# Gama gamma interaction

by DMESONS
Tags: gama, gamma, interaction
 P: 27 Hi guys, Could someone show me how can I evaluate/measure the cross section of gamma+gamma --> electron + positron I'll be thankful for your help 1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution
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P: 2,953
 Quote by Alhakami Hi guys, Could someone show me how can I evaluate/measure the cross section of gamma+gamma --> electron + positron I'll be thankful for your help 1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution

have you done calculations of cross sections before? Have you done, say, Moller scattering?
This is a long calculation so it's impossible to show you all the steps if you haven't done any calculations. If you have, I can help you get through steps if you are stuck. First, did you draw the Feynman diagrams?
 P: 27 Thanks nrged I have done the most of calculation. Where I got four terms of Trace {Amplitude}. As you knew in the C.M. we have a specific formula for differential cross section Diff. Cross Sect. = {1/{64* Pi^2)*(E1+E2)^2}*{|p3|/|p1|}*|M|^2 That is for interaction(in general) A+B--> C+D My question is about p1 ? Is p1=pA or p1=pB ??? or do you think A and B have the same momentum in C.M. frame"even if they have different masses"? Thanks for you help