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Kaon discovered by the unusual fork

  1. Jun 26, 2012 #1
    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?
  2. jcsd
  3. Jun 26, 2012 #2


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    Re: Kaon discovered by "the unusual fork"

    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.

    Charge conservation? Do you mean positive+negative pion?
  4. Jun 26, 2012 #3
    Re: Kaon discovered by "the unusual fork"

    Yes, sorry, I meant negative.

    And thanks for the answer.
  5. Jun 26, 2012 #4

    Vanadium 50

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    Re: Kaon discovered by "the unusual fork"

    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.
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