MadGraph5_aMC@NLO

Avoid common diagrams in pp>tt and pp>tw (+jets)

Asked by akash

Hi,

I would like to generate single and pair top production, through p p > t t~ , and p p > t w-. Since I need to generate the tW process, I have to work in the 5 flavour scheme.

Now if I want to generate these processes with additional jets, I notice that there are common diagrams. For example, at vector-boson level the following have some common diagrams:

p p > t t~, (t > w+ b), (t~ > w- b~)
p p > t w- b~, (t > w+ b)

If I generate both the processes together (via add process), I see that the issue of common diagrams still persists (if I inspect with "display diagrams").

Is there a way to generate these processes while avoiding commnon diagrams? Please advise.

Thank you.

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
Last query:
Last reply:
Revision history for this message
Best Olivier Mattelaer (olivier-mattelaer) said : 		#1

One solution is likely to use the "$ t~" syntax.

i.e.
p p > t t~, (t > w+ b), (t~ > w- b~)
p p > t w- b~, (t > w+ b) $t~

You will still have the same diagram twice but each diagram is associated to a phase-space cut
in the context of ", (t~ > w- b~)" a onshell cut is associated to the anti-top
while in the context of
p p > t w- b~, (t > w+ b) $t~, you will have an anti-onshell cut so the opposite cut.
So you would split the phase-space in two part and forbid the interference on the area which is considered as