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Electro weak vertices 
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#1
Mar2912, 03:02 PM

P: 10

I have a question about Feynman Diagrams:
let's say we have a process: up antidown > W+ > up antidown... the first vertex is like V_CKM G PL ( mixing, gamma, projector) the second is the same..only with the complex conjugate CKM matrix... but why?... If I compute the M* I have to bar the vertices..and there I got the same vertex..with the same flow..but there I would change PL to PR and interchange PL and Gamma..why is that the case? 


#2
Mar3012, 03:19 AM

P: 62

Best, Francesco 


#3
Mar3012, 07:03 AM

P: 136

I think another way of looking at it is like this.
That Feynman diagram also describes the processes u → W^{+} + das all I have done here is replace the incoming antid with an outgoing d, and the outgoing antid with an incoming d. The CKM matrix, as defined, is the factor for 'converting' downtype quarks to uptype, eg u> = V_{ud} d>Provided only the three known generations of quarks exist, the CKM matrix must be unitary, and hence V^{1} = V^{†}so d> = V^{*}_{ud} u> 


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