Tetraquarks could help physicists understand the universe’s first generations of matter
The rediscovery of an exotic particle provides the best evidence yet that quartets of quarks exist in a universe dominated by two- and three-quark matter.
By validating the particle’s existence, says lead author Tomasz Skwarnicki, a physicist at Syracuse University in New York, “we are automatically proving that four-quark states exist.”
Quarks, one of the fundamental constituents of matter, never exist on their own. Held together by particles called gluons, quarks and their antimatter counterparts, antiquarks, cluster in threes to form baryons (including protons and neutrons) and in pairs to produce mesons (including pions and kaons).
But in 2003, physicists at the Belle particle collider in Japan discovered a bizarre particle called X(3872) that didn’t seem to fit in either category. Based on its mass (3,872 million electron volts) and the particles it decayed into, X(3872) appeared to consist of a charm quark, an anticharm and at least