The Neutron Skin-Thickness of 208Pb Determined by Electron and Proton Scattering

Electron as well as proton elastic scattering is not able to determine the point proton and point neutron densities, ρ _τ (r), (τ =p,n), separately. If both scatterings are analyzed consistently, those densities would be determined uniquely, since the two densities are observed by different combinations from each other. Previous experiments have not provided ρ _τ (r) uniquely, but the values of the mean square radii of ρ ₚ(r), \, r²\, ₚ, and of ρ ₙ(r), \, r²\, ₙ, are shown to be determined consistently through the fourth moment of the observed charge density, \, r⁴\, c, in 208Pb. The previous analyses of (γ , π ⁰) and p̄-nucleus obtained a similar value of \, r²\, ₙ, but they do not yield the experimental value of \, r⁴\, c observed in electron scattering.