Despite the numerous successes of the Standard Model (SM), it cannot describe many experimental facts - the existence of dark matter, the problems of naturalness and other.
One of the main task for experiments on LHC is to find the ways how to extend the SM. It could be searches of new resonances or symmetries, deviations from SM predictions.
ATLAS (CERN, Geneve, Swiss) is one of the biggest detector of the world. It is multipurpose devise to study huge amount of different reactions. All studies are realized by multinational groups.