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Difference between coupling constant and strength parameter

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Aug25-14, 09:20 AM
P: 22
Hello to everyone,

I got a little bit confused between the coupling constant [itex]g_W[/itex] and the strength parameter [itex]\alpha_W[/itex] in the weak interaction. For what I know they should both give an idea of the strength of the interaction but I miss to understand what's the difference between them.
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Aug25-14, 10:24 AM
P: 1,030
If I understand your quantities well...alpha is called the (running) coupling constant too.
There is no difference between the one or the other...
[itex] \alpha_{W}= \frac{g_{W}^{2}}{4 \pi}[/itex]

The one appears on the Lagrangian as the coupling strength between the fields on vertices.
The other appears in the Feynman diagrams of interactions when you have two vertices.
Aug25-14, 01:59 PM
P: 22
Thank you for the answer!

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