Kaon-Box Diagram
© Wikimedia Commons, GNU Free Documentation License, Version 1.2. Author: Bambaiah, 22 June 2005.
This diagram shows the reactions by which neutral kaons oscillate between matter and antimatter states (
and 
). The discovery in 1964 that the reaction rates in the two directions differed implied that matter and antimatter behave differently—a factor that may have produced the excess of matter in our universe. (Unit: 1)