Two theoretical approaches to y scaling based on different treatments of final state interactions are compared. Experimental data show scaling in both treatments; however, there is strong disagreement between data and the West prediction based on a Faddeev momentum distribution. Partial inclusion of final state interaction by Sick, Day, and McCarthy substantially improves the comparison with data. Dramatic sensitivity to the treatment of final state interaction suggests that existing theoretical analyses are not decisive.

The level structures of odd proton ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$ and ${}_{}{}^{141}{}_{}{}^{}\mathrm{La}$ have been studied in γ-ray singles, Compton-suppressed singles, coincidence, and angular correlation experiments. No evidence was observed to support the existence of any levels in ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$ in the gap between the 166-keV $d_{5/2}$ level and the 1209-keV ${\mathrm{}(1/2)\mathrm{}}^{+}$ level, even though data were accumulated long enough to observe indirect feeding of the ${\mathrm{}(1/2)\mathrm{}}^{+}$ level. Additional spin and parity assignments are suggested for a number of levels in ${}_{}{}^{141}{}_{}{}^{}\mathrm{La}$ based on angular correlation measurements.

A systematic study of the radioactive background in materials used in Ge-detector fabrication was conducted prior to the construction of an ultralow-background, 135 ${\mathrm{cm}}^3$ prototype detector. The background from primordial radioactivities in the new system was lower by factors of between 1.5×${10}^3$ and 2.5×${10}^4$ when compared to commercial low-background detectors. Data were collected for 8089 h with the detector located 1438 m underground, resulting in improved lower limits for the half-lives for both two-neutrino and neutrinoless ββ decay of ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ to the ground state of ${}_{}{}^{76}{}_{}{}^{}\mathrm{Se}$ and for the neutrinoless ββ decay to the first excited state of ${}_{}{}^{76}{}_{}{}^{}\mathrm{Se}$. The results of four recent theoretical calculations are compared in detail and used to extract limits on 〈$m_{\nu }$〉, the Majorana mass of ${\nu }_e$, and on the amplitudes of the couplings of right-handed Majorana neutrinos. The best combination of the lowest background data from recent experiments results in a new limit $T_{1/2}^{0\nu }$≳3×${10}^{23}$ yr, corresponding to 〈$m_{\nu }$〉<2.4 eV neglecting right-handed couplings or 2.8 eV including both right-handed neutrino couplings.

A new method of computing the ground state energy of a Fermi fluid is developed and applied to the hard-sphere Fermi fluids of two and four components. We find the results to be highly accurate for low densities. In this paper we compute and report the perturbation series for the ground state energy for the soft, repulsive, square-well problem at a number of densities for a four-component Fermi system as well as the ladder approximation energies for a hard-sphere potential at the same densities.

Several sets of authors have recently developed a systematic method of obtaining boson realizations of the Lie algebras of the symplectic groups, utilizing the subgroup chain Sp(2Λ)⊃U(Λ). Physical motivation stems both from the Sp(6,R) collective model (noncompact algebra) and various shell-model applications (compact algebra). We present here a number of the simplest examples of interest for shell-model application. These include the LS coupled (identical nucleon) shell-model algebra [for application to the pseudo-SU(3) model] and the Sp(6) model of Ginocchio.

The interacting boson model for giant dipole resonances in deformed nuclei is analyzed by semiclassical means. A geometrical form of the dipole interactions is derived. Deformed dipole states are introduced in the interacting boson model formulation. They are related to dipole states in the dynamic collective model. This makes it possible to show that all the matrix elements of the dipole interaction between the lowest-energy states in the boson and the geometrical model agree to leading order in N. It is concluded that no structural differences exist between the two models for the low-lying states and for large N.

A general method is presented for the construction of intrinsic states in the rotational [SU(3)] limit of the interacting boson model. Explicit results are given for the low-lying bands [leading irreducible SU(3) representations] for three versions of the interacting boson model: the original sd model (IBA-1), the extended version which includes the g boson, and the neutron-proton (IBA-2) model. As an application, U(6)⊃SU(3) and U(15)⊃SU(3) isoscalar factors are derived.

Previous calculations of the electric and magnetic form factors of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ have included various theoretical ingredients (nucleon form factors, mesonic exchange currents, pion-nucleon vertices, etc., . . .). The bearing of these ingredients upon the nuclear current conservation equation is investigated.

