critical point several $\omega$ meson masses degenerate due to the multiple solutions of the SCC. We check the validity of the Brown-Rho scaling law in this case. Finally, we calculate the thermodynamic potential and prove that the multiple solutions of the SCC result from a first-order phase transition of nuclear matter in the Walecka model at high temperature and chemical potential.

We test the utility of an effective nucleon $\mathrm{}\left(N\right)\mathrm{}{-}^{12}\mathrm{C}$ profile function in calculating nucleus-${}^{12}\mathrm{C}$ optical phase shift function in the Glauber theory. A calculation of the complete Glauber amplitude is performed by using wave functions for ${}^4\mathrm{He}$ and ${}^6\mathrm{He}$ projectiles, leading to the reaction and elastic differential cross sections in good agreement with experiment. By relating the $N{-}^{12}\mathrm{C}$ profile function to the $\mathrm{NN}$ profile function, we derive a new, simple formula to calculate reaction cross sections which requires only nuclear densities as an input. By applying this formula to various combinations of ${}^4\mathrm{He},$ ${}^6\mathrm{He},$ ${}^9\mathrm{Be},$ ${}^{12}\mathrm{C},$ and ${}^{27}\mathrm{Al},$ we can reproduce cross sections measured at 800 MeV/nucleon to much higher accuracy than the optical limit approximation.

We study the possibility of $\rho$-$\delta$ mixing via N-$N$ excitations in dense nuclear matter. This mixing induces a peak in the dilepton spectra at an invariant mass equal to that of the $\delta .$ We calculate the cross section for dilepton production through the mixing process and we compare its size with that of $\pi$-$\pi$ annihilation. In-medium masses and mixing angles are also calculated.

Transition rates from the ground to selected states in ${}^{19}\mathrm{Ne}$ have been measured by their gamma yield following intermediate-energy radioactive ion beam Coulomb excitation. These are compared to corresponding transitions in ${}^{19}\mathrm{F}$ and to shell model calculations. An upper limit on the cross section of the 4.033 MeV state places a limit on the transition rate and hence on total electromagnetic decay width ${\Gamma }_{\gamma }$ of this state, which is of astrophysical interest. Combining the results with an upper limit on the lifetime of this state and shell model calculations gives an estimate of its width.

Results from a $4\pi$ solid angle measurement of the reaction ${\pi }^{+}{+}^4\mathrm{He}\to \mathrm{ppd}$ at incident pion energies of $T_{{\pi }^{+}}=70,$ 118, 162, 239, and 330 MeV are presented. Integrated cross sections are given for the final states with energetic deuterons $\mathrm{}\left(\mathrm{ppd}\right)\mathrm{}$ and $\mathrm{}\left(\mathrm{pd}\right)p.\mathrm{}$ The differential cross sections are described by a complete set of five independent variables and various other kinematic variables and compared to cascade and phase space models where deuterons were formed by a semiclassical pickup model. The data are investigated for signatures of initial and final state interactions: it is found that more than half of the $\mathrm{}\left(\mathrm{ppd}\right)\mathrm{}$ yield cannot be explained by these mechanisms. The remaining strength is reasonably well reproduced by $3N$ phase space models followed by pickup.