Particle collision. Artist's impression of a proton-proton collision creating bosons. Such collisions are produced at the Large Hadron Collider (LHC) at CERN (the European particle physics laboratory) to test predictions in particle physics and high-energy physics. In July 2012 a proton-proton collision resulted in the creation of a particle consistent with the predicted Higgs boson. The particle was not seen, but was revealed through its decay products; a pair of Z bosons that each decayed into a pair of muons. In the Standard Model, the Higgs boson is used to explain why particles have mass.