Particles that seem to come out of high-energy atomic collisions may have nothing to do with what was in the nuclei, but instead may be manufactured on the spot by the energy of the colliding particles. To avoid confusion about what came out and what was generated by the energy only, a group began probing nuclei using non-destructive low-energy electron beams on the order of 150 to 200 GeV. The shell structure of electrons, and the layered structure of hadronic particles begin to show up at these energies.
As indicated in the gold link this was predicted some time ago. We must use less energy to discover the electromagnetic structure of elementary particles. High energy beams blast right through the outer shells and only detect the more massive inner shells.
We ran across this article about a study that started back in the year 2000.
Doctor Robert Hofstadter of Stanford first suggested that nuclear particles
seemed to be made up of electrically charged shells. We sometimes say that
Robert Hofstadter received the Nobel Prize in Physics in 1961 for discovering the
structure of atomic nuclei. We would be more accurate to say that
Hofstadter's Nobel prize
was for discovering that atomic nuclei have structure. The scientific community
did not accept Hofstadter's shell-structure idea. These new findings are
beginning to show, however, that we may need to revisit