The Large Hadron Collider (LHC) is also a big hadron discoverer. The atom smasher near Geneva, Switzerland, is most famous for demonstrating the existence of the Higgs boson in 2012, a discovery that slotted into place the final keystone of the current classification of elementary particles. But the LHC has also netted dozens of the non-elementary particles called hadrons—those that, like protons and neutrons, are made of quarks.
The latest hadron made its debut at the virtual meeting of the European Physical Society on 29 July, when particle physicist Ivan Polyakov at Syracuse University in New York unveiled a previously unknown exotic hadron made of four quarks. This brought the LHC’s hadron bounty up to 62 according to a tally kept by Patrick Koppenburg, a particle physicist with Nikhef, the Dutch National Institute for Subatomic Physics in Amsterdam. “These are all world firsts,” says Koppenburg, who is based at CERN, the European particle-physics laboratory that hosts the LHC.
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