ZZ dibosons are rare pairs of Z bosons. They were first observed by the experiments at the Large Electron–Positron Collider (ALEPH, DELPHI, L3 and OPAL). The first observation in a hadron collider was made by the scientists of DØ collaboration at Fermilab. They are force-carrying particles produced in proton–antiproton collisions at the Tevatron, the world’s second highest-energy particle accelerator (after the CERN Large Hadron Collider). The observation of the ZZ dibosons was announced at a Fermilab seminar on 30 July 2008.