Since a Kaon's wavefunction is composed of $K_S$ and $K_L$ which are CP-even and CP-odd respectively. The Kaon can decay into $\pi \pi \pi \pi$ through $K_S$ since the 4 pions have CP-parity $= (-1)^4 = 1$

Is this just like the explanation as to why it can decay into 2 pions?

Also, any recommendations on another book for particle physics other than Griffiths? It is really bad.

  • $\begingroup$ There's a list of other books here. At this level I think Griffiths has the clearest explanations by far, though. There are even clearer books, but they're pitched at a much higher level. $\endgroup$
    – knzhou
    Commented Mar 8, 2018 at 11:04

1 Answer 1


A K0 has a mass of ~497 MeV. The pion ~140 MeV.

Four pions 4x140=560 MeV. Thus four pions cannot in any way be produced from the rest mass of a K0, even if all four are at rest.


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