The experimental results of the dependence of fragment mass yield distribution and related physical observables on the incident energy in intermediate energy nucleus-nucleus collisions reported recently are interpreted with a modified statistical model and relevant averaging techniques. The model reproduces the trends of the variation of mass yield distribution with incident energy quite well. It can also explain the experimental systematics of the incident energy dependence of physical variables with statistical features.

This is an extension of the earlier work of Gardner and Moniz [Phys. Rev. C 36, 2504 (1987)] in the context of the quark-exchange model, in which effective hadron theories were constructed and their resulting physical observables were compared to the exact observables defined by the underlying quark model. The earlier U(1) study of the binding energy and form factor of a ${\mathit{q}}^2$q¯ ${}_{}{}^2{}_{}{}^{}$ system is augmented, and it is extended in two different ways. First, the momentum distribution in U(1) color is now examined as well, since it is an observable which manifests behavior qualitatively distinct from that of an inert meson description; and, second, the hadronic theory construction is generalized to SU(N) color.

Models that are successful in hadronic spectroscopy, viz., the nonrelativistic quark model, bag models, and QCD sum rules, are used to shed light on the Okamoto-Nolen-Schiffer anomaly in nuclear physics.

The analyzing power ${\mathit{A}}_{\mathit{y}}$ was measured for ${\mathrm{\pi }}^{+}$${\mathrm{-}}^{15}$N→ elastic scattering at ${\mathit{T}}_{\mathrm{\pi }}$=164 MeV between 40° and 100° using a polarized ${}_{}{}^{15}{}_{}{}^{}\mathrm{NH}_3^{}{}_{}{}^{}$ target. Within the statistical accuracy of the data ${\mathit{A}}_{\mathit{y}}$(θ) was found to be zero over the full angular range. These data together with differential cross sections from the literature are compared with theoretical predictions based on a momentum-space coupled-channel formalism. While the cross section is very well reproduced there are large discrepancies in the analyzing power for which large spin effects are predicted close to the cross-section minima. Possible deficiencies in the theoretical model are discussed.

We have studied kaon production from the interaction of pions with nucleons in heavy-ion collisions at energies below the threshold for kaon production in the nucleon-nucleon interaction in free space. It is found that this contribution is less than 25% of the total kaon yield. The main contribution to kaon production is from baryon-baryon interactions and its magnitude depends sensitively on the nuclear equation of state at high densities.

This Brief Report presents a reanalysis of the energy scale of published measurements by Johnson et al. and Jury et al. of the ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$(γ,${\mathit{n}}_0$) cross section which brings the two sets into good agreement. This leads directly to new (${\mathit{T}}_{<}$) isospin assignments for levels previously reported by Ajzenberg-Selove at energies of 14.4, 15.2, and 15.6 MeV.

The elastic scattering of 280-MeV ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ off ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been measured. The angular distribution, extending up to 38° in the c.m. system, displays a Fraunhofer crossover followed by a structureless falloff, indicative of the influence of nuclear refraction. Results of an optical-model analysis of the data, using phenomenological and folding model potentials, are presented.

The fission angular distributions for the systems ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$${+}^{232}$Th, ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ have been measured at E∼50 and 53 MeV. The measured fission fragment anisotropy values are in good agreement with the expectations of a standard statistical model.

Calculations are presented of the nuclear tensor term in the proton-nucleus optical model potential, generated by the relativistic impulse approximation. We first show that previously published expressions for this term make an unnecessary approximation, and second, clarify its effects in proton-nucleus elastic scattering at intermediate energies. The effects of the nuclear tensor term alone on the spin observables ${\mathit{A}}_{\mathit{y}}$ and Q for p${+}^{40}$Ca and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ targets, at 650- and 800-MeV incident laboratory energy are shown. We find that the overall effect of the nuclear tensor term is in general quite small, except for the heaviest target considered.

Various forms of the long-wavelength, nonrelativistic nuclear Compton amplitude are discussed. Simple manipulations allow the usual low-energy theorem for the amplitude to be cast into a manifestly gauge-invariant form, which facilitates interpretation.

The low-lying electric dipole distribution for ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ is examined in detail in a large basis nonspurious shell model which includes up to 3ħω of excitation. A very strong enhancement of the E1 strength between 1 and 4 MeV of excitation is predicted when Woods-Saxon single-particle wave functions are used. The relativistic Coulomb excitation cross section is underestimated. However, an analysis of the contributions to the E1 matrix elements indicates that small changes in the structure of the low-lying states can lead to a significant increase in the predicted E1 strengths, so that excitations normally omitted from shell-model calculations are not necessarily needed to explain the anomalous Coulomb cross section.

