34139540
Shape of the beta spectra in the A=14 system.
35977510
Quadrupole moments of sd-shell nuclei.
Shell-model calculations are presented for electric quadrupole moments of A = 17-39 nuclei. The shell-model wave functions, which span the complete 0d/sub 5/2/-ls/sub 1/2/-0d/sub 3/2/ model space in all instances, are obtained by diagonalizing an sd-shell Hamiltonian which consists of a fixed single-particle energy spectrum and a single set of two-body matrix elements scaled as a function of the mass number A. Results obtained with harmonic oscillator and Saxon-Woods single-particle radial wave functions and matched effective-charge models are presented for ground states of odd-even and doubly odd nuclei and for J/sup ..pi../ = 2/sup +/ first-excited states of doubly even sd-shell nuclei.
19689278
Diproton decay of nuclei on the proton drip line.
The process of direct two-proton decay of nuclei with {ital Z}=22--28 on the proton drip line is considered. On the basis of new 0{ital d}{sub 3/2}-0{ital f}{sub {ital f}/2} shell-model mass extrapolations, {sup 39}Ti, {sup 42}Cr, {sup 45}Fe, {sup 48}Ni, and {sup 49}Ni are found to be bound to single-proton decay but unbound to two-proton decay. New estimates of the spectroscopic factors and lifetimes have been made. The decays of {sup 39}Ti, {sup 45}Fe, and {sup 48}Ni are found to be promising for further experimental investigation.
35625352
Status of the nuclear shell model
In this review we concentrate on recent results of shell model calculations and related experimental data obtained for the sd-shell nuclei. Model spaces and effective interactions, Gamow-Teller, magnetic dipole, electric quadrupole, and higher multipole matrix elements, and electron scattering form factors are discussed. (AIP)
33560005
Gamow-Teller beta-decay rates for A <= 18 nuclei.
A comprehensive analysis is made of the experimental information on Gamow-Teller beta decay for the light (A\ensuremath{\le}18) nuclei. Experimental data on half-lives, Q values, and branching ratios are tabulated. Experimental logft values and beta-decay matrix elements are deduced from these data. The one-body-transition densities necessary to predict the beta-decay matrix elements are then calculated using a recently constructed shell-model Hamiltonian operating in the first four major shells. Using these parameters, effective Gamow-Teller operators are deduced for the 0p shell from a least-squares fit to 16 experimental matrix elements. The effective operators are used to calculate 83 decay matrix elements. Some specific decays are discussed.
39044560
Neutron halos in the Na isotopes.
The neutron and proton density distributions of the Na isotopes out to the proton and neutron drip lines are calculated in the spherical Hartree-Fock model with a wide variety of density-dependent Skyrme interactions. The results are compared to recent experimental data for the interaction cross sections and for the rms radii. We discuss the role of the deformed intruder states and the problems associated with predicting the location of the neutron drip line for this mass region. {copyright} {ital 1996 The American Physical Society.}
15583656
Black hole pair creation and the entropy factor.
It is shown that in the instanton approximation the rate of creation of black holes is always enhanced by a factor of the exponential of the black hole entropy relative to the rate of creation of compact matter distributions (stars). This result holds for any generally covariant theory of gravitational and matter fields that can be expressed in Hamiltonian form. It generalizes the result obtained previously for the pair creation of magnetically charged black holes by a magnetic field in Einstein--Maxwell theory. The particular example of pair creation of electrically charged black holes by an electric field in Einstein--Maxwell theory is discussed in detail.
28110065
Kaon production from hot and dense matter formed in heavy-ion collisions.
In heavy-ion collisions, kaons can be produced from baryon-baryon, meson-baryon, and meson-meson interactions. Simple meson-exchange models are introduced to study kaon production from these processes in the free space. These models are then extended to determine kaon production in hot, dense nuclear matter by taking into account the decreasing hadron masses as a result of the restoration of chiral symmetry and the condensation of kaons. We find that the cross sections for kaon production from all three processes are enhanced. In particular, the effect of decreasing hadron masses on kaon production from the meson-meson annihilation is most significant. In the hydrochemical model for heavy-ion collisions, we demonstrate that the observed enhancement of kaon yield in high-energy heavy-ion collisions can be explained if the medium effect is included.
28894226
Proton-nucleus scattering and density dependent meson masses in the nucleus.
The influence of density dependent meson masses, proposed in many previous papers, on proton-nucleus scattering in the several hundred MeV region is investigated. Introduction of this density dependence is found to remove the nuclear radius discrepancy which persistently occurred in analyses with the nonrelativistic impulse approximation when empirical nuclear densities obtained from electron scattering were employed. Nonlocality, suggested by earlier derivations of the density dependent masses, had to be introduced. Taking the estimated range of nonlocality from the earlier calculations, agreement with experiment was significantly improved by this introduction. Effects on the spin-orbit interaction and imaginary part of the optical model are qualitatively discussed. The density dependent meson masses aid in increasing the strength of the spin-orbit interaction. Preliminary results calculated in a relativistic impulse approximation (IA2) formalism for the spin observables are shown and discussed.
668564
Medium effects on kaon and antikaon spectra in heavy-ion collisions.
In the linear chiral perturbation theory, both kaon and antikaon masses decrease in dense matter. There is also a repulsive vector potential for the kaon and an attractive one for the antikaon. With these effects included in the relativistic transport model, it is found that the slope parameter of the kaon kinetic energy distribution is larger than that of the antikaon. This is consistent with the experimental data from heavy-ion collisions in the Alternating Gradient Synchrotron experiments at Brookhaven.
8309896
Photonuclear fission from high energy electrons from ultraintense laser-solid interactions
A new regime of laser-matter interactions in which the quiver motion of plasma electrons is fully relativistic, with energies extending well above the threshold for nuclear processes, is studied using a petawatt laser system. In solid target experiments with focused intensities exceeding 10(20) W/cm(2), high energy electron generation, hard bremsstrahlung, and nuclear phenomena have been observed. We report here a quantitative comparison of the high energy electrons and the bremsstrahlung spectrum, as measured by photonuclear reaction yields, including the photoinduced fission of 238U.