From that data, its computers were able to positively identify 18 anti-alpha particles created.

FORBES: Scientists Detect Heaviest Known Antimatter Particle

The detector also enabled an analysis of the production rate of the anti-alpha particles, which was consistent with expectations.

FORBES: Scientists Detect Heaviest Known Antimatter Particle

Scientists working on the Alpha project at Cern are trying to find out by isolating and studying particles of anti-hydrogen.

BBC: The problem with anti-matter