Microscopic calculations of nuclear reaction cross sections and total reaction probabilities are compared with measurements for the d+Si, ${}_{}{}^{3,4}{}_{}{}^{}\mathrm{He}$+Si, and d+Ge systems at energies ranging from 2 to 53 MeV/nucleon. Good agreement is obtained, except for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$+Si at the very lowest energies, when zero-range nucleon-nucleon forces are assumed and realistic nuclear density distributions are used in the tail regions, where the models are most sensitive. The agreement is less good for finite-range forces. A strong absorption model gives much poorer agreement with the recent ${}_{}{}^4{}_{}{}^{}\mathrm{He}$+Si measurements than do the microscopic models.

We discuss the recent suggestion by Thomas and Holinde that the neutral πNN coupling constant obtained in the Nijmegan phase-shift analysis of pp scattering data differs from the charged πNN coupling constant because of a form-factor effect and therefore is not an indication of charge independence. We place this suggestion in the context of a more global understanding of the πNN form factor, and specify carefully the distinction between the chiral limit and the ${\mathit{q}}^2$=0 limit to clarify the role of the πNN form factor in the Goldberger-Treiman relation.

Single-nucleon removal in relativistic and intermediate energy nucleus-nucleus collisions is studied using a generalization of Weizsäcker-Williams theory that treats each electromagnetic multipole separately. Calculations are presented for electric dipole and quadrupole excitations and incorporate a realistic minimum impact parameter, Coulomb recoil corrections, and the uncertainties in the input photonuclear data. Discrepancies are discussed. The maximum quadrupole effect to be observed in future experiments is estimated and also an analysis of the charge dependence of the electromagnetic cross sections down to energies as low as 100 MeV/nucleon is made.

A method to determine spins, I, associated with transitions in superdeformed rotational bands in the mass 190 region is described and analyzed for conditions of validity. It contributed significantly to two recent articles proposing the relevance of pseudospin to some of these bands. An expansion of dI/dω in even powers of the rotational frequency, ω, is fitted, and its extrapolation down to ω=0 is integrated to obtain I. Typical errors for data with smaller backgrounds are 0.05ħ to 0.1ħ. A related method employing directly an expansion of the spins in odd powers of ω is briefly compared to this method. The dI/dω method has advantages for the crucial task of assessing the fit in the extrapolation region.

Multinucleon transfer reactions between ${}_{}{}^{170}{}_{}{}^{}\mathrm{Er}$ ions and ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{W}$ targets with on-line mass separation were used to produce neutron-rich A=168 isotopes. β and γ spectroscopy was used to study the decay of these activities. A new isomer of holmium, ${}_{}{}^{168}{}_{}{}^{}\mathrm{Ho}_{}^{\mathit{m}}{}_{}{}^{}$, was identified to decay by an isomeric transition with a half-life of 132(4) s. A decay scheme for the most neutron-rich A=168 isotope, 8.8(3)-min ${}_{}{}^{168}{}_{}{}^{}\mathrm{Dy}$, was determined. Also, a new ${\mathit{Q}}_{\mathrm{\beta }}^{\mathrm{-}}$ value of 2.93(3) MeV for the decay of 3.0-min ${}_{}{}^{168}{}_{}{}^{}\mathrm{Ho}_{}^{\mathit{g}}{}_{}{}^{}$ has been obtained.

We have measured the cross sections for high-energy photon production in ${}_{}{}^{12,13}{}_{}{}^{}\mathrm{C}$${+}^{92,100}$Mo reactions at incident beam energies of 9–14 MeV/nucleon. The bombarding energy dependence, angular distribution, and projectile-target mass dependence of the photon yields at high energy, ${\mathit{E}}_{\gamma }$≥30 MeV, have been examined. Our measurements are consistent with production of these photons via nucleon-nucleon bremsstrahlung, the production mechanism dominant in heavy-ion collisions for E/A≥20 MeV/nucleon.

The quadrupole moment of the highly deformed band built upon the ${\mathit{i}}_{13/2}$ neutron intruder orbital in ${}_{}{}^{135}{}_{}{}^{}\mathrm{Sm}$ has been measured, using the Doppler shift attenuation method and Braune stopping powers, to be 7.0±0.7 e b. These data provide strong evidence that this high-j, N=6 intruder orbital is responsible for the highly deformed states seen in this region. The result is compared to total Routhian surface calculations. A possible explanation for the observed anomalous behavior of the ${\mathit{J}}^{\mathrm{}\left(2\right)\mathrm{}}$ moment of inertia in this nucleus is discussed in terms of quenched static proton pair correlations.

Deuterated liquid scintillator detectors (NE230), which give excellent n/γ discrimination and provide a direct measure of the neutron energy spectrum, have been used to search for 2 to 3 MeV neutrons produced in d+d cold fusion. The apparatus consisted of an electrolytic cell using high-efficiency inverted-well geometry. Several samples of annealed Pd wire and a Pd casting (up to 13 g) were studied over a period of several weeks. An upper limit of ≤${10}^{\mathrm{-}3}$ fusion (n/s g) Pd was obtained corresponding to <7×${10}^{\mathrm{-}24}$ fusion (n/s) dd pair in our samples which excludes most of the reported positive results. Several sources of spurious signals, which could closely mimic signals from fusion neutrons, were also observed.