1. The problem statement, all variables and given/known data True/False: Because the potential between an electron and positron is identical to that of an electron and proton, if we compensate for the difference in mass, the differential scattering cross section in electron-proton scattering must be the same as for electron-positron scattering. Same question, but now for proton-proton scattering and proton-positron scattering. 2. Relevant equations 3. The attempt at a solution it seems like both of these statements have to be false. If electron-positron scattering were indistinguishable from electron-proton scattering with respect to their differential scattering cross section, how exactly do we experimentally probe things like the proton through electron-proton scattering experiments in order to discover the properties of the quarks? However, I don't know how to justify this intuition in a theoretical way. Does this have something to do with the difference between "equal mass scattering" vs "unequal mass scattering" that isn't accounted for when we say that we will account for the mass differences?