The ${}_{}{}^6{}_{}{}^{}\to \mathit{p}+(\mathit{n}\mathit{\alpha }$) spectral function for the proton-knockout reaction ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(e,e’p) has been measured in parallel kinematics in the missing-momentum range -100<$p_m$<200 MeV/c. The data below α breakup are well described by a three-body (αnp) model of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$. The shell model with discrete energy eigenstates cannot describe the data. The experimental spectroscopic strength below α breakup amounts to 0.79(10), compared to 0.87 as predicted by the three-body model and 1.33 as calculated from a schematic harmonic-oscillator shell model. The discrepancy between the predictions of the two models is discussed.

Recently, two scientific papers have reported positive detection of nuclear radiation from similar electrochemical cells operating with deuterated water. We have experimented with similar electrolytic cells and have looked for energetic charged particles which are characteristic of nuclear fusion reactions. We report on six variations of the cell, with an upper limit of 0.005 detected particles/${\mathrm{cm}}^3$ sec. Within background statistics, we observe no nuclear fusions.

Pseudorapidity distributions of relativistic singly charged particles in oxygen-induced emulsion interactions at 14.6, 60, and 200 GeV/nucleon are studied. Limiting fragmentation behavior is observed in both the target and projectile fragmentation regions for a central as well as for a minimum-bias sample. Comparisons with the fritiof model reveal that the picture of fragmenting strings successfully describes the observed data.

The structure in the β-delayed proton spectra of the precursors ${}_{{}_{66}{}^{147}{}_{}{}^{}}{}^{}{}_{}{}^{}\mathrm{Dy}_{}^{\mathrm{g}}{}_{}{}^{}$, ${}_{{}_{68}{}^{149}{}_{}{}^{}}{}^{}{}_{}{}^{}\mathrm{Er}_{}^{\mathrm{g}}{}_{}{}^{}$, and ${}_{{}_{70}{}^{151}{}_{}{}^{}}{}^{}{}_{}{}^{}\mathrm{Yb}_{}^{\mathrm{g}}{}_{}{}^{}$ is analyzed within the framework of a doorway-state model. Indications from γ-ray decay studies, β strength-function measurements, and calculations of state densities and Gamow-Teller strength distributions, lead us to suggest that some of the observed proton transitions arise from the preequilibrium decay of doorway states populated in ${\beta }^{+}$ decay or electron capture.

We report on the measurements of electron pair production in p-Be collisions at 1.0, 2.1, and 4.9 GeV beam kinetic energies. The invariant-mass and transverse-momentum spectra are presented, along with the total cross sections. A rapid decrease in the integrated cross section is observed as the beam energy is reduced. Comparison of the excitation function for dielectron ($e^{+}$$e^{\mathrm{-}}$) and dipion (${\pi }^{+}$${\pi }^{\mathrm{-}}$) production suggests that the dominant production mechanism at beam kinetic energies 2.1 and 4.9 GeV may be ${\pi }^{+}$${\pi }^{\mathrm{-}}$ annihilation.

The observed saturation of temperature and of linear momentum transfer per incident nucleon in intermediate-energy nuclear reactions is studied in the model of promptly emitted particles. We demonstrate that only with the inclusion of two-body collisions is very good agreement with experimental data obtained.

Exclusive differential cross sections for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(γ,n${)}^{15}$O process have been measured for $E_{\gamma }$=150, 200, and 250 MeV and ${\theta }_L$=49°, 59°, and 88°. This measurement is the first of its type to be reported for the energy region above the pion production threshold. An uncollimated bremsstrahlung beam was incident on an ${\mathrm{H}}_2$O target, and neutrons were measured with a recoil proton spectrometer with resolution sufficient to identify the residual ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$ ground state. The results are compared to (γ,p) data and to calculations including effects from meson exchange currents.

In an axially symmetric, strongly rotating quadrupole deformed nucleus, the projection K of the angular momentum along the symmetry axis is a partially conserved quantity. A K isomer (K=25) at low excitation energy has been observed in ${}_{}{}^{182}{}_{}{}^{}\mathrm{Os}$ which decays into the ground-state band (K=0). The associated electromagnetic lifetime at spin I≊25 can be interpreted in terms of tunneling of a system displaying strong pairing fluctuations across a barrier which separates configurations in which the nucleus rotates about the symmetry axis and about an axis perpendicular to it. A hindrance factor ≊${10}^{\mathrm{-}6}$–${10}^{\mathrm{-}9}$ for the process is calculated, in overall agreement with the data.

Secondary minima in the potential-energy surfaces of even-even nuclei are searched for through nonaxial Hartree-Fock-Bogoliubov calculations based on a finite-range, density-dependent effective force. This study covering the mass region 64<A<208 is intended to select nonfissile nuclei which would develop shape isomers. Results are presented for nuclei which seem to be the most interesting candidates for experimental investigations.

It is pointed out that pions from weak decay of Λ hypernuclei could be due to production of the H dibaryon, whose mass could be as light as that of two nucleons. Possibility of such a light H particle has been shown recently by lattice QCD calculations. The mesonic-decay rate of Λ hypernuclei to produce the H is calculated to demonstrate experimental feasibility of a search for the H by detecting such pions. The ${\pi }^{+}$ decay, in particular, is shown to be a unique signature of the H production.

