The spin correlation coefficent combinations $A_{\mathrm{xx}}{+A}_{\mathrm{yy}}$ and $A_{\mathrm{xx}}-A_{\mathrm{yy}},$ the spin correlation coefficients $A_{\mathrm{xz}}$ and $A_{\mathrm{zz}},$ and the analyzing power were measured for $\overrightarrow{p}\overrightarrow{p}\to d{\pi }^{+}$ between center-of-mass angles $25°<~\theta <~65°$ at beam energies of 350.5, 375.0, and $400.0\hspace{0.5em}\mathrm{MeV}.$ The experiment was carried out with a polarized internal target and a stored, polarized beam. Nonvertical beam polarization needed for the measurement of $A_{\mathrm{zz}}$ was obtained by the use of solenoidal spin rotators. Near threshold, only a few partial waves contribute, and pion $s$ and $p$ waves dominate with a possible small admixture of $d$ waves. Certain combinations of the observables reported here are a direct measure of these $d$ waves. The $d-\mathrm{wave}$ contributions are found to be negligible even at $400.0\hspace{0.5em}\mathrm{MeV}.$

The quantum mechanical inverse elastic scattering problem is solved with the modified Newton-Sabatier method. A set of $S$ matrix elements calculated from a realistic analytic optical model potential serves as input data. It is demonstrated that the quality of the inversion potential can be improved by including nonphysical $S$ matrix elements to half, quarter, and eighth valued partial waves if the original set does not contain enough information to determine the interaction potential. We demonstrate that results can be very sensitive to the choice of those nonphysical $S$ matrix values both with the analytic potential model and in a real application in which the experimental cross section for the symmetrical scattering system of ${}^{12}\mathrm{C}{+}^{12}\mathrm{C}$ at $E=7.998\mathrm{}\mathrm{MeV}$ is analyzed.

Measurements of ${}^{12}\mathrm{C}{+}^{12}\mathrm{C}$ breakup of ${}^{24}\mathrm{Mg}$ have been performed using targets containing carbon, oxygen, lithium, and beryllium. The excitation energy in ${}^{24}\mathrm{Mg}$ was determined from the relative energy of the correlated ${}^{12}\mathrm{C}$ fragments. The data provide the first evidence for the ${}^{12}\mathrm{C}{+}^{12}\mathrm{C}$ breakup of ${}^{24}\mathrm{Mg}$ populated via the ${}^{16}\mathrm{O}{(}^{24}\mathrm{Mg},$ ${}^{12}{\mathrm{C}}^{12}\mathrm{C}{)}^{16}\mathrm{O}$ reaction.

The direct reconstruction of the proton-proton elastic-scattering complex amplitudes is carried out at 1.8 and 2.1 GeV. Five independent amplitudes both in helicity and transversity frame were obtained by using an extensive set of data measured recently at SATURNE II and by the EDDA (COSY) Collaboration. The real and imaginary parts of the amplitudes are plotted versus different interpolated c.m. angles for both frames. Four distinct sets of solutions exist, one of which is chosen on the basis of minimum ${\chi }^2.$

We study bound states in a model with scalar nucleons interacting via an exchanged scalar meson using the Hamiltonian formalism on the light front. In this approach manifest rotational invariance is broken when the Fock space is truncated. By considering an effective Hamiltonian that takes into account two meson exchanges, we find that this breaking of rotational invariance is decreased from that which occurs when only one meson exchange is included. The best improvement occurs when the states are weakly bound.

The damping of the giant dipole resonance (GDR) in neutron-rich nuclei ${}^{18,24}\mathrm{O},$ ${}^{60}\mathrm{Ca},$ and ${}^{150}\mathrm{Sn}$ is calculated within the phonon damping model (PDM) and compared with those in $\beta -$stable isotopes. The Hartree-Fock single-particle energies obtained employing the SGII interaction are used in calculations. The PDM parameter for the $\mathrm{ph}$-phonon interaction between the levels close to the Fermi surface in exotic nuclei has been chosen to simulate the strong coupling between the GDR phonon and dense incoherent $\mathrm{ph}$ configurations. The results of the calculations show the appearance of a low-lying structure (pigmy resonance) in all exotic nuclei under consideration. The calculations at nonzero temperature show that the GDR in hot medium and heavy neutron-rich nuclei exhibits a similar behavior as those of the hot GDR in stable nuclei. The pigmy resonance is smoothed out with increasing temperature.

