The decay of one type of \({\rm{K}}\)-meson is cited as evidence that nature favours matter over antimatter. Since mesons are composed of a quark and an antiquark, is it surprising that they would preferentially decay to one type over another? Is this an asymmetry in nature? Is the predominance of matter over antimatter an asymmetry?

Generally, the matter is made up of matter but every matter contains constituent antimatter particle. The decay of one K-mesons preferentially creates matter over antimatter.

Matter and antimatter should be equivalent pairs of opposing quantum numbers, just as a positive charge is neither better nor worse than a negative charge. This is why we expect a K-meson, especially a long-lived neutral kaon composed symmetrically of a quark-antiquark, to decay with equal probability into a "matter heavy" path and a "antimatter heavy" path. This was not noticed. With a higher probability, the -meson decays into the "matter heavy" path.

This was the first indication of a violation of CP symmetry. Because CP symmetry states that the physics should be the same in both C-symmetry (particle-antiparticle interchange) and P-symmetry (parity change, coordinate inversion) at the same time, its violation is important in attempts to explain the predominance.