World’s biggest antimatter nucleus produced at Brookhaven

Ars Technica : The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory has produced the heaviest antimatter particle ever seen in a laboratory: antihelium-4, the antimatter partner of the alpha particle. Antihelium-3 was detected in the 1970s, but the antialpha has proved more difficult to spot. For a nucleus to condense, the right number of antimatter baryons of the right types must be traveling near enough to one another, with similar enough momenta. By colliding gold atoms, which each have 79 protons and 118 neutrons, RHIC increased the chances that antialphas would form. The discovery, published in Nature, will inform the search for antimatter elsewhere, including on the International Space Station. On 29 April the space shuttle Endeavour will begin a journey to the station to drop off the Alpha Magnetic Spectrometer, which will look for primordial antimatter.