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Diagram Beta decay: beta particle is emitted from an atomic nucleus Compton scattering: scattering of a photon by a charged particle Neutrino-less double beta decay: If neutrinos are Majorana fermions (that is, their own antiparticle), Neutrino-less double beta decay is possible. Several experiments are searching for this. Pair production and ...
A Feynman diagram (box diagram) for photon–photon scattering: one photon scatters from the transient vacuum charge fluctuations of the other. Two-photon physics, also called gamma–gamma physics, is a branch of particle physics that describes the interactions between two photons. Normally, beams of light pass through each other unperturbed.
The Feynman diagrams are much easier to keep track of than "old-fashioned" terms, because the old-fashioned way treats the particle and antiparticle contributions as separate. Each Feynman diagram is the sum of exponentially many old-fashioned terms, because each internal line can separately represent either a particle or an antiparticle.
Electron–photon scattering generic Feynman diagram. The incoming target photon splits into a nearly collinear quark–antiquark pair. The impinging electron is scattered off the quark to large angles, the scatter pattern revealing the internal quark structure of the photon.
Both the scattering and annihilation diagrams contribute to the transition matrix element. By letting k and k' represent the four-momentum of the positron, while letting p and p' represent the four-momentum of the electron, and by using Feynman rules one can show the following diagrams give these matrix elements:
Feynman diagram of electron–positron pair production. One must calculate multiple diagrams to get the net cross section. The exact analytic form for the cross section of pair production must be calculated through quantum electrodynamics in the form of Feynman diagrams and results in a complicated function. To simplify, the cross section can ...
In quantum electrodynamics, there are two tree-level Feynman diagrams describing the process: a t-channel diagram in which the electrons exchange a photon and a similar u-channel diagram. Crossing symmetry , one of the tricks often used to evaluate Feynman diagrams, in this case implies that Møller scattering should have the same cross section ...
A Feynman diagram (box diagram) for photon-photon scattering, one photon scatters from the transient vacuum charge fluctuations of the other. Fluctuations