Observation of an Antimatter Hypernucleus

Forming Antimatter Nuclei Atomic nuclei are everywhere and form all the matter visible to us in the universe. Their counterparts, however—antinuclei or antimatter—are relatively shy about making an appearance. Chen et al. (p. 58 published online 4 March; see the Perspective by Cohen ) used the Relativistic Heavy-Ion Collider to coax them into existence by colliding high-energy beams of gold ions head-on. Within the debris from the collisions, evidence was found in the decay paths and particle tracks that suggested the formation of nuclei from antimatter. The ability to form these exotic particles in abundance should help to probe fundamental aspects of nuclear physics, astrophysics, and cosmology.