- #1
Chrispy92
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The question is "Make a simple estimate of the order of magnitude of the ratio of the cross sections (electron,positron->2photons) and (electron,positron->3photons)"
Now I know that cross section is proportional to (1/q^4)*(Phase space factor)*(Coupling constant) where q^2 = E^2 - p^2. We are also told that the difference in phase space factors are negligible so will be canceled in the ratio.
I think I can find coupling constant as g^(number of vertices).
My question is; can you actually find the q^2 with the information I've been given? If not am I meant to assume that it's the same for both, but then the ratio would just equal g which makes no sense. Any help would be really appreciated :)
Now I know that cross section is proportional to (1/q^4)*(Phase space factor)*(Coupling constant) where q^2 = E^2 - p^2. We are also told that the difference in phase space factors are negligible so will be canceled in the ratio.
I think I can find coupling constant as g^(number of vertices).
My question is; can you actually find the q^2 with the information I've been given? If not am I meant to assume that it's the same for both, but then the ratio would just equal g which makes no sense. Any help would be really appreciated :)