Hot soup of super heavy antimatter

UC DAVIS (US) — Smashing gold together almost a billion times has resulted in the creation of the heaviest form of antimatter ever found.

Discovery of the antimatter equivalent of helium nuclei will help test theories of matter and antimatter, researchers say.

One of the fundamental puzzles of modern physics is to understand why, if matter and antimatter were created in the Big Bang in equal amounts and annihilate each other when they meet, there was enough matter leftover to make up the universe.

Using the Relativistic Heavy Ion Collider at the U.S. Department of Energy’s Brookhaven National Laboratory, physicists smashed gold particles into each other at almost the speed of light. The collisions briefly created a hot soup of subatomic particles called quarks and antiquarks, which then formed into new particles.

The research is reported in the journal Nature.

Sorting through data from almost a billion collisions, the research team found 18 examples of a stable antihelium-4 nucleus, made up of two antiprotons and two antineutrons.

“This is the heaviest antimatter anyone has ever created,” says Manuel Calderon de la Barca Sanchez, professor of physics at University of California, Davis. So far, the antihelium nuclei appear to have generally the same properties as regular helium, confirming existing theories.

If it were possible to “bottle” the antihelium particles, they would be as stable as regular helium, but, in practice, the particles fly through the accelerator until they hit a nucleus of regular matter and are annihilated.

“There is no process that we know that explains the amount of matter that we see in the universe,” Calderon says.

Understanding the rate at which anti-helium is produced could help physicists interpret other experiments, including an instrument soon to be delivered to the International Space Station to search for antimatter in deep space.

The collaborators plan a second 10-week run on the collider to produce more anti-helium particles this summer.

The research is supported primarily by the U.S. Department of Energy.

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