Year in review: Collider creates pentaquarks
New evidence clinches case for particle quintet
HIGH FIVE After analyzing 26,000 decays, a team at the Large Hadron Collider reported evidence for particles composed of five quarks (illustrated).
© CERN
Among the haul of subatomic particles discovered in 2015 are two quark quintets. Until recently, quarks, one of the fundamental units of matter, had been known to come only in clumps of three (to form such particles as protons and neutrons) or sometimes two.