Total reaction cross sections for inclusive pion double charge exchange have been obtained at incident pion energies of 180 and 240 MeV for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^{6.7}{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{103}{}_{}{}^{}\mathrm{Rh}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. An explanation of the dependence of these cross sections upon the mass and charge of the target nucleus and the charge of the incident pion is suggested in terms of a phenomenological model in which successive single-charge-exchange processes compete with more probable processes such as quasifree scattering.

Quasielastic-scattering cross sections of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$${+}^{58}$,64Ni have been measured in the energy range $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=50.0–76.5 MeV. The transfer channels with a large cross section produce a considerable effect on the elastic scattering for ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$${+}^{64}$Ni, while the effect is small for ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$${+}^{58}$Ni because of the small transfer yield. A coupled-channels calculation including one neutron transfer and inelastic excitation explains well not only the energy dependence but also the isotope dependence of the quasielastic scattering with a single energy- and isotope-independent bare potential.

The dilepton yield at invariant masses between 2$m_{\pi }$ and 1 GeV is shown to be reduced substantially if a baryon-rich quark-gluon plasma is formed in high-energy heavy-ion collisions. We suggest therefore to measure the total dilepton yield in this region of invariant masses as a function of the incident energy. The onset of a baryon-rich quark-gluon plasma is then signaled by a decrease in this excitation function.

To investigate the effect of vacuum polarization in the Coulomb interaction between hadrons, the relative differential cross section for elastic ${}_{}{}^{12}{}_{}{}^{}\mathrm{-}_{}^{12}{}_{}{}^{}$C scattering at ${\mathrm{E}}_{\mathrm{lab}=4\mathrm{}}$ MeV has been measured with high precision. The data are compared to theoretical calculations that take into account the contribution of the Ühling potential and other small contributions. Data and calculation agree within 1.5 standard deviations. This constitutes a test of the vacuum polarization on the 7% level.

The reaction mechanism of heavy-ion charge-exchange scattering at low and intermediate incident energies is studied theoretically. Contributions of direct charge exchange due to central and tensor isovector interactions and of charge exchange via sequential proton and neutron transfer are taken into account in one-step and two-step exact-finite-range distorted-wave Born-approximation calculations. The nuclear structure of the intermediate and final states is described within the shell model. Calculations for ${}_{}{}^{12}{}_{}{}^{}$C${(}^{12}$C, ${}_{}{}^{12}{}_{}{}^{}$N${)}^{12}$B2 indicate that direct charge exchange is safely dominant for incident energies E/A≳100 MeV.

Nuclear transport models including density- and momentum-dependent mean-field effects are compared to intranuclear-cascade models and tested on recent data on inclusive p-like cross sections for 800A-MeV La+La. We find a remarkable agreement between most model calculations but a systematic disagreement with the measured yield at 20°, possibly indicating a need for modification of nuclear transport properties at high densities.

Inclusive electron-scattering measurements of Δ electroexcitation in nuclei are reported. Electrons with energies of 0.96, 1.1, 1.3, and 1.5 GeV were scattered from ${}_{}{}^1{}_{}{}^{}\mathrm{H}$, ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, C Fe, and W at 37.5°, corresponding to $Q^2$=0.20–0.52 (GeV/c${)}^2$ at the Δ peak. The centroid of the Δ-region cross-section peak is above that for the free nucleon and it shifts to higher invariant mass as $Q^2$ increases. The A dependence in the dip region and ratios of nuclear to nucleon integrated cross sections indicate that at these $Q^2$ values there is little specifically nuclear, e.g., quasideuteron, background contribution.

We consider interference effects in the inclusive emission of two identical particles from a compound nucleus. Statistical assumptions result in a correlation of the emitted particles that depends upon the coherence properties of the level widths in a form similar to that describing fluctuations in an exclusive cross section. A schematic application to the decay of a rapidly rotating compound nucleus shows that the observed source size can depend upon the kinematics of the measurement.

Triple differential cross sections of charged pions were measured for collisions of Ne projectiles at E/A=800 MeV with NaF, Nb, and Pb targets. The reaction plane was estimated event by event from the light-baryon momentum distribution. For heavy targets, preferential emission of charged pions away from the interaction zone towards the projectile side was observed in the transverse direction. Such a preferential emission, which is not predicted by cascade calculations, may be attributed to a stronger pion absorption by the heavier spectator remnant.

