Answer: Antimatter nucleus
Notes: Scientists detected the heaviest antimatter nucleus, anti-hyperhydrogen-4, at the Relativistic Heavy Ion Collider (RHIC) in New York. The discovery came from over 6 billion collision events at the particle accelerator. This finding could help understand why the universe is mostly matter, despite equal creation of matter and antimatter during the Big Bang. Antimatter is like ordinary matter but with opposite electric charges, often called "mirror matter." Antimatter particles include positrons (positive electron counterparts), antiprotons, and antineutrons. Matter and antimatter annihilate each other on contact, releasing energy. Antimatter is created in particle accelerators and naturally occurs in the universe.
