Can someone explain to me what is a Feyman diagram color-suppressed at the tree-level? It's my first post, sorry if I'm too needy, I will try to improve. Thank you for the answers.
Miralansa, Welcome to PF! It always helps to start out by giving a reference. Where did you hear the term color suppression? Did they try to explain what it meant? Did they give an example? How about Googling "color suppressed" and looking up the first few hits.
This is a color-favored Feynman diagram. I think I need to do the Clebschâ€“Gordan of SU(3) for initial and final state to understand this, because they are in a given representation to be bound states. I'm not sure of this. Thank you for the reply.
I still don't understand exactly what your question is, or how much you have already researched it. Page 4 of this PDF gives a very simple explanation of what color-suppressed means. The quick answer is that the suppression factor is 3^{2}, but this turns out to be pretty far off. The long answer is that the factor depends on a more detailed modeling of QCD interactions.
I have read these: http://arxiv.org/abs/hep-ph/9504326 http://arxiv.org/abs/1104.4144 http://arxiv.org/abs/hep-ph/9404283v1 I'm searching to understand a more detailed modeling of QCD interactions. For example in exchange diagram, Rosner says that you have to consider 3 or more gluon for the singlet [itex]\phi[/itex], why? It's important because you have to consider all the diagrams in Monte-Carlo. Maybe I'm doing the wrong questions, in the wrong place. Sorry.
For posterities, a good summary of B physics, that explains ideas, without a lot of calculations is this: http://arxiv.org/abs/hep-ph/0111177 With it you can check if you have understood, without reading 3 or 4 books.