Scientists studying the tracks of particles streaming from six billion collisions of atomic nuclei at the Relativistic Heavy Ion Collider (RHIC) -- an 'atom smasher' that recreates the conditions of the early universe -- have discovered a new kind of antimatter nucleus, the heaviest ever detected. Composed of four antimatter particles -- an antiproton, two antineutrons, and one antihyperon -- these exotic antinuclei are known as antihyperhydrogen-4.
