I was alerted by an important Particle Physics physicist on Robert Hofstadter results about the nucleon structure cited by me by means of the reference Rev. Modern Phys. Vol. 28, 214, 1956. He sent me the very important reference by R. Hofstadter, F. Bumiller and M. R. Yearian, Electromagnetic Structure of the Proton and Neutron (Rev. Modern Phys. Vol. 30(2), 482, 1958) in which details of the charge distribution around 0.2 fm are absent. His criticism had exactly to do with this fact. I recognize that I should have complemented my above reference and cited other references by Hofstadter and, more importantly, the interpretation by L Durand of Hofstadter results.
Going deeper into the matter, we can say that the charge distributions shown in this figure above are also due to the work of Robert R. Wilson (then at Cornell University) et al. and also in part due to the interpretation of Hofstadter results by L. Durand as shown in the paper by Robert A. Wilson, Electric Structure of Nucleons in which one finds a similar figure for the nucleons charge densities (Figure 5). This is also mentioned in the references of Robert Wilson paper:
 R. HOFSTADTER and R. HERMAN – Phys. Rev. Letters 6, 293 (1961); see, however, the reinterpretation of some of these results by L. DURAND, Phys. Rev. Letters 6, 631 (1961).
It is also important to take into account what R. Wilson says at the beginning of the above mentioned paper
“In an age of giant accelerators, of complex experiments and of mystifying theories it is a pleasure to report on some simple experiments, made with simple equipment and having a simple interpretation – simple, that is, if one doesn’t look too closely. The electron energies now available are about 1 Gev and the de Broglie wavelength of such electrons is about 0. 2 fermis, hence we can expect to make out some of the details of the proton and neutron.
Last year at the Rochester Conference, as a result of scattering experiments made at Stanford University [ 1] with their Linac and at Cornell University [ 2] with our electron synchrotron, we were both able to report the beginning of a detailed structure in that for large momentum transfers the electric and magnetic form factors were no longer nearly equal – as had previously been believed to be true for energies less than about 500 Mev.
During the past year, the measurements at Stanford ,  and at Cornell ,  have been considerably refined and extended.”
It is important to pinpoint that these experiments and their interpretations took place before the advent of the Quark Model. This means that the interpretations were not influenced by the Quark Model and are, thus genuine interpretations. I mention this to contrast it with the recent interpretations, completely biased by the Quark Model of point-like quarks in which the first peak of the proton charge distribution is shifted to higher r and the second peak does not appear. For example, the reader can take a look at the work by June L. Matthews Structure of the proton, neutron, and deuteron from scattering of polarized electrons by polarized gas targets.
I saw this above figure for the first time in the book Mechanics – Berkeley Physics course, vol. 1 (by C. Kittel, W. D. Knight, and M. A. Ruderman, McGraw-Hill Book company), in its Portuguese edition dated from 1965 by Editora Edgard Blücher, São Paulo, when I was an undergraduate Physics student at UFPE in the 1970’s (please, take a look at the section About Prof. M. E. de Souza) and I reproduce it below. In the Portuguese edition the figure is on page 429.
It is also important to pinpoint that the Nobel Prize committee which awarded the Nobel Prize to Robert Hofstadter took into account the fact of his findings on the internal structure of the nucleons when it said that the prize was “for his pioneering studies of electron scattering in atomic nuclei and for his thereby achieved discoveries concerning the structure of the nucleons”. But I dare to say that Robert Wilson should also have shared the prize.
I end this post saying that my work reconciles the Quark Model with Hofstadter and Wilson results and reveals that valence quarks are, actually, prequarks, and constituent quarks are the true quarks, and also solves many problems of Particle Physics. Please, take a look at other important posts in this web page such as False proof of valence quarks.
It is more than obvious that the internal structure which is common to both nucleons is the nucleon hard core seen by many different experiments and seen more recently by the TOTEM COLLABORATION.
It is also important to pinpoint that my work does not go against QCD, only shows that QCD is a sort of mean field theory that simplifies matters because, as it is easily grasped from these posts, primons are very complicated to be described. The Dirac equations for the two primons of each quark should be coupled equations and there are other complications. Therefore, QCD IS A GREAT THEORY AND WILL GO ON AS SUCH.
I was alerted by an important Particle Physics physicist on Robert Hofstadter results about the nucleon structure cited by me by means of the reference Rev. Modern Phys. Vol. 28, 214, 1956. He sent me the very important reference by R. Hofstadter, F. Bumiller and M. R. Yearian, Electromagnetic Structure of the Proton and Neutron (Rev. […]