Energy-independent Optical Potential Research Articles

Meson-baryon dynamics in the nucleon-antinucleon system. I. The nucleon-antinucleon interaction.

A model for the nucleon-antinucleon interaction is presented, which is based on meson-baryon dynamics. The elastic part is the G-parity transform of the Bonn NN potential; annihilation is accounted for by microscopic baryon-exchange processes with two-meson intermediate states involving \ensuremath{\pi}, \ensuremath{\rho}, \ensuremath{\sigma}, \ensuremath{\omega}, \ensuremath{\delta}, K, and ${\mathit{K}}^{\mathrm{*}}$. Results for cross sections and polarization data are compared with a phenomenological treatment of annihilation based on a simple, state- and energy-independent optical potential.

Comments on the energy-independent optical potential

It is noted that the energy-independent optical potential yields both scattering and bound state solutions, and that this potential must be asymmetric to yield a spectroscopic factor different from unity.

Deep-lying hole states in the optical model

The strength function for deep-lying hole states in an optical potential is studied by the method of Green's functions. The role of isospin is emphasized. It is shown that, while the main trends of the experimental data on hole states in isotopes of Sn and Pd can be described by an energy independent optical potential, intermediate structures in these data indicate the specific nuclear polarization effects have to be included. This is done by introducing doorway states of good isospin into the optical model potential. Such states consist of neutron hole plus proton core vibrations as well as more complicated excitations that are analog states of proton hole plus neutron core vibrations of the parent nuclear system. Specific calculations for /sup 115/Sn and /sup 103/Pd give satisfactory fits to the strength function data using optical model and doorway state parameters that are reasonable on physical grounds.

The energy-independent optical potential and its physical interpretation

It is shown that the recently proposed energy-independent optical potential is in fact the abstract form of Feshbach's generalized optical potential appropriate for time-dependent scattering theory. Thus the concept carries no new physical content.

Energy-independent optical potentials

An energy-independent optical potential is derived by projection operator techniques. Its properties are investigated in a simple model.

General properties of energy independent nuclear optical model potentials

An energy independent optical potential for nucleon-nucleus scattering is formally derived. A simple relation between energy dependent and energy independent potentials is established showing that the latter has the same thresholds as the former. A generalized dispersion relation for energy independent potentials is found and compared to the conventional dispersion relation of the generalized energy dependent optical potentials.

Eikonal approach to dispersion corrections in elastic electron scattering

Dispersion corrections to elastic electron scattering are calculated using an eikonal approximation for the electron. Additional phase shifts Λ( b) with b = j + 1 2 /k can be defined which have to be added to the static phase shifts χ j obtained from a partial-wave calculation. Equivalent is a description by an energy-independent optical potential. Summation over the excited nuclear states is done by a special closure approximation. The only free parameterthe mean excitation energy — can be determined by the photo sum rule σ −2. Total inelastic cross sections agree well with experimental estimates; corrections in the elastic cross section are usually negative and small except in diffraction minima.