GENEVA, Switzerland, July 5 (UPI) -- Europe's largest particle accelerator, the Large Hadron Collider, is back in action. According to two newly published studies, its latest round of experiments yielded three new "exotic" particles and confirmed the existence of a fourth.
The newly identified particles are considered "exotic" because they contain four quarks, the building blocks of all matter. Particle physicists used to believe all particles were composed of mesons, a quark-antiquark pair, or baryons, three quarks -- but no more than three quarks. A litany of discoveries have shown otherwise.