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Homework Help: Show that there is no d → s + Z^0

  1. May 26, 2016 #1
    1. The problem statement, all variables and given/known data
    Consider weak interactions of quarks involving the Z0 bosons. Show that there is no d → s + Z0 interaction in the Standard Model.

    2. Relevant equations
    (d') = (cosθ sinθ) (d)
    (s') (-sinθ cosθ) (s)
    This is the change of variables matrix.
    θ is the Cabibbo angle, with the rotation matrix on the down and strange quark

    3. The attempt at a solution
    I'm not sure how to prove this, I think it may be something to do with that there is a sinθ x both d and s if you're doing the transformation so they're both suppressed? But that's a wild guess, my knowledge isn't that deep on this matter.
    Thank for any help, much appreciated!
  2. jcsd
  3. May 27, 2016 #2


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    2017 Award

    Staff: Mentor

    Which course is this?

    The nonexistence of this interaction (at tree-level) is an experimental result. Sure, you can look at equations and point out that it does not happen according to them (the standard model Lagrangian is probably the best point), but those equations were made to reflect our measurements, so that's kind of recursive reasoning.
  4. May 27, 2016 #3
    It's a particle physics module in a 2nd year physics degree, I had the exam today and it went as well as it could have done, so thank you for all your help, with this and with other questions, it's greatly appreciated!
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