Understanding Quark-Gluon Interactions: Deciphering Feynman Diagrams

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NUKE1989
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Hi all. I am new here but i decided to work a bit more and finish my diploma faster so i think i will use this forum more from now on.

I was studing about quark color changes, quark interactions, gluons and generally the strong force. As i saw the Feynman diagrams i felt a bit confused.

What are the laws in order to know which gluon is emmited each time? For example in my first pic why is this a green-antiblue gluon and not a blue-antigreen?

In the second picture how do i know its 1/√6(RR+GG-2BB) and not 1/√2 (RR+BB) for example?

And in the knots again how do i found those numbers?

Thanks for your time!
 
Attachments
  • Feynman diagram: a blue quark line and a green quark line meet a wavy gluon line labeled green-antiblue gluon; outgoing lines are labeled green and blue.
    gluon.gif
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  • Feynman diagram of a B quark and antiquark pair scattering via a gluon exchange, with a gluon colour-state superposition 1/√6(RR̄ + GḠ − 2BB̄) and dashed outgoing lines labelled −2/√6 and 2/√6.
    gluon2.jpg
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The color should flow, so in the first the blue antiparticle is like an antiblue particle. And the green just flows forward.