Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Another question on rates, propagators, etc

  1. May 31, 2008 #1
    Please take a look at the file "Feynman.pdf". The ratio rate for the two decays is shown in the second file, "rate.pdf".

    I understand it takes that form because the usW vertex is Carribbo supressed relative to the udW vertex. My concern is that the ratio is only squared.

    Rate is proportional to the amplitude *squared*. And the amplitude is proportional to the square of the coupling constant (multiplied by the propagator). So the transition rate must be proportional to the fourth power of the coupling constant, right?

    Is the expression in rate.pdf wrong?
     

    Attached Files:

  2. jcsd
  3. May 31, 2008 #2

    pam

    User Avatar

    The W-mu-nu coupling is the same for each so the amplitude is proportional to the first power of each g.
    However, I would also expect a strong dependence on the mass ratio k/pi because the muon
    has to have positive helicity for this decay.
     
  4. May 31, 2008 #3

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2015 Award

    Additionally, the ratio can't be right because it completely ignores the W propagator: there's 10 times as much Q in the kaon decay.
     
  5. Jun 2, 2008 #4
    Thanks for your replies pam and Vanadium.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Another question on rates, propagators, etc
  1. Another nuke question (Replies: 8)

Loading...