The recently discovered radioactive decay of heavy nuclei by emission of carbon and neon is described by a model containing elements from both the theory of α decay and that of fission. A key ingredient is the inertial mass, which depends on the superfluid pairing gap of the nucleus. The potential energy is estimated from macroscopic considerations. Theory and experiment fit together in a reasonable way to give an overall picture of exotic decay.

Central collisions of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nuclei with the ${}_{}{}^{107}{}_{}{}^{}\mathrm{Ag}$ and ${}_{}{}^{80}{}_{}{}^{}\mathrm{Br}$ nuclei in nuclear emulsion at 14.6, 60, and 200 GeV/nucleon are compared with proton-emulsion data at equivalent energies. The multiplicities of produced charged secondaries are consistent with the predictions of superposition models. At 200 GeV/nucleon the central particle pseudorapidity density is 58±2 for those events with multiplicities exceeding 200 particles.

Giant resonances were observed in (${\pi }^{+}$,${\pi }^{\mathrm{-}}$) double charge exchange (at $T_{\pi }$=292 MeV) on ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{80}{}_{}{}^{}\mathrm{Se}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ at excitation energies of 28.5, 34.6, and 43.6 MeV, respectively. An angular distribution for ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ was measured and observed to have a dipole shape. The variation of excitation energy above the double isobaric analog state is consistent with an $A^{\mathrm{-}1/3}$ dependence, as expected for giant dipole resonances built on the isobaric analog states. The ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ angular distribution agrees well with a coupled-channels impulse-approximation calculation in which sequential single charge exchange through the isobaric analog to the giant dipole resonance is evaluated.

We study the effect of the antisymmetrization at the level of quarks on the behavior under the exchange symmetry of hadronic aggregates. By imposing $\frac{1}{N_c}$ dominance we are led to an antisymmetrization principle at the level of the hadronic clusters. Its application to multibaryon resonances gives rise to selection rules.

Inclusive proton spectra from reactions induced by ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ projectiles have been decomposed by use of a refined multisource analysis. Yields from centrallike collisions have been extracted and compared with Boltzmann-master-equation predictions. The comparison yields the initial number of degrees of freedom, $n_0$. The excitation energy per initial degree of freedom, $\frac{E^{*}}{n_0}$, is found to be essentially independent of the colliding masses, depending only on the per-nucleon energy of the projectile. An empirical relation connecting $\frac{E^{*}}{n_0}$ with the available incident energy is given.

The neutron spectrum from the reaction ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}({}_{}{}^{64}{}_{}{}^{}\mathrm{Ni},1n){}_{}{}^{155}{}_{}{}^{}\mathrm{Er}$ has been measured at an average spin of $52\hslash$ and for excitation energies between 30 and 36 MeV in ${}_{}{}^{155}{}_{}{}^{}\mathrm{Er}$. Channel and spin selection have been obtained from the Darmstadt-Heidelberg Crystal Ball. The level density in ${}_{}{}^{155}{}_{}{}^{}\mathrm{Er}$ is derived within the framework of a Fermi-gas model. A level-density parameter of $a=\frac{A}{(8.8\mathrm{}\pm 1.3)}$ ${\mathrm{MeV}}^{-1\mathrm{}}$ is deduced.

Evaporation residues following the interaction of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ with targets of ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, ${}_{}{}^{160}{}_{}{}^{}\mathrm{Gd}$, and ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$ were measured in the energy range of $E_{\mathrm{lab}}=5.5\mathrm{}-10$ MeV/nucleon. The experimental system allowed the determination of the cross sections of the complete fusion (CF) and the incomplete fusion (ICF) processes with a sensitivity to ICF processes below the percent level. The ICF processes were observed at all bombarding energies studied, down to energies slightly above the Coulomb barrier. The two processes have very different angular distributions, with the ICF peaked at a significantly larger angle than the CF.

The $\mathrm{D}(e, e^{\prime }p)$ coincidence cross section was measured at angles out of the plane, at an excitation energy of approximately 18 MeV and a momentum transfer of 0.33 ${\mathrm{fm}}^{-1\mathrm{}}$. This is the first reported measurement of the longitudinal-transverse and transverse-transverse interference terms of the electrodisintegration cross section of the deuteron. The longitudinal plus transverse cross section is also reported. The results are in good agreement with a theoretical calculation carried out with use of the Paris potential.

The magnetic moment of ${}_{}{}^{190m}{}_{}{}^{}\mathrm{Os}$ ($I^{\pi }={10}^{-}$; $T_{\frac{1}{2}}=9.9\mathrm{}$ min; $E=1705\mathrm{}$ keV; configuration ${\left|n_1\frac{9}{2}\mathrm{}\right[505\left]\mathrm{}{n}_2\frac{11}{2}\mathrm{}\right[615]\mathrm{}〉}_{{10}^{-}}$) has been measured with the new technique of reorientation-nuclearorientation. As the spin contributions of the two neutrons to the magnetic moment cancel almost completely, it is possible to determine the anomalous neutron orbital $g$ factor directly. The result, $-0.12\mathrm{}\le \delta g_l\mathrm{}\left(n\right)\mathrm{}\le -0.07\mathrm{}$ (90% confidence level), tends to be larger than $\delta g_l\mathrm{}\left(n\right)\mathrm{}\simeq -0.05\mathrm{}$ adopted up to now.

