ABSTRACT
Fermi always said that his weak interaction theory of 1937 was inspired by quantum electrodynamics (QED). In QED, the basic interaction involves an electron going into an electron plus a photon; Fermi had a neutron going into a proton, with the emission of an electron and an antineutrino. us, the combination of the electron with the antineutrino played the role of the photon. Also in the 1930s, a dierent analogy with QED was suggested by Felix Klein. Consider the diagram in Figure 8.1a, in which an electron near a nucleus produces a positron-electron pair due to the exchange of a virtual photon. e analogue is Figure 8.1b, where the virtual photon is replaced by a new particle, a charged boson W-. en, the fundamental interaction, like in QED, involves a vertex with just three particles: fermion-fermion-boson.
