ABSTRACT
Some of the quanta of the weak fields have electric charge and ‘charged photons’ are simply not seen. This chapter implements gauge invariance in weak interactions by reconciling it with the massive gauge particles needed to generate the short-range force actually observed. The divergences which arise in the integration over loop momenta are determined by the large (Euclidean) momentum behaviour of the propagators and vertices appearing in any Feynman diagram. In general, therefore, some diagrams which are convergent with massless vector boson propagators will be divergent when massive vector boson propagators are substituted. In order to implement gauge invariance in weak interactions, gauge vector boson masses need to be generated without destroying the renormalisability of the gauge theory. Any such mass terms break the (gauge) symmetry, and the only known method of doing so in a renormalisable manner is called ‘spontaneous’ symmetry breaking.
