Hadron

A composite particle made of two or more quarks. There are two sub-categories of hadrons: “baryons”, such as protons and neutrons, are made of three quarks (or three anti-quarks), while “mesons” are made of a quark and an anti-quark. Atomic nuclei can also be considered hadrons, since they are also fundamentally made of quarks. The LHC collides two species of hadrons: protons and lead nuclei (also called lead ions). Hadrons produced in collisions typically cluster together to form particle jets in the detectors.