Fermi Coupling Constant

Discovered by: Enrico Fermi in 1933.

What is it? A coupling constant related to the Fermi interaction. The most precise experimental determination of the Fermi constant comes from measurements of the muon lifetime, which is inversely proportional to the square of G_F.

Why is it important? A fundamental constant of physics. 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.