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Pair production and annihilation: In the Stückelberg–Feynman interpretation, pair annihilation is the same process as pair production: Møller scattering: electron-electron scattering Bhabha scattering: electron-positron scattering Penguin diagram: a quark changes flavor via a W or Z loop Tadpole diagram: One loop diagram with one external leg
Pair production often refers specifically to a photon creating an electron–positron pair near a nucleus. As energy must be conserved, for pair production to occur, the incoming energy of the photon must be above a threshold of at least the total rest mass energy of the two particles created. (As the electron is the lightest, hence, lowest ...
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This expression can be derived by using a quantum mechanical symmetry between pair production and Bremsstrahlung. Z {\displaystyle Z} is the atomic number , α f i n e ≈ 1 / 137 {\displaystyle \alpha _{fine}\approx 1/137} the fine structure constant , ℏ {\displaystyle \hbar } the reduced Planck constant and c {\displaystyle c} the speed of ...
To create an electron-positron pair, the total energy of the photons, in the rest frame, must be at least 2m e c 2 = 2 × 0.511 MeV = 1.022 MeV (m e is the mass of one electron and c is the speed of light in vacuum), an energy value that corresponds to soft gamma ray photons.
This fermion pair can be leptons or quarks. Thus, two-photon physics experiments can be used as ways to study the photon structure, or, somewhat metaphorically, what is "inside" the photon. The photon fluctuates into a fermion–antifermion pair. Creation of a fermion–antifermion pair through the direct two-photon interaction.
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In physics, mean free path is the average distance over which a moving particle (such as an atom, a molecule, or a photon) travels before substantially changing its direction or energy (or, in a specific context, other properties), typically as a result of one or more successive collisions with other particles.