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Why we use the trace calculation? 
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#1
Mar1114, 02:36 AM

P: 22

Dear all
When we calculating the cross section of particles, we apply the trace calculation. This is not clear for me, why we use the trace calculation? Thank you all. 


#2
Mar1114, 08:48 AM

Thanks
P: 1,948

The trace averages over many possible initial states. Useful when the initial state is not known or the beam of particles contains a mixture of states.



#3
Mar1114, 08:56 AM

Thanks
P: 1,948

Also, if you're talking about intermediary (virtual) particles than taking the trace ensures that all possible intermediary states are taken into account.



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