Cross sections and $T_{20}$ analyzing powers for $\mathrm{dA}\to \mathrm{pX}$ are presented. A shoulder in the cross section previously reported at higher energies and for carbon is observed for H, C, and Ti at the same $d$-c.m.-frame proton momentum, $q=0.35\mathrm{}$ GeV/c. At $q<\mathrm{}0.2\mathrm{}$ GeV/c both cross-section and $T_{20}$ data depend only weakly upon the target atomic number $A$. Calculations in the plane-wave impulse approximation with several $\mathrm{NN}$ wave functions, and with either a $\Delta \Delta$ or a six-quark component added, are discussed.

Correlations between intermediate-mass fragments (IMF's) and heavy fragments were measured for ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$-induced reactions on ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Ag}$ and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ at $\frac{E}{A}=84\mathrm{}$ MeV. Correlations of two coincident IMF's show a depletion at small relative velocities $v_{\mathrm{rel}}\le 1$ cm/ns, reflecting the proximity of the two IMF's at the point of creation. However, the time scales for IMF emission derived from this correlation are similar to those of binary-IMF-heavy-recoil coincidences which indicates a sequential nature of multifragment emission in these reactions.

The energy, multiplicity, and mass dependences of the exclusive observable "flow" for heavy-ion reactions are studied in a model which includes mean-field but lacks compression effects. The energy and multiplicity dependences of recently published Plastic-Ball data are qualitatively reproduced but the mass-number dependence is not. This as well as the comparison with other models at present favors viscous hydrodynamics with an ideal-gas equation of state and a closely related microscopic reaction mechanism as candidates for yielding a "flow" compatible with the Plastic-Ball analysis.

The elastic scattering of ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$+${}_{}{}^{58,64}{}_{}{}^{}\mathrm{Ni}$ was measured at sulfur beam energies of 82, 88, 91, 93, 98, 102.5, 108, and 150 MeV. Evidence is found for a marked energy dependence of the optical potential at the strong-absorption radii around the Coulomb barrier, in good agreement with parallel information extracted from the fusion cross sections for the same systems.

Cross sections for the two-body channels populated in the ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$+${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ reaction at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=60.8\mathrm{}$ MeV have been measured by use of a coincidence technique which allows correction for secondary light-particle evaporation. The data show reaction yields with full equilibration of energy and mass-asymmetry coordinates. These results suggest an asymmetric fission mechanism and are contrary to what is expected from the previously proposed "orbiting" mechanism in light systems.

The giant dipole resonance in ${}_{}{}^{224}{}_{}{}^{}\mathrm{Th}$ excited to 44, 64, and 82 MeV was observed following the fusion of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The total $\gamma$ spectrum is analyzed in terms of prefission and postfission $\gamma$ decay. The data can only be fitted by our requiring an enhancement of the giant-dipole-resonance $\gamma$ rays from the prefission nuclei which is explained by a large fission hindrance in the early decay steps from the compound system. A measurement of the $\gamma$-fission angular correlation supports this conclusion and establishes a deformed shape of the compound nucleus.

The flow of light nuclei ($Z=1, 2$) and intermediate-mass nuclear fragments ($3\le Z<\mathrm{}10\mathrm{}$) is measured in collisions of 200-MeV/nucleon Au+Au over a large solid angle. An increase in the fragment-position and momentum-space alignment relative to the reaction plane is observed: The fragments exhibit stronger flow effects than light particles.

Changes in the nuclear density arising from shape fluctuations are calculated in the case of the closed-shell nucleus ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. The main contributions come from self-energy processes which renormalize the single-particle potential. Those due to ground-state correlations are much smaller. Processes involving the coupling to isoscalar vibrations are the most important, the role of isovector modes being small. Changes in the radius and in the diffusivity, of the order of 5% and 20%, respectively, are found.

Uranium-uranium collisions at the energy of the Brookhaven Relativistic Heavy-Ion Collider (100 + 100 GeV per nucleon) are predicted to produce an average of nearly 100 jets with $p_T>3\mathrm{}$ GeV. These jets will on average carry of 70 GeV of transverse energy $E_T$ per unit rapidity. Central collisions produce more transverse energy than this; the $E_T$ distribution extends up to about $\frac{\left(5\mathrm{}{A}^{\frac{4}{3}} {\mathrm{GeV}}^4\right)}{p_{Tmin}^3}$ per unit rapidity, which is 4 times the average. It is estimated that the minijets are likely to undergo further collisions and become thermalized.

First results from measurements of all the shower particles produced in 191 nearly central interactions of a 200-GeV/nucleon ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ beam with nuclear emulsion are presented. The lower limit of the average energy density for the events with multiplicity $n_s\ge 200$ is $〈\epsilon 〉\simeq 1$ GeV/${\mathrm{fm}}^3$.

Out of 30 000 interactions of 3.2-TeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nuclei in Pb, we found that no fast fragments had a charge $Z>\mathrm{}8\mathrm{}$, none with $Z\gtrsim 5.5$ had a charge that differed from an integer by as much as $\frac{1}{3}$, and none with $Z\gtrsim 5.5$ had an angle to the beam > 0.8 mrad. The cross section for production of a fast fragment with $Z>\mathrm{}8\mathrm{}$ or a stable particle with charge $\frac{19}{3}e$, $\frac{20}{3}e$, $\frac{22}{3}e$, or $\frac{23}{3}e$ is less than 240 μb at 90% confidence level. Using a measurement technique with a position resolution of 30 μrad, we found the transverse-momentum distributions for C, N, and O to be Gaussians with widths ≃ 100 MeV/c, similar to those measured in projectile fragmentation of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at a factor 100 lower energy.