Why does the long-lived kaon only rarely decay to two pions?

[Gene Naden]

The weak interaction doesn't conserve CP, so it shouldn't care whether there are two neutral pions in the decay product or three. And the three-pion decay is slowed down by the lack of phase space since there is little mass in excess of that of three pions. So why don't we see more decays into two pions (like we do with the short-lived kaons)? Thanks.

 

[mfb]

CP violation of the weak interaction is small. It is not conserved exactly, but CP violating decays are still rare.

 

[Gene Naden]

Thank you for your quick and helpful response.