- #1
eoghan
- 207
- 7
Hi there,
While reviewing the theory of Feynman diagrams for QED, a question came into my mind. In the textbooks, one usually deals with processes involving two incoming particles. But I could imagine a process where four particles are interacting (e.g. attached picture) and this can give a contribution that is of the same order as a loop diagram with only two interacting particles. Since in a collider two beams of particles collide I can expect to have interactions between any even number of particles. So in order to compute the cross section should one compute also these interactions? Or for some reasons the diagrams with more than two particles cancel away?
While reviewing the theory of Feynman diagrams for QED, a question came into my mind. In the textbooks, one usually deals with processes involving two incoming particles. But I could imagine a process where four particles are interacting (e.g. attached picture) and this can give a contribution that is of the same order as a loop diagram with only two interacting particles. Since in a collider two beams of particles collide I can expect to have interactions between any even number of particles. So in order to compute the cross section should one compute also these interactions? Or for some reasons the diagrams with more than two particles cancel away?