Kaon discovered by the unusual fork

[nonequilibrium]

Kaon discovered by "the unusual fork"

So historically (reading about it in Griffiths) the (neutral) kaon was discovered by noting that there was some neutral particle decaying into a positive and neutral pion.

But how did they know at the time (1947) that it was not the neutron doing this? Of course now we know this is not possible due to, say, baryon number. But how did they know it wasn't the neutron at the time. The only thing I can think of is that the kaon lifetime is shorter than the neutron's. Is that it?

 

[mfb]

Neutrons are "stable" in accelerator experiments - while you might see a decay from time to time, usual flight times are measured in nanoseconds, while the lifetime of the neutrons is several minutes.
In addition, if you can measure the momentum of the charged and neutral pion, you can reconstruct the mass of the decayed particle.

there was some neutral particle decaying into a positive and neutral pion.

Charge conservation? Do you mean positive+negative pion?

 

[nonequilibrium]

Yes, sorry, I meant negative.

And thanks for the answer.

 

[Vanadium 50]

Furthermore, the decay you discuss, called K2pi, has only the two pions in the final state; if one measured the momentum of those pions and calculated the mass of the parent, oine always got about 500 MeV, half of the neutron's mass. That demonstrates that it's not neutrons.