Radioactive Beta Decay of the Neutron
... Classic Weak Interaction
neutron (udd) -> proton (uud) + electron + e-antineutrino
decay electrons initially called "beta rays"
       ...didn't know they were electrons                            Neutron                                                  -1/3= +2/3 -1                         Proton      +  Virtual W^-  boson                                               Proton     +      Electron + Antineutrino

intermediate stages occur in <10^-27 second...not observable
  ....see Feynman graph