Experimental intermediate-mass-fragment multiplicity distributions for the $\frac{E}{A}=80\mathrm{} \mathrm{and} 110$ MeV ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ + ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ reactions are shown to be binomial at all excitation energies. From these distributions, a single binary event probability $p$ can be extracted that has a thermal dependence. Thus, it is inferred that multifragmentation is reducible to a combination of nearly independent emission processes. If sequential decay is assumed, the increase of $p$ with excitation energy implies a contraction of the time scale that is qualitatively consistent with recent fragment-fragment correlation data.

In ${}^{197}$Au-emulsion interactions at $10.6A\mathrm{GeV}$ from the Alternating Gradient Synchrotron at Brookhaven National Laboratory, the projectile fragments (PFs) of charge $Z\ge 2$ exhibit collective flow which is observed in all interactions with different impact parameters. Collective flow increases with the charge of the PFs. But in the case of ${}^{28}$Si-emulsion interactions at $14.5A\mathrm{GeV}$, the PFs of ${}^{28}$Si do not show collective flow.

Fission fragment angular distributions and cross sections have been measured for the reaction of ${}_{}{}^{16}{}_{}{}^{}O+{}_{}{}^{238}{}_{}{}^{}U$ at energies around the Coulomb barrier. Full momentum transfer events were selected using the folding angle technique. The fission fragment anisotropies rise rapidly as the beam energy decreases through the barrier region. This is interpreted as showing that collisions with the tips of the deformed target nucleus lead to quasifission, collisions with the sides to fusion-fission.

Massive, projectilelike fragments (PLF) from the ${}^{209}\mathrm{Bi}{+}^{136}\mathrm{Xe}$ reaction at $E_{\mathrm{lab}}/A=28\mathrm{}\mathrm{MeV}$ were measured in coincidence with lighter charged products and neutrons, detected with $4\pi$ angular coverage. Strong correlations are observed between the deflection angle of the massive fragment, on the one hand, and various experimental measures of energy dissipation, on the other hand. These correlations, as well as the observed broadening of the primary PLF atomic-number distribution with increasing energy dissipation, are strikingly reminiscent of damped reaction features that are well understood in terms of dissipative orbiting.

The NA35 experiment has collected a high statistics set of momentum analyzed negative hadrons near and forward of midrapidity for central collisions of $200A\mathrm{GeV}/c$ ${}_{}{}^{32}{}_{}{}^{}S+\mathrm{S}$, Cu, Ag, and Au. Using momentum space correlations to study the size of the source of particle production, the transverse source radii are found to decrease by $\sim$40% at midrapidity and $\sim$20% at forward rapidity while the longitudinal radius $R_L$ is found to decrease by $\sim$50% as $p_T$ increases over the interval $50<\mathrm{}{p}_T<600\mathrm{MeV}/c$. Calculations using a microscopic phase space approach (relativistic quantum molecular dynamics) reproduce the observed trends of the data.

A comment on the Letter by K. Geiger.

A reply to the comment by M. Asakawa.

The rate of phase-space exploration in the decay of isovector and isoscalar giant quadrupole resonances in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ is analyzed. The study is based on the time dependence of the survival probability and of the spectrum of generalized entropies evaluated in the space of one-particle-one-hole (1p-1h) and 2p-2h states. Three different cases for the level distribution of 2p-2h background states, corresponding to (a) high degeneracy, (b) classically regular motion, and (c) classically chaotic motion, are studied. In the latter case the isovector excitation evolves almost statistically while the isoscalar excitation remains largely localized, even though it penetrates the whole available phase space.

The three-body decay ${}_{}{}^{12}{}_{}{}^{}\mathrm{O}\to 2p+{}_{}{}^{10}{}_{}{}^{}\mathrm{C}$ was studied following production via single-neutron stripping from a radioactive ${}_{}{}^{13}{}_{}{}^{}\mathrm{O}$ projectile. This is the first observation of two-proton emission from an unbound ground state where the one-proton emission channel is energetically closed beyond the lightest case of ${}_{}{}^6{}_{}{}^{}\mathrm{Be}$. No evidence for ${}_{}{}^2{}_{}{}^{}\mathrm{He}$ emission is seen, despite predictions for a large diproton branching ratio. An upper limit of 7% (95% C.L.) is established for this decay branch. The implications of the small diproton branching ratio observed here and seen previously in ${}_{}{}^6{}_{}{}^{}\mathrm{Be}$ are discussed.

Fusion-evaporation cross sections for ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ + ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$ have been measured with high accuracy in the energy range around the Coulomb barrier. The data yield an "experimental distribution of fusion barriers" around 13 MeV wide, which displays structure characteristic of strong phonon couplings with two large well "resolved" peaks, and a smaller peak at lower energies, which is essential for fitting the low-energy cross section. This is obtained only when the target and projectile double-phonon excitations are taken into account. This is the first time that such complex surface vibrations have been identified in a fusion experiment.

The ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ni}$ nucleus has been identified among the products of deep-inelastic reactions of ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ projectiles bombarding ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ targets. Three new states, including the high-lying $2^{+}$ (2033 keV) and the 0.86 ms $5^{-}$ isomer, indicate a substantial subshell closure at neutron number $N=40\mathrm{}$. The level structure and the observed very slow $E3\mathrm{}$ transition speed are discussed within the shell model.

