Antihelium

In 1970, a more complex antinucleus, antihelium-3 (iHe), was discovered in the USSR.

In principle the energy should have been enough for the production of even heavier antinuclei. However, the probability for production of heavier masses is very tiny, and antihelium-3 is still the heaviest known antielement.

After several launches of their balloon, the scientists registered more than 40 million nuclei of helium in the cosmic rays, but not a single nucleon of antihelium.