I'm currently reading about the parton model and deep inelastic scattering. As I've understood it was observed that when protons collided at high energy very little transverse momentum transfer was observed, while when electrons were collided with protons transverse momentum transfer was observed in accordance with treating the proton as if it were (or consisted of) an elementary charged fermion. I.e. the electron muon scattering formula captured the qualitative behavior of the scattering. According to the parton model (as explained in Peskin and Schroeder at page 476) this is explained by assuming that the proton is a loosely bound assemblage of partons; which are fermions carrying electric charge incapable of interchanging large momenta at high momentum transfer. However since these partons interact electromagnetically an electron can knock out a parton of the proton and this parton then exchanges momentum 'softly' with the rest of the proton, so that the pieces of the proton materialize as jets of hadrons. In my understanding this model has the theoretical support in QCD for which the strong coupling constant goes to zero asymptotically at large momentum transfer. This should thus explain why the proton constituents do not interact and thus why no transverse momentum transfer is observed. The problem I have with this picture is that these constituents are assumed to be charged; so why then do they not interact electromagnetically among themselves just as in the case with electron? Since they are charged should we not observe something like the electron muon scattering behavior also between the proton constituents? Why not?