In a high-resolution electron scattering experiment ten $3^{+}$ states in ${}^{26}$Mg have been identified, increasing the world data on $M3\mathrm{}$ transitions severalfold. Differential cross sections have been measured and magnetization current densities and form factors have been deduced. It is found that while the level of agreement of the $B\left(M3\mathrm{}\right)$ values with shell-model predictions varies from state to state, the summed $B\left(M3\mathrm{}\right)$ strengths are in good agreement. No overall quenching of the $M3\mathrm{}$ strength is found, and it is concluded that no renormalization of the free nucleon g factors is needed.

Measurements were performed for the photodisintegration cross section of the deuteron for photon energies from 1.6 to 2.8 GeV and center-of-mass angles from 37° to 90°. The measured energy dependence of the cross section at ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=90\mathrm{}°$ is in agreement with the constituent counting rules.

We obtain the perturbative QCD (PQCD) prediction for the leading twist deuteron form factor, treated as a pair of nucleons in nonrelativistic bound state. It is <${10}^{-3\mathrm{}}$ times experiment at $Q^2=4\mathrm{}$ Ge${\mathrm{V}}^2$, suggesting that PQCD is not relevant to the deuteron form factor at present values of $Q^2$, or that nonnucleon (e.g., "hidden color") degrees of freedom must be included for a correct description of the deuteron. The tree-level amplitude $\sim e{g}^{10}$ and is the sum of several ${10}^6$ Feynman diagrams, making it an interesting case study in the behavior of perturbation theory.

The transverse-longitudinal asymmetry $A_{T{L}^{\prime }}$ in ${}_{}{}^3{}_{}{}^{}\overrightarrow{\mathrm{He}}(\overrightarrow{e}, e^{\prime })$ quasielastic scattering at momentum transfer $Q^2=0.14\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ has been measured to be 1.52 ± 0.55(stat) ± 0.15(syst)%. The plane wave impulse approximation (PWIA) prediction for this measurement ranges from 2.1% to 2.9%, where the variation is due to uncertainty in the initial state wave function, nucleon form factors, and off-shell prescription. The data may suggest a suppression with respect to the PWIA, which has also been observed for the unpolarized longitudinal response function.

Electron capture from an unfilled atomic $s$ orbital is investigated theoretically. Analyses are carried out for two simple situations, a mirror transition of a nucleus with a nucleon in an outer $s_{\frac{1}{2}}$ state and a Gamow-Teller transition decreasing the nuclear spin by one unit. It is shown that the hyperfine interaction between electron and nuclear spins has a great influence on the rate of electron capture at temperatures small compared to the hyperfine splitting. The possibility of inducing electron capture with resonant electromagnetic fields is discussed.

We report measurements of spin correlations and analyzing powers in ${}_{}{}^3{}_{}{}^{}\overrightarrow{\mathrm{He}}(\overrightarrow{p}, 2p)$ and ${}_{}{}^3{}_{}{}^{}\overrightarrow{\mathrm{He}}(\overrightarrow{p}, pn)$ quasielastic scattering as a function of momentum transfer and missing momentum at 197 MeV using a polarized internal target at the Indiana University Cyclotron Facility Cooler Ring. At sufficiently high momentum transfer we find ${}_{}{}^3{}_{}{}^{}\overrightarrow{\mathrm{He}}(\overrightarrow{p}, pn)$ spin observables are in good agreement with free $p-n$ scattering observables, and therefore that ${}_{}{}^3{}_{}{}^{}\overrightarrow{\mathrm{He}}$ can serve as a good polarized neutron target. The extracted polarizations of nucleons in ${}_{}{}^3{}_{}{}^{}\overrightarrow{\mathrm{He}}$ at low missing momentum are consistent with Faddeev calculations.

A spectroscopic study of the ${}_{\Lambda }{}^{12}{}_{}{}^{}\mathrm{C}$ hypernucleus by the (${\pi }^{+}, K^{+}$) reaction has been performed using a new superconducting kaon spectrometer (INS-SKS) at the KEK 12 GeV Proton Synchrotron with an energy resolution of 2 MeV (FWHM). In addition to two prominent peaks which correspond to the $s$ and $p$ orbitals of a $\Lambda$ hyperon, for the first time two smaller peaks were clearly observed at excitation energies of 2.6 and 6.9 MeV. These two peaks are interpreted as states where the ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ excited core and a $\Lambda$ hyperon in the $s$ orbit are weakly coupled. The excitation energies and the cross sections of these peaks provide information on the $\Lambda N$ interaction.

Scalar and vector interactions, with the scalar interaction coupled to a composite spin-½ system so as to cause a shift of its mass, are shown to obey a low-energy theorem which guarantees that the second order interaction due to $Z$ graphs is the same as for a point Dirac particle. Off-shell and contact interactions appropriate to the composite system cancel, and this is verified in a model of a composite fermion. The result suggests a justification for the use of the Dirac equation as it has been used in relativistic nuclear scattering and mean field theories.

The current theoretical analyses of the parity nonconserving (PNC) experiments in light nuclei fail to provide a consistent description of the experimental data for ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$, ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$, and ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$. We perform a "piecewise" analysis of the PNC matrix elements in the $0p_{\frac{1}{2}}-0\mathrm{}{d}_{\frac{5}{2}}-1\mathrm{}{s}_{\frac{1}{2}}$ model space and show that by using a proper overall normalization of the isoscalar and isovector parts we can consistently describe all three PNC experimental data. New calculations are also presented for the $s-p-sd-pf$ model space which support our analysis.