Radii Of Neutron Distributions Research Articles

Neutron distributions from pionic atoms

Abstract The radii of neutron distributions in nuclei are extracted from experimental shifts and widths of pionic atoms. A best fit to pionic-atom data is carried out by varying simultaneously the neutron radii and the parameter of a pion-nucleus optical potential. We have used three different potentials: one of them theoretical plus a small phenomenological part, another one semiphenomenological, with the linear terms in the density obtained from experimental πN amplitudes and the quadratic terms fitted to the pionic-atom data, and a third one purely phenomenological, obtained from a direct fit to pionic-atom data. The radii obtained with all of them are remarkably close and also close to the Hartree-Fock values. The combined statistical and systematic errors of the neutron mean-root-square radii are smaller than 0.2 fm for light and medium nuclei and smaller than 0.1 fm for heavy nuclei.

On radii of neutron distributions in nuclei

Abstract We consider the analyses of the differences between rms radii (Δ = rn − rp) of neutron and proton distributions in a wide variety of nuclei. We note that apart from its own intrinsic interest, the quantity Δ is of importance for isotope shifts, core polarization contributions to the Coulomb energy differences of mirror pairs (Nolen-Schiffer anomaly) and the renormalization of the effective interaction. For example, if Δ were very small in 48Ca then the Nolen-Schiffer anomaly could be explained by a core polarization mechanism. We consider critically the various methods of determining Δ and conclude that at present probably the most reliable method is high energy (≈ 1 GeV) proton-nucleus scattering. The different theoretical analyses based upon, e.g., the multiple diffraction theory (where Glauber amplitude is the leading term) or the optical potential (KMT) formalisms appear to be converging to essentially the same answer when analyzing the same data. High energy α-particles and medium energy pions can also become useful sources of information if higher order optical potentials are treated with care. We find that Δ is rather large in 48Ca, i.e. there is a neutron skin, so that the Nolen-Schiffer anomaly cannot be explained by a core polarization mechanism. The results of high energy proton-nucleus scattering are in excellent agreement with current density dependent Hartree-Fock calculations.

Radius of neutron distribution in lead

Radius of neutron distribution in lead