We present a systematic study of the kaon to pion multiplicity ratios ${(K}^{+}/{\pi }^{+}$ and $K^{-}/{\pi }^{-})$ in heavy-ion collisions from AGS to RHIC energy using the relativistic quantum molecular dynamics (RQMD) model. The model describes reasonably well the available experimental data on $K^{+}/{\pi }^{+}$ and $K^{-}/{\pi }^{-}.$ Within the model, we find that the strong increase of the ratios with the number of participants is mainly due to hadronic rescattering of produced mesons with ingoing baryons and their resonances. The enhancement of $K/\pi$ in heavy-ion collisions with respect to elementary $p+p$ interactions is larger at AGS than SPS energy, and decreases smoothly with bombarding energy. The total multiplicity ratios at RHIC energy are predicted by RQMD to be $K^{+}/{\pi }^{+}=0.19\mathrm{}$ and $K^{-}/{\pi }^{-}=\mathrm{0.15.}\mathrm{}$

The decay of ${}^{77}{\mathrm{Ge}}^m$ (52.9 s) populating the levels of ${}^{77}\mathrm{As}$ has been reinvestigated by measuring $\gamma$-ray singles spectra as a function of time with an HPGe detector. 13 new $\gamma$ rays are assigned to the decay of ${}^{77}{\mathrm{Ge}}^m$ and three new levels are added to the presently accepted level scheme of ${}^{77}\mathrm{As}$ at the following energies: 503.89, 1604.686, and 1676.49 keV. From $\gamma$-ray intensity measurements and $\log \mathrm{ft}$ values determined in this work—combined with previously reported results—tentative $J^{\pi }$ assignments have been made for the new levels proposed.

The interaction between bi-fermionic and bosonic degrees of freedom is described by using an effective Hamiltonian inspired in QCD. The Dyson boson mapping technique is utilized in conjunction with a coherent state basis to construct energy landscapes in a multiparametric space. The appearance of fermionic and bosonic condensates is studied by minimizing the potential energy surface. The relationship between the domains of fermion and boson condensates and the order parameters of the model is discussed.

The contributions of short-range nucleon-nucleon $\mathrm{}\left(\mathrm{NN}\right)\mathrm{}$ correlations, meson exchange current (MEC) terms, and the influence of $\Delta$ isobar excitations (isobaric currents) on exclusive two-nucleon knockout reactions induced by electron scattering are investigated. The nuclear structure functions are evaluated for nuclear matter. Realistic $\mathrm{NN}$ interactions derived in the framework of a one-boson-exchange model are employed to evaluate the effects of correlations and MEC in a consistent way. The correlations are determined by solving the Bethe-Goldstone equation. This yields significant contributions to the structure functions $W_L$ and $W_T$ of the ${(e,e}^{\prime }pn)$ and ${(e,e}^{\prime }pp)$ reactions. These contributions compete with MEC corrections originating from the $\pi$ and $\rho$ exchange terms of the same interaction. Special attention is paid to the so-called “superparallel” kinematics at momentum transfers which can be measured, e.g., at MAMI in Mainz.

The effects of color screening on the hadronization of a parton plasma into a hadron gas are examined at the energies of the Relativistic Heavy Ion Collider. It is found to have the tendency to prevent hadronization, therefore delaying the conversion of the partons into a hadron gas. Because of the continual expansion, the resulting hadron gas number densities are lower when screening is included. This should reduce the hadronic noise to genuine signals of the quark-gluon plasma. In this sense, color screening is favorable and should be included in numerical models. In any case, we advocate that numerical models should allow the confining forces and color screening to act on each other so as to undergo the phase transition in a natural way. Hadronization is also shown to seriously disrupt parton equilibration and is yet another reason why full parton chemical equilibration should not be expected.

Modifications to the nucleon electric polarizability induced by pion and sigma exchange in the $q-q$ potentials are studied by means of sum rule techniques within a nonrelativistic quark model. Contributions from meson exchange interactions are found to be small and in general reduce the quark core polarizability for a number of hybrid and one-boson-exchange $q-q$ models. These results can be explained by the constraints that the baryonic spectrum impose on the short-range behavior of the mesonic interactions.

The energy shift between the level densities of the even-odd and even-even isotopes ${}^{161,162}\mathrm{Dy}$ and ${}^{171,172}\mathrm{Yb}$ is measured as a function of excitation energy. The results are compared with predictions from various semiempirical models. The energy shift procedure works well for excitation energies between 3.5 and 7 MeV in the even-even nucleus, yielding a relative energy shift close to the experimental pairing gap parameter $\Delta .$

Five primary electric-dipole transitions in ${}^{31}\mathrm{Si}$ account for the bulk $(\sim 98\%)$ of the total thermal-neutron capture cross section $(107\mathrm{}\pm 3\hspace{0.5em}\mathrm{mb})$ of ${}^{30}\mathrm{Si}.$ We have recalculated the partial cross sections for these transitions using direct-capture theory and reliable spectroscopic factors for the $\mathrm{}(d,p)\mathrm{}$ reaction, which have become available recently. There is good agreement now between theory and experiment.

The excitation function for the ${}^{233}\mathrm{U}{(}^3\mathrm{He}{,4n)}^{232}\mathrm{Pu}$ reaction was measured. The maximum production cross section is $6.2\pm 1.5\mu \mathrm{b}$ at $32.5\pm 2.2\mathrm{MeV}.$ The plutonium fraction was chemically separated from interfering activities. The ${}^{232}\mathrm{Pu}$ half-life was determined to be $33.1\pm 0.8\min$ using the interference-free data obtained from α-α correlations of daughter activities in equilibrium with the ${}^{232}\mathrm{Pu}$ decay.

