A quark–gluon plasma (QGP) or quark soup is a (possible) phase of quantum chromodynamics (QCD) which exists at extremely high temperature and/or density. This phase consists of asymptotically free quarks and gluons, which are several of the basic building blocks of matter. Experiments at CERN's Super Proton Synchrotron (SPS) first tried to create the QGP in the 1980s and 1990s: the results led CERN to announce indirect evidence for a "new state of matter" in 2000. Current experiments (2011) at the Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) at Long Island (NY, USA) and at CERN's recent LHC collider at Geneva (Switzerland) are continuing this effort, by smashing relativistically accelerated gold ions—at LHC, lead ions—into each other.