Kaons is correct
It jogged a memory, so I checked my copy of The Encyclopedia of Physics (2nd Ed., 1991), p.24 - the article on Antimatter.*
The principle was first proposed in 1967 by no less a figure than Andrei Sakharov. The citation given at the end of the article is: Sakharov, A.; JETP Lett.5, 24 (1967). It's a broken CP symmetry occurring at or before 10-35 sec, violating the conservation of baryon number. The asymmetric "residue", so to speak, is the normal matter of the Universe.
[see also p. 179, in the article on Conservation Laws, for a discussion of neutral kaon (Ko) decay modes, discovered in 1964]