A hypothetical subatomic particle postulated to account for the rarity of processes that break charge-parity symmetry. It is very light, electrically neutral, and pseudoscalar.
- ‘Or another candidate is an even more exotic particle called the axion.’
- ‘Axions, if they exist at all, do so in our ordinary dimensions, but they are stable neutral particles.’
- ‘This has helped to promote particle-DM, with candidates such as axions, neutralinos and other cold DM particles, as well as warm DM, and self-interacting DM, whose nature is not even specified.’
1970s: from axial + -on.