Core polarization effects in sd-shell nuclei and charge-symmetry breaking in the nuclear mean field.

Abstract

The proton and neutron densities and nuclear potentials are calculated for the deformed sd-shell nuclei /sup 28/Si and /sup 32/S in the framework of the constrained Hartree-Fock method and compared with the results of the spherical nucleus /sup 40/Ca. Coulomb core polarization effects are responsible for differences in the proton and neutron Hartree-Fock potentials. These charge-asymmetry effects in the nuclear mean field must be taken into account when trying to decide whether the charge asymmetry observed in proton and neutron scattering is due to a genuine charge asymmetry in the nuclear force and, if possible, to put an upper limit on the magnitude of this effect. Our calculations indicate that there is no enhancement of the charge asymmetry due to nuclear deformation. The often proposed volume integral of the nuclear potential is found not to be an appropriate tool to investigate charge-asymmetry effects in nuclei due to a large cancellation in the integral.