Antimatter particles detected on the International Space Station (ISS) may be evidence for unknown physics, new research suggests.
The particles, antimatter versions of helium nuclei, may have been produced by cosmic fireballs, — and physicists can't explain how those fireballs formed using the Standard Model, the theory which describes the zoo of subatomic particles.
All elementary particles have corresponding antiparticles with opposite electric charges, which annihilate each other on contact. Theory suggests half the matter in the universe should have been antimatter, which would mean the universe would have destroyed itself soon after the Big Bang.
Yet antimatter in the universe is scarce and fleeting. While particle accelerators can generate antiparticles through collisions of protons and electrons, and special detectors observe antiparticles from high-energy space collisions, such as those from supernova explosions, these usually yield only single antiparticles like positrons (antielectrons) and antiprotons.
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However, about eight years ago, the Alpha Magnetic Spectrometer (AMS-02) aboard the ISS detected around 10 antihelium nuclei. These nuclei consisted of two antiprotons and either one or two antineutrons (for antihelium-3 and antihelium-4 versions, respectively). If confirmed through further analysis, the discovery would challenge the Standard Model of particle physics
According to the Standard Model, making antihelium-4 requires that at least three or four antiprotons and antineutrons be near enough to each other and be moving slowly enough to stick together, study co-author Michael A. Fedderke, a postdoctoral researcher at the Perimeter Institute for Theoretical Physics in Canada, told Live Science in an email. Based on these requirements, one antihelium-4 would be produced for every 10,000 antihelium-3.