Cross sections for the fusion of ${}_{}{}^{10}{}_{}{}^{}$,11B${+}^{10}$,11B have been measured in the energy range from 1.5 to 5 MeV/nucleon. The ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ system unexpectedly presents a hindered fusion cross section when compared to the ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ reactions and to standard model predictions. The missing fusion cross section was diverted to the ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ exit channel with a total kinetic energy characteristic of strongly damped collisions. Q values and kinematical analysis together with angular distributions suggest a binary symmetric decay of the composite ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ system.

We describe a method for determining the four-momentum distribution of nucleons in nuclei which is particularly sensitive to large momenta. It may also prove useful in probing the differences between bound and free nucleons.

The time scale of fission at initial nuclear temperatures of about 5 MeV is deduced from the number of neutrons evaporated prior to and after scission in the reactions ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$ and ${}_{}{}^{154}{}_{}{}^{}+(838\mathrm{}$ MeV) ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$. The prescission lifetime for fission with symmetric mass splits is longer than for asymmetric mass splits. For symmetric mass splits the excitation energy at scission is only about 60 MeV and independent of the initial excitation energy which is consistent with a prescission lifetime in the order of ${10}^{\mathrm{-}20}$ s.

Partial-wave cross sections for fusion of ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zr}$ at energies of 5% and 7% above the Bass-model fusion barrier have been measured with the Darmstadt-Heidelberg Crystal Ball. The distribution for fusion with the more neutron-deficient target ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$ exhausts the unitarity limit for lower angular momenta. In contrast, fusion with the slightly more neutron-rich target ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}$ yields a broad angular momentum distribution with cross sections well below unitarity even for small partial waves.

We discuss the behavior of the neutron charge form factor in a nuclear environment using the framework of a chiral πρω Lagrangian. For momentum transfers of 0.4 (GeV/c${)}^2$ and larger, the medium renormalization of fundamental meson parameters leads to a sizable decrease in the neutron charge form factor. This effect might be seen in an upcoming high-precision experiment to determine the electric form factor of the neutron through scattering of polarized electrons from polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. We also find that the effective nucleon mass and axial-vector coupling constant $g_A$ are quenched.

Correlations between projectilelike and targetlike fragments have been measured in the reaction ${}_{}{}^{27}{}_{}{}^{}\mathrm{MeV}$/nucleon ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$. These correlations can be consistently interpreted in the framework of an abrasion model including dissipation. However, they can also be described by a binary process in which, before decaying sequentially by particle emission, projectile and target share an approximately equal amount of excitation energy with no significant mass transfer.

Relative populations of particle-unbound states were measured for ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ nuclei emitted behind the grazing angle for the ${}_{}{}^{14}{}_{}{}^{}$N${+}^{\mathrm{nat}}$Ag reaction at E/A=35 MeV. The populations of states decaying by proton and α-particle emission are inconsistent with purely statistical distributions, indicating that the intrinsic degrees of freedom of the fragmenting system may not be fully equilibrated at the instant the fragment separates from the rest of the system.

Measurements of conversion rates are reported for the first time in one- and two-electron systems, for the 14.4-keV nuclear state in ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$. The total half-life of this state deduced for the two-electron ion is 100±5 ns, and that deduced for the total spin F=1 state of the one-electron ion is 79±6 ns.

Using the 1/N expansion technique, the nature of the crossband transitions in collective models is studied. As an example, the γ→g E2 transition is calculated to next-to-leading order. The closed expressions derived are general and will be useful in the analysis of experimental data in terms of both the sd and sdg boson models. The formalism establishes a direct contact with the geometrical model, illuminating the nature of the γ→g transitions and clarifying some earlier results obtained using an SU(3) basis.

Corrections to the Fermi matrix element for superallowed transitions due to isospin nonconservation are reexamined. The sources of theoretical uncertainty and the possibility of a previously neglected correction based on the mismatch between the spectator nucleons are investigated. The consequences to the conserved-vector-current hypothesis and the Kobayashi-Maskawa mixing angles are discussed.

The first $\mathrm{Pb}(n, n^{\prime }x)$ data (at 65 MeV) are compared to earlier (61-66 MeV) ($p, p^{\prime }x$) data. The isovector sensitivity of these nucleon probes is used to determine $\frac{M_n}{M_p}\simeq \frac{N}{Z}=1.54\mathrm{}$ for the giant quadrupole resonance (GQR). This result is consistent with other direct GQR measurements, $2_1^{+}$ data connected through core polarization, and several microscopic random-phase-approximation calculations, but in disagreement with a $\frac{{\pi }^{-}}{{\pi }^{+}}$ study which gives $\frac{M_n}{M_p}=3.8\mathrm{}\pm 1.2$.