Which physicist discovered the positron in 1932 using a cloud chamber?

Carl D. Anderson discovered the positron in 1932 using a cloud chamber.

Anderson studied cosmic rays with a cloud chamber, a device that makes charged-particle tracks visible. He found tracks that curved like those of electrons but in the opposite direction in a magnetic field. The particle had the electron’s mass but positive charge, matching Paul Dirac’s predicted anti-electron.

Anderson called the new particle the positron. The discovery provided the first direct evidence of antimatter and earned him the 1936 Nobel Prize in Physics, shared with Victor Hess for cosmic-ray research.

The positron is the electron’s antiparticle. When a positron meets an electron, the pair can annihilate, producing energy, commonly including gamma rays. Anderson’s discovery is therefore foundational to both particle physics and medical imaging.