Fermi coupling constant

In particle physics, Fermi's interaction (also the Fermi theory of beta decay) is an explanation of the beta decay, proposed by Enrico Fermi in 1933. The theory posits four fermions directly interacting with one another (at one vertex of the associated Feynman diagram). This interaction explains beta decay of a neutron by direct coupling of a neutron with an electron, a neutrino (later determined to be an antineutrino) and a proton.

Fermi first introduced this coupling in his description of beta decay in 1933. The Fermi interaction was the precursor to the theory for the weak interaction where the interaction between the proton–neutron and electron–antineutrino is mediated by a virtual W⁻ boson.

Fermi first submitted his "tentative" theory of beta decay to the famous science journal Nature, which rejected it "because it contained speculations too remote from reality to be of interest to the reader." Nature later admitted the rejection to be one of the great editorial blunders in its history. Fermi then submitted the paper to Italian and German publications, which accepted and published it in 1933 in those languages, but it did not appear at the time in a primary publication in English (Nature finally belatedly republished Fermi's report on beta decay in English on January 16, 1939).

Fermi found the initial rejection of the paper so troubling that he decided to take some time off from theoretical physics, and do only experimental physics. This would lead shortly to his famous work with activation of nuclei with slow neutrons.

${\displaystyle \psi =\sum _{s}\psi _{s}a_{s},}$ where ${\displaystyle \psi }$ is the single-electron wavefunction, ${\displaystyle \psi _{s}}$ are its stationary states.

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