23/05/2019
What is the universe made of? This question has puzzled humanity since Ancient Greece. One of the fundamental building blocks of nature are quarks, which are bound inside protons and neutrons, making a large part of our known universe. For a long time quarks have been seen only when combined in triplets or in pairs. Recent observations at the Large Hadron Collider (LHC) at CERN suggest that there exist also particles made of four and five quarks. The true identity of these new particles, however, remains a mystery: Are they made of quarks tightly bound together? Or, are we seeing a sort of subatomic molecule? Physicists at the LHC are working to answer these questions.