Proton Distribution Radii of 16–24O: Signatures of New Shell Closures and Neutron Skin

The root mean square radii of the proton density distribution in 16–24O 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 22–24O despite 22,24O 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 ab initio calculations employing the chiral NNLOsat interaction, though skin thickness predictions are challenged. Furthermore, shell model predictions agree well with the data.