Which particle was discovered at CERN in 2012?

The particle discovered at CERN in 2012 was the Higgs boson.

On July 4, 2012, CERN announced that its ATLAS and CMS experiments had independently observed a previously unknown boson consistent with the Higgs boson. The particle is associated with the Higgs field, an energy field thought to permeate the universe. Interactions with that field help explain why many elementary particles have mass.

The discovery confirmed a key prediction of the Standard Model of particle physics. The theoretical mechanism was proposed in the 1960s by several physicists, including Peter Higgs and François Englert; Higgs and Englert received the 2013 Nobel Prize in Physics. CERN's Large Hadron Collider provided the high-energy collisions needed to produce and detect the particle indirectly through its decay products.

The Higgs boson is sometimes casually called the “God particle,” but physicists generally avoid that nickname. It is also not the same as a graviton, which remains hypothetical, or a neutrino, which had already been known for decades.