On the basis of measured yields for 72 gamma rays and known nuclear data, cumulative fission-product yields were deduced for 69 fission products having half-lives between 36 seconds and 65 days representing 41 mass chains created during thermal-neutron fission of ${}_{}{}^{243}{}_{}{}^{}\mathrm{Cm}$.

We have followed the secondary projectile fragments of charges 3≤Z≤14 from Kr and Ar beams at 1.52A and 2A GeV with 647 and 669 secondary interactions, respectively, in nuclear emulsion. We do not observe any evidence for the anomalous fragments.

We have measured the Q value of the ${}_{}{}^{148}{}_{}{}^{}\mathrm{Gd}$(p,t${)}^{146}$Gd reaction by comparison with the ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$(p,t${)}^{63}$Cu calibration reaction. The ${}_{}{}^{148}{}_{}{}^{}\mathrm{Gd}$ target was fabricated from material produced in a Ta target. The tritons were analyzed with a quadrupole–dipole-dipole-dipole spectrometer. By combining the (p,t) Q value with the ${}_{}{}^{148}{}_{}{}^{}\mathrm{Gd}$ mass, we obtain -76 096±6 keV for the ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$ mass excess.

The static electric quadrupole moment Q${(2\mathrm{}}_1^{+}$) of the first excited state of ${}_{}{}^{136}{}_{}{}^{}\mathrm{Ba}$ and the reduced transition probability B(E${2;0}_1^{+}$→$2_1^{+}$) have been measured using the reorientation effect in Coulomb excitation. It is found that Q${(2\mathrm{}}_1^{+}$)=-0.19±0.06 (+0.07±0.07) e b and B(E${2;0}_1^{+}$→$2_1^{+}$) =0.419±0.004 (0.417±0.004) $e^2$${\mathrm{b}}^2$ for constructive (destructive) interference involving the second $2^{+}$ state. These results agree well with one of the previous measurements of these quantities, but disagree markedly with another which is of similar precision to the present work.

Exact finite-range distorted-wave Born approximation analyses of cross section and vector and tensor analyzing power angular distributions for some ${}_{}{}^{36}{}_{}{}^{}$,38Ar(d→,α) transitions induced by 16 MeV polarized deuterons have been performed using full sd-shell model wave functions and including a D-state amplitude for the α particle. The L-mixing ratios R for several unnatural parity transitions have been determined from comparisons of the calculations with the tensor analyzing power data. Shell-model calculations are found to be in agreement with the experimentally obtained phases of R, while the predicted magnitudes agree well in some cases.

We propose a semiclassical model based on one-body dissipation to describe the dynamics of symmetric and asymmetric fission. Shell effects are included by modifying the Randrup window formula. Results are compared to experimental data and to a static scission-point model.

The double-charge exchange reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${(}^{14}$C${,}^{14}$O${)}^{40}$ Ar is studied in terms of a two-step mechanism associated with the independent excitation of target proton and neutron pairing modes. Macroscopic pair-transfer form factors are employed in the coupled-channel analysis.

A Landau-Migdal approach to relativistic mean field theory of nuclear matter is used to define the single particle isoscalar current. By virtue of the near cancellation of scalar and vector potentials, this current is very close to the standard nonrelativistic isoscalar current; and hence the single particle isoscalar magnetic moment operator gives results in agreement with the nonrelativistic shell model. Calculations of magnetic moments for closed shell plus (or minus) one nucleon using this effective current operator recover the Schmidt values, thus resolving a longstanding problem with relativistic models of nuclear structure.

Because of its finiteness of boson expansion, the Dyson boson theory is known to allow one to calculate matrix elements in the boson space much easier than the Holstein-Primakoff Hermitian boson theory. The demerit of the Dyson boson theory is in the non-Hermiticity of the eigenvalue problem. Here it is shown that it is possible to make the eigenvalue problem Hermitian and to make the Dyson boson theory more manageable for practical use.

A parameter characterizing the forward-backward asymmetry of angular distribution is defined and its statistical features are discussed for a fluctuating pure compound nucleus cross section. It is shown that even for the energy averaged cross section a considerable asymmetry can appear with a significant probability.

We report results of a pion interferometry analysis for central collisions of 1.8 GeV/nucleon Ar on Pb at the Bevalac streamer chamber. The statistics are sufficient to allow a detailed study of the spatial structure of the pion emitting source. The dependence of the size of the source on the average magnitude of the momenta of the emitted pion pairs is consistent with the picture of an expanding pion source. There are also indications that the Ar nucleus is completely stopped by the Pb target in the most central collisions.