You discovered CP violation!

CP Symmetry

C (Charge) and P (Parity) are discrete transformations that can be applied to a physical system.

If a theory is symmetric under C, then it works the same if all particles are exchanged with their antiparticles. If it has P-symmetry, then it is invariant under inversion ("mirroring") of all spatial coordinates

For a long time, physicists believed that all of physics is invariant under the combination CP of both symmetries. It turned out that this is wrong, as was discovered by Cronin, Fitch et al. in 1964 when they studied the decay of the neutral K meson.

CPV in the Kaon System

In 1964, Cronin, Fitch, et al. showed that CP symmetry is broken in the decay of the long-lived neutral K meson.

If all of physics was invariant under CP transformation, then this long-lived version of the K meson would never decay into two pions.

However, this kind of decay was discovered!

You can see their results on the left: In the middle plot (the one relevant for K-meson decays), a clear excess is recognizable.

For their discovery, Cronin and Fitch received the Nobel Prize in Physics in 1980.

Resources

• The original publication by Cronin, Fitch et al.
• Wikipedia on CP violation
• Neutral kaon mixing on Wikipedia