A. Zee, Quantum Field Theory in a Nutshell · Problem II.6.2
Field Theory Redux
Physics — QFT
Problem
To order e2 the amplitude for positron scattering off a proton is just minus the amplitude (3) for electron scattering off a proton. Thus, somewhat counterintuitively, the differential cross sections for positron scattering off a proton and for electron scattering off a proton are the same to this order. Show that to the next order this is no longer true.