In the 1960s, he proposed broken symmetry in electroweak theory. This explains the origin of mass of elementary particles in general. It also shows the origin of the W and Z bosons. The theory known as Higgs mechanism was proposed by several physicists at the same time. It proposes the existence of a new particle, the Higgs boson. On 4 July 2012, CERN announced they had found a new particle much like the Higgs boson in experiments, but that more work was necessary to analyse its properties and see if it had the properties expected from the Standard Model Higgs boson.