In particle physics, CP violation is a violation of CP-symmetry(or charge conjugation parity symmetry): the combination of C-symmetry (charge conjugation symmetry) and P-symmetry(parity symmetry). CP-symmetry states that the laws of physics should be the same if a particle is interchanged with its antiparticle (C symmetry) while its spatial coordinates are inverted (“mirror” or P symmetry). The discovery of CP violation in 1964 in the decays of neutral kaons resulted in the Nobel Prize in Physics in 1980 for its discoverers James Cronin and Val Fitch.

It plays an important role both in the attempts of cosmology to explain the dominance of matter over antimatter in the present Universe, and in the study of weak interactions in particle physics.

https://en.wikipedia.org/wiki/CP_violation