A family of related, exotic particles, each made up of four quarks, has been discovered. The finding could hold clues about the evolution of the universe, the researchers said.
The four newfound tetraquarks, now called X(4140), X(4274), X(4500) and X(4700), each are composed of two quarks and two antiquarks (the antimatter partners of quarks). Yet each of the newfound particles has a different mass and different subatomic properties. They are considered a family of tetraquark siblings because of having the same quark composition and arrangement.