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Up and strange

  1. Dec 2, 2011 #1
    Can an up quark absorb a negative W particle and become a strange quark? I know s can turn into u via the opposite process (emission of positive W), but can the interaction go the other way?

    This arises when trying to draw the Feynman diagram for the rather unlikely decay

    [tex]B^+\to D_s^++\bar{K^0}[/tex]
  2. jcsd
  3. Dec 2, 2011 #2


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  4. Dec 3, 2011 #3
    The process can always go both ways, as long as energy is conserved.
  5. Dec 3, 2011 #4
    Thanks. I guess then the only quark that could not be reached this way would be top quark, since its mass is so much larger than the mass of the W bosons.
  6. Dec 3, 2011 #5


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    An interesting question, related to this, was why experimentally the calculated rates of the process didn't match with the expected for a three quarks model, so a fourth quark, the charm, was postulated. See GIM mechanism.
  7. Dec 9, 2011 #6
    Hey, with enough accelerator energy everything is possible :wink: The top mass is 175 GeV, and the available energy at for example LHC ([itex]\sqrt{\hat{s}}[/itex] ) is probably a couple of TeV, i.e. many times the top mass

    Though you are correct in your reasoning, the transition amplitude between d and t quarks is a very small number, so transitions from down/strange to top are very unlikely. See Wiki: Cabibbo-Kobayashi-Maskawa matrix, the numbers to look for are non-diagonal ones in the third row, these describe transitions between top and lighter down-type quarks.
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