Spin observables for elastic p${\mathrm{-}}^{13}$C scattering at 500 and 547 MeV are calculated using a microscopic, momentum-space optical potential in a relativistic Schrödinger equation. Included are the full spin dependences, off-energy-shell kinematics and dynamics, several models for the nuclear structure, exact treatment of the Coulomb force, and spin singlet-triplet mixing. Agreements with data are good for some observables but, in other observables, indicate the need for additional physics.

With an improved Boltzmann-Uehling-Uhlenbeck (BUU) model, we have investigated the reaction dynamics leading to the thermal freeezout for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{124}$Sn collisions. Several criteria are assessed for defining the proper thermal freezout time which separates preequilibrium processes from equilbrium processes. One of these criteria, the time dependence of the thermal excitation energy, provides consistent results for defining the thermal freezeout. The other two criteria, the emission rate of nucleons and the quadrupole moment of the momentum distributions, do not consistently provide accurate freezeout times due to the existence of long time scale collective vibrations. The predicted values for the excitation energies and temperatures, obtained assuming Fermi gas level densities, are quite sensitive to the equation of state and the impact parameter. Surprisingly, both the thermal excitation energies and the residue temperatures, in the limit of a large ensemble of parallel collisions, show little sensitivity to the in-medium nucleon-nucleon cross section.

We are analyzing the hydrodynamics of 200A GeV S+S collisions using a new approach which tries to quantify the uncertainties arising from the specific implementation of the hydrodynamical model. Based on a previous phenomenological analysis we use the global hydrodynamics model to show that the amount of initial flow, or initial energy density, cannot be determined from the hadronic momentum spectra. We additionally find that almost always a sizable transverse flow develops, which causes the system to freeze out, thereby limiting the flow velocity in itself. This freeze-out dominance in turn makes a distinction between a plasma and a hadron resonance gas equation of state very difficult, whereas a pure pion gas can easily be ruled out from present data. To complete the picture we also analyze particle multiplicity data, which suggest that chemical equilibrium is not reached with respect to the strange particles. However, the overpopulation of pions seems to be at most moderate, with a pion chemical potential far away from the Bose divergence.

We show existence of an important difference between strange-particle production in Si-Au collisions at 15A GeV (AGS) and in S-A collisions at 200A GeV (CERN), with A=32 and A=0 (200).

Strange and nonstrange axial-vector meson radiative decays contribute to photon production in hadron gas. One- and two-hadron radiative decay modes of ${\mathit{b}}_1$(1235), ${\mathit{a}}_1$(1260), and ${\mathit{K}}_1$(1270) are studied. At 200 MeV temperature and for a narrow range in photon energies they contribute more to the net thermal photon production rate than πρ→πγ, ππ→ργ, or ρ→ππγ. They provide significant contribution to the rate for photon energies as high as 1.5–2.0 GeV. For higher energies they are less important.

Resonances in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ above the proton threshold have been studied by scattering radioactive ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$ beams off thick polyethylene targets. The isobaric ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$+p scattering was also examined. The analysis of the data under different theoretical approaches is discussed. The energy, total width, spin, and parity of two resonances in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ were assigned unambiguously. The results are compared to those obtained by indirect methods.

We discuss and improve a recent treatment of the absorption of solar neutrinos by ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$, in connection with a proposed solar neutrino detector. With standard-solar-model fluxes and an in-medium value of -1.0 for the axial-vector coupling constant ${\mathit{g}}_{\mathit{A}}$, we obtain a ${}_{}{}^8{}_{}{}^{}\mathrm{neutrino}$ cross section of 3.3×${10}^{\mathrm{-}42}$, about 50% larger than in our previous work, and a ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ cross section that is less certain but nevertheless also larger than before. We then apply the improved techniques to higher incoming energies that obtain at the LAMPF beam dump, where an experiment is underway to finalize a calibraiton of the ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$ with electron neutrinos from muon decay. We find that forbidden operators, which play no role in solar-neutrino absorption, contribute nonnegligibly to the LAMPF cross section, and that the preliminary LAMPF mean value is significantly larger than our prediction.

The neutron emission from the targetlike fragments (TLF) of the inelastic reactions of 157 MeV ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ on ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ has been measured. Neutron energy spectra and multiplicities have been extracted as a function of the dissipated energy for six targetlike fragments mass gates between A=56 and A=70. The comparison between the data and the results of a Monte Carlo simulation based on statistical model calculations with different assumptions on the excitation energy sharing between the reaction partners evidences a dependence from the net mass flow of the evolution of the excitation energy ratios with the energy loss.

The γ rays associated with the decay of ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ga}$ in equilibrium with ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ge}$ have been studied using the 20-element High Energy Resolution Array (HERA) facility. Five new transitions were observed along with the known ones from earlier works. The E2/M1 mixing ratios for two of these new transitions were obtained by γ-γ(θ) techniques.

