Setting QED and QCD coupling orders in mg5
Hello,
I would like to ask a clarification on how someone can specify the QED/QCD order in the production.
My understanding is that if nothing is specified, the lowest QED order is considered.
Now I am trying to isolate some high order QED diagrams like the famous
W+W+ EWK production therefore I though about writing something like:
generate p p > e+ mu+ vl vl j j QED=6
(I know that this process alone is not gauge invariant but I assume that this will not be a big problem with the generator).
When looking at the list of diagrams I (surprisingly) see some diagrams with order:
QCD=2, QED=4 ....
Is this expected?
Obviously those diagrams go away if I also requires QCD=0.
The problem with that is that obviously I cannot then use the NLO calculation ([QCD])
since I get the message:
WARNING: Some loop diagrams contributing to this process are discarded because they are not pure (QCD)-perturbation.
Make sure you did not want to include them.
... and obviously the real emission diagrams are not there.
thanks a lot,
Valerio
Question information
- Language:
- English Edit question
- Status:
- Answered
- Assignee:
- marco zaro Edit question
- Last query:
- Last reply:
Can you help with this problem?
Provide an answer of your own, or ask Valerio Dao for more information if necessary.