Proton Distribution Radii of ^{16-24}O: Signatures of New Shell Closures and Neutron Skin.

Abstract

The root mean square radii of the proton density distribution in ^{16-24}O derived from measurements of charge changing cross sections with a carbon target at ∼900A MeV together with the matter radii portray thick neutron skin for ^{22-24}O despite ^{22,24}O being doubly magic. Imprints of the shell closures at N=14 and 16 are reflected in local minima of their proton radii that provide evidence for the tensor interaction causing them. The radii agree with abinitio calculations employing the chiral NNLO_{sat} interaction, though skin thickness predictions are challenged. Shell model predictions agree well with the data.