Physicists at the Relativistic Heavy Ion Collider (RHIC) in New York say they have created nuclei of antihelium-4 for the first time – the heaviest antimatter particles ever seen on Earth. Antimatter ...

Curiously, for each antihelium nucleus with two antineutrons, an isotope called antihelium-4, there were two with a single antineutron: antihelium-3.

Composed of four antimatter particles -- an antiproton, two antineutrons, and one antihyperon -- these exotic antinuclei are known as antihyperhydrogen-4.

Composed of four antimatter particles — an antiproton, two antineutrons, and one antihyperon — these exotic antinuclei are known as antihyperhydrogen-4.

Matter and antimatter appear to be perfect mirror images of each other, scientists have discovered with unprecedented levels of precision.

Physicists have detected the heaviest antimatter atoms, bolstering antimatter theories and the search for dark matter.

These nuclei are like regular helium nuclei, except that instead of having two protons and two neutrons, they have two negatively charged antiprotons and two antineutrons.

Scientists at Brookhaven National Laboratory on Long Island, N.Y., have discovered the heaviest antimatter ever observed. It's antihelium-4, a conglomeration of two antiprotons and two antineutrons.

There are also neutral antineutrons. And if any of these particles touch their antiparticles—if, say, an electron touches a positron—they annihilate each other in bursts of energy.