J.G. Zabolitzky

Momentum distributions of nucleons in nuclei

Abstract We present a microscopic evaluation of nuclear momentum distributions for the ground states of 4 He and 16 O. The momentum distribution is the sum of a single particle part and a correlation part. Beyond a momentum of 2 fm −1 the correlation part becomes dominating and exceeds the single particle part by arbitrary orders of magnitude for sufficiently high momenta. Even a quite crude experimental determination of momentum distributions would yield extremely useful information on nuclear correlations.

Solution of the generalized Brueckner-Hartree-Fock (BHF) equations in the exp(S) formalism

Abstract The angular momentum reduction of the generalized BHF equations is performed and the iterative schemes and numerical methods employed in the solution of the resulting set of equations are outlined. In addition, the treatment of the coupling terms to the Bethe-Faddeev equations is described.

The solution of the three-particle Bethe-Faddeev equation for finite nuclei

Abstract The solution of the three-body equation obtained within the framework of the exp( S ) formalism is described and numerical results are given for Faddeev-Brueckner-Hartree-Fock (FBHF) calculations on the nuclei 4 He and 16 O. The convergence of the cluster expansion is discussed.

Charge form factors of doubly closed shell nuclei

Abstract Charge form factors of the doubly closed shell nuclei 4 He, 16 O and 40 Ca are calculated by the use of Brueckner-Hartree-Fock (BHF) and Faddeev-Brueckner-Hartree-Fock (FBHF) manybody wave functions with an approximate treatment of three-body forces. Meson-exchange-current-contributions to the form factors are discussed in detail within the same framework. These currents are shown to be especially important in the case of 4 He.

Triple self consistent solution of the three-particle Bethe-Faddeev and Brueckner-Hartree-Fock equations

Abstract Completely self consistent Brueckner-Hartree-Fock (BHF) calculations with inclusion of the three-particle Bethe-Faddeev (BF) amplitudes have been performed on 4 He and 16 O both for the Reid-soft-core (RSC) and Tourreil-Sprung super-soft-core (SSC) potential. Binding energies and root mean square radii come out better than with parameter free BHF-type calculations. We coin the name FBHF (3) (Faddeev-Brueckner-Hartree-Fock) for this type of calculation.

A first step towards realistic calculations of parity-mixing effects in heavy nuclei

Abstract As an example the circular polarization of the 482 keV line in 181Ta is calculated using semi-microscopic description of the nucleus (independent particle model with the effective residual interactions of the pairing plus quadrupole and octupole types) and taking into account short-range correlations via the generalized Bethe-Goldstone equation. The results obtained for various strong and weak nucleon-nucleon potentials are far away from agreement with other calculations done up to now. No weak interaction theory seems to be able to explain the experimental values.

Theory of the effective interaction in nuclei

Abstract Extending the coupled-cluster many-body method we present ab initio calculations of the effective interaction in nuclei neighbouring 16 O. The convergence problems encountered in previous approaches are overcome by means of three-body Bethe-Faddeev summations included fully self-consistently. The results for mass 15 to 18 nuclei are in agreement with experiment to within the uncertainties due to insufficient knowledge of the bare nucleon-nucleon interaction and neglect of mesonic and isobaric degrees of freedom.

Short-range correlations and parity impurities

Abstract Two problems arising in calculating parity-violating effects in nuclei are discussed: the lack of reliable information on (i) weak parity-violating NN potentials and (ii) strong NN potentials at short relative distances and their influence on nuclear structure (short-range correlations). It is shown how to compute the latter reliably with the result that the parity admixtures depend strongly on the nucleon-nucleon potentials used. From this we conclude that the determination of the weak NN forces cannot be separated from the determination of the short-range behaviour of strong NN potentials.

Negative parity states in 16O from coupled-cluster equations

Abstract The extension of the coupled-cluster theory to excited states of closed-shell nuclei is presented. The method is applied to the negative parity particle-hole spectrum of 16 O. Some approximations found necessary in the application of the theory at the three-body level are discussed. Numerical calculation bears out characteristic discrepancies to experimental energy levels for some T = 0 states whereas agreement with experiment is found for T = 1 states.

On the ground-state of the alpha-particle and verification of the coupled-cluster method

Abstract A coupled-cluster calculation for the alpha particle is found to agree to three significant digits for energy and radius with a previous, exact solution of the Schrodinger equation for the same hamiltonian by means of the Greens-function Monte Carlo method. Various implications of this finding are discussed.