The ensemble of charged isotropically emitted ejectiles is studied for central collisions of $\left(17\mathrm{}-115\right)A$ MeV ${}^{40}\mathrm{Ar}\mathrm{}+\mathrm{}\mathrm{Cu},$ Ag, Au. Measurements of average multiplicities, spectral slopes, and masses of the heaviest fragments are compared to statistical models for multifragmentation or sequential evaporation. The multifragmentation models predict much more complete nuclear disassembly than is observed. The evaporation model reproduces the data much more closely except for the spectra of $Z=1\mathrm{}$ ejectiles. The kinetic energies of $Z=1\mathrm{}$ and 2 ejectiles are much less than found for $1A$ GeV ${}^{197}\mathrm{Au}{+}^{12}\mathrm{C}$ for similar energy depositions. Entrance channel dynamics seem to affect the isotropic emission ensembles, often taken to define an equilibrated emission source.

Nuclear disassembly into light and intermediate mass ejectiles is searched for in ${}^{40}\mathrm{Ar}\mathrm{}+\mathrm{}\mathrm{Cu},$ Ag, Au reactions of $17-115A$ MeV. Distributions in fragment mass versus velocity show that such nuclear disassembly does occur for $65-115A$ MeV. However, it is very rare, with much less abundance than reactions leading to a massive residual nucleus.

Radiative capture of the $K^{-}$ by the deuteron is examined as a reaction for measurement of $\Lambda$-neutron scattering lengths. Using the final-state interaction, analogous to measurements of the radiative capture of pions by deuterium, the scattering lengths of both the triplet and singlet $\Lambda$-$n$ interaction can be inferred. The problem of the separation of these two fundamental parameters without and with spin information in the experiment is addressed. It is shown that a measurement of the deviation of the vector deuteron polarization asymmetry from -1 provides a direct determination of the difference of the singlet and triplet scattering lengths.

We study the nuclear isoscalar monopole and dipole compression modes in nuclei within the fluid dynamic approach (FDA) with and without the effect of relaxation. For a wide region of the medium and heavy nuclei, the FDA predicts that the isoscalar giant monopole resonance (ISGMR) and the isoscalar giant dipole resonance (ISGDR) exhaust about 90% of the corresponding model-independent sum rules. In the case of neglecting the effect of relaxation, the FDA, when adjusted to reproduce the centroid energy $E0\mathrm{}$ of the ISGMR, results with centroid energy $E1\mathrm{}$ of the ISGDR which is in agreement with the predictions of the self-consistent Hartree-Fock random-phase approximation calculations and the scaling model but significantly larger than the experimental value. We also show that the FDA leads to the correct hydrodynamic limit for the ratio ${\mathrm{}(E1/E0\mathrm{})\mathrm{}}_{\mathrm{FDA}}.$ We find that the ratio ${\mathrm{}(E1/E0\mathrm{})\mathrm{}}_{\mathrm{FDA}}$ depends on the relaxation time and approaches the preliminary experimental value ${\mathrm{}(E1/E0\mathrm{})\mathrm{}}_{\exp }=1.5\mathrm{}\pm 0.1$ in a short relaxation time limit.

Excited states in ${}^{232}\mathrm{Th}$ were populated by Coulomb excitation with $80\mathrm{MeV}$ ${}^{16}\mathrm{O}$ ions. Gamma-gamma coincidences were detected with the detector array YRAST Ball. The one-phonon quadrupole and octupole vibrations are most strongly excited. These vibrations are in ${}^{232}\mathrm{Th},$ particularly favorable cases for a study of their couplings, due to the small energy spacings of the $\beta$ and $\gamma$ bands and the $K^{\pi }{=1\mathrm{}}^{-}$ and $2^{-}$ bands, respectively. The need for additional experimental information on the $\gamma$-ray intensities and the location of members of the octupole-vibrational bands is emphasized. The higher-lying $K^{\pi }{=0\mathrm{}}^{+}$ bands with bandheads at 1079 and $1352\mathrm{keV}$ proposed previously are observed and some conflicting properties of these bands are discussed. The interpretation of the $1352\mathrm{keV}$ $0^{+}$ band as two-octupole-phonon vibration is not supported by our data. A level at $1054\mathrm{keV},$ previously assigned as $2^{+}$ or $2^{-}$ level, is tentatively proposed to be the bandhead of a second-excited $K^{\pi }{=2\mathrm{}}^{+}$ band. Our $\gamma \gamma$ coincidence data establish that the unusually enhanced $E2\mathrm{}$ transitions from a $2^{+}$ level at $1554\mathrm{keV}$ to members of the $\beta$ and $\gamma$ bands proposed previously do not exist.