We introduce a new string model (venus 2) for ultrarelativistic heavy-ion collisions, based on color exchange between quarks and also between antiquarks. These two mechanisms affect the rapidity distribution of baryons differently: Quark color exchange shifts baryons towards central rapidity, antiquark color exchange moves baryons back towards large (c.m.) rapidities. We obtain almost flat baryon rapidity distributions for symmetric A+A collisions. Rapidity distributions for proton-nucleus collisions show a forward plateau rather than a forward peak, in agreement with data.

We find that narrow lines at 1043 and 1062 keV in the summed-energy, 180°-correlated two-photon spectrum from ≊6-MeV/nucleon U+Th collisions can be produced by cascades from high-spin states (${32}^{+}$) in ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. We see no evidence for narrow two-photon lines in U+Th, Th+Th, and U+U collisions corresponding to the electron-positron lines seen by others: In the summed-energy region between 1.2 and 2.0 MeV, we set an upper limit for the cross section of 6×${10}^{\mathrm{-}31}$ ${\mathrm{cm}}^2$ averaged over a target thickness of 1 mg/${\mathrm{cm}}^2$.

The binding energy, density, and incompressibility (saturation properties) of normal nuclear matter are reproduced using a Lagrangian with approximate chiral symmetry. The pion-ring series including nucleons and Δ’s provides the necessary attraction and its density dependence, while the effects of the scalar field are not significant, and vacuum-polarization effects are expected to be small.

Angular distributions of the analyzing powers ${}_{}{}^{\mathrm{T}}{}_{}{}^{}\mathrm{T}_{\mathrm{k}0}^{}{}_{}{}^{}$ (k=1,2,3), $T_{20}$, and $T_{21}$ for elastic and quasielastic scattering of 110-MeV polarized ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ from ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and the cross section for quasielastic scattering have been measured. Vanishing odd-rank tensor analyzing powers and the validity of the shape-effect relations indicate the importance of the projectile deformation for the interaction potential. The data are well explained by coupled-channel calculations using realistic double-folding potentials and taking into account projectile deformation and excitation.

It is shown that a schematic three-body force in addition to a general two-body force leads to a strongly improved description of the energies of A=4–16 nuclei. The values of the two strength parameters of the proposed three-body force, which are obtained empirically from energies and static moments of p-shell nuclei, are found to be similar to those of a realistic three-nucleon force.

Calculations have been made to explore the effect of configuration mixing in a large basis on the fragmentation of the ‘‘stretched’’ M6 strength in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. Our work extends a previous calculation, which allowed a single particle in the $f_{7/2}$ orbit and the remainder in the (unrestricted) 1$d_{5/2}$ and 2$s_{1/2}$ orbits, by also allowing up to four particles in the 1$d_{3/2}$ orbit. It is found that configuration mixing within this expanded basis gives an improved description of the spectrum and several other properties of the observed states.

The γ-ray spectrum in the giant dipole resonance (GDR) region associated with the reaction ${}_{}{}^{40}{}_{}{}^{}$Ar${+}^{70}$Ge at 10 MeV/nucleon has been measured in coincidence with residues of the heavy composite systems whose excitation energy was $E^{\mathrm{*}}$=230 MeV. From the statistical-model analysis, it is deduced that the GDR strength is consistent with 100% of the energy-weighted sum rule, the energy is 16±1 MeV while the width is ${13}_{\mathrm{-}2}^{+1\mathrm{}}$ MeV. This value is not very different from the one measured at $E^{\mathrm{*}}$=130 MeV, thus pointing to saturation effects in the damping of the GDR.

The special degeneracy which occurs in the harmonic-oscillator potential when two of the frequencies have ratios of small integer numbers is exploited. Favored shell energies occur for particle numbers which vary with the third frequency. Applications to realistic nuclear potentials show that this degeneracy leads to special shell effects for axial shapes (1:1 ratio) but also for the 2:1 ratio exemplified by the triaxial ground state of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ and triaxial superdeformed high-spin isomers in the light Hf nuclei.

We report on the first observation of subthreshold antiproton production in nucleus-nucleus collisions. This measurement was made for the system ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ at a bombarding energy of 2.1 GeV/nucleon (kinetic energy per NN pair in the c.m. frame ∼850 MeV). A differential cross section $d^2$σ/dP d Ω of 80±40 nb/sr (GeV/c) was measured for p¯ production at 1.9 GeV/c and 0°. This result is 3 orders of magnitude larger than that predicted by a calculation incorporating internal motion of the nucleons in the colliding nuclei.

When observed in singles, complex fragments associated with the 18A-MeV ${}_{}{}^{139}{}_{}{}^{}\mathrm{Ni}$ reaction present a complex invariant-cross-section pattern without an obvious source, while the center-of-mass velocities of the coincident binary events span the entire range from complete fusion to near projectile velocities. By gating on a given value of the source velocity, it is possible to characterize precisely the product formed in the corresponding incomplete-fusion process and its decay.