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Higgs boson research. Graphic of a transverse section through a detector showing a collision event recorded during the search for the Higgs boson. This event (a proton-proton collision) was recorded with the CMS (Compact Muon Solenoid) detector in 2012. It shows characteristics expected of a ZZ event, the decay of the Standard Model's Higgs boson to a pair of Z bosons. One of the Z bosons decays to a pair of electrons (green lines and green towers) and the other decays to a pair of muons (red lines). In the Standard Model, the Higgs boson is used to explain why particles have mass. CERN (the European particle physics laboratory) announced the Higgs boson discovery on 4 July 2012. (KEYSTONE/SCIENCE PHOTO LIBRARY/THOMAS MCCAULEY, LUCAS TAYLOR/CERN/SCIENCE PHOTO LIBRARY)