# A Way of Grouping Feynman Diagrams

Dear MadGraph authors

I have a question on how MadGraph utilizes a coupling order information when it classifies Feynman diagrams.

I tried to dig out all the relevant information here, and found this:

- MadGraph decomposes the Feynman diagrams based on independent phase-space integrations to speed up its computations (https:/

- It rather looks at the structures of matrix elements (or squared amplitudes), and see whether there is any peak structure, for example, in their integrands. Then it classifies diagrams according to the integration structures.

- As a result, even if two Feynman diagrams have a same coupling order, if their structures of amplitudes are different, e.g s-channel and t-channel, then they are classified differently. The method is called Single-

- Another consequence is that if one uses a four-flavor scheme, diagrams with b-quark are classified differently from other light quarks because they contain mb in their amplitudes, hence classified separately.).

Given above, Is there any pre-step (before even classifying the structure of integration) that utilizes the information of coupling-order (e.g. QCD = 2, QED = 0)? I guess this is too much detail, but I'm wondering if there is any role of coupling order when MadGraph classifies the diagrams.

Thanks!

Best regards,

Han

## Question information

- Language:
- English Edit question

- Status:
- Solved

- Assignee:
- No assignee Edit question

- Solved by:
- Olivier Mattelaer

- Solved:

- Last query:

- Last reply: