In the current standard model of particle physics (which does not account for the gravitational force), only one ingredient is yet to be directly discovered (the discovery of the tau neutrino the other missing particle was announced in July 2000). This elusive ingredient is known as the Higgs boson. The existence of the Higgs boson is indirectly predicted because most of the elementary particles have mass, which they could not have otherwise. The inclusion of the Higgs field in the standard model is an elegant solution of this problem.

The standard model of particle physics is a gauge field theory, meaning it is invariant under a certain set of symmetry transformations called gauge transformations. In effect, the gauge transformations allow the definitions of the fundamental objects of the theory (the matter fields) to be redefined differently at different points in space, without changing the observable physical effects...