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?