We have extracted the experimental ${\mathit{J}}_{\mathrm{eff}}$ values from fission fragment angular distributions for the systems of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{232}$Th, ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$${+}^{232}$Th, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{238}$U at near- and sub-barrier energies. The ${\mathit{J}}_0$/${\mathit{J}}_{\mathrm{eff}}$ values for the cases of the above reactions and the heavy-ion reactions with projectiles heavier than A=24 show same systematic trend when plotted as a function of mean-square angular momentum of the fissioning nucleus. This observation leads us to the conjecture that the systematic trend of ${\mathit{J}}_0$/${\mathit{J}}_{\mathrm{eff}}$ bears the signature of non-compound-nucleus fission for the heavy-ion reactions with lighter projectiles at near- and sub-barrier energies.

A perturbative approach to the description of the temperature dependence of Landau damping is developed in the framework of a schematic model based on the su(3) symmetry which presents interesting thermal properties. For T≠0, transition operators of the particle-particle or hole-hole types, which remain inert at T=0, are able to excite the system. Moreover, new modes, which are frozen at T=0, may also be excited. These aspects are in agreement with the experimentally observed broadening of the giant dipole resonance.

Double charge exchange at 292 MeV and 5° populates ${\mathit{T}}_{<}$ states with a cross section (summed up to the double analog state) that is simply related to the double analog cross section.

Antiproton production in Ni+Ni collisions at 1.85 GeV/nucleon is studied in the relativistic Vlasov-Uehling-Uhlenbeck model. The self-energies of the antiproton are determined from the nucleon self-energies by the G-parity transformation. Also, the final-state interactions of the antiproton including both rescattering and annihilation are explicitly treated. With a soft nuclear equation of state, the calculated antiproton momentum spectrum is in good agreement with recent experimental data from the heavy-ion synchrotron at Gesellschaft für Schwerionenforschung Darmstadt. The effect due to the reduced nucleon and antinucleon masses in a medium is found to be more appreciable than in earlier Bevalac experiments with lighter systems and at higher energies.

Nuclear response functions for quasielastic electron scattering are studied in the Δ-resonance region below threshold. We find that the slow falloff below threshold required by the data in the dip region can be understood in a general way that depends only on kinematics and the approximate mass and width of the Δ.

In his recent publication of a NN phase shift analysis below 160 MeV, Henneck reports relatively large values for the mixing parameter ${\mathrm{\epsilon }}_1$. Based on these results, Henneck suggests that the strength of the ρ-meson coupling to the nucleon may be weaker than used in present day NN interactions, like the Paris, Nijmegen, or Bonn potentials. We point out that at low enegies (≲ 100 MeV) there is rather little sensitivity to the strength of the ρ coupling, due to the compensating effect of the second-order tensor term. In order to establish sensitivity, one has to go to energies ≳200 MeV, where the second-order contribution has gone out. As it happens, the ${\mathrm{\epsilon }}_1$ mixing parameter is well determined in the region of energies 200–300 MeV, and there is agreement with the predictions by the Paris and Bonn potentials; the weak-ρ model is about 50% above the data. This and additional considerations in triplet P waves reconfirm that NN scattering requires the strong ρ, consistent with the ππ-NN¯ partial-wave analysis by Höhler and Pietarinen.

Apparent inconsistencies between different formulations of nucleon sum rules at finite density are resolved through a proper accounting of asymmetries in the spectral functions between positive- and negative-energy states.

The alpha particle emission from 90 to 140 MeV ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$${+}^{181}$Ta fusion-evaporation reactions has been studied. The comparisons of the experimental spectral shapes and multiplicities with statistical model predictions indicate a need to use an excitation energy dependent level-density parameter a=A/K in which K increases with excitation energy. This increase is more rapid than that in lower mass nuclei. The effect of this change in level density on the prescission multiplicities in fission is significant.

A new superdeformed band with an intensity ∼5% relative to the yrast superdeformed band has been observed in ${}_{}{}^{194}{}_{}{}^{}\mathrm{Pb}$. Evidence for a second new band corresponding to the signature partner is also presented. These bands were observed with gammasphere early implementation via the ${}_{}{}^{174}{}_{}{}^{}\mathrm{Yb}$${(}^{25}$Mg, 5n) reaction at a beam energy of 130 MeV. The rotational characteristics of the new bands suggest an interpretation involving particle-hole excitations in the doubly-magic ${}_{}{}^{194}{}_{}{}^{}\mathrm{Pb}$ superdeformed core. The results are compared to neighboring nuclei and recent theoretical calculations, and possible configurations are suggested.

Recent Coulomb shift calculations for the level structure of the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ and ${}_{}{}^{20}{}_{}{}^{}\mathrm{F}$ nuclei predict that the $3_3^{+}$ state at 2.966 MeV in ${}_{}{}^{20}{}_{}{}^{}\mathrm{F}$ is the mirror of the 2.646 MeV state in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$, which is of considerable importance for the reaction rate of ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$(p,γ${)}^{20}$Na. Shell model predictions suggest a lifetime of 3.5 fs for the state in ${}_{}{}^{20}{}_{}{}^{}\mathrm{F}$, in disagreement with the experimentally determined value of 60±40 fs. The lifetime of low excited states in ${}_{}{}^{20}{}_{}{}^{}\mathrm{F}$ has therefore been remeasured using the Doppler shift attenuation method (DSAM) and an upper limit of ≤12 fs for the 2.966 MeV state has been obtained.