Another question on rates, propagators, etc

  • Thread starter vertices
  • Start date
  • #1
62
0
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?
 

Attachments

  • Feynman.pdf
    58.4 KB · Views: 143
  • Rate.pdf
    58.4 KB · Views: 111

Answers and Replies

  • #2
pam
455
1
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.
 
  • #3
Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
26,722
10,287
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.
 
  • #4
62
0
Thanks for your replies pam and Vanadium.
 

Related Threads on Another question on rates, propagators, etc

  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
8
Views
710
Replies
4
Views
2K
Replies
5
Views
1K
Replies
3
Views
2K
  • Last Post
Replies
8
Views
2K
Replies
87
Views
9K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
4
Views
4K
  • Last Post
Replies
4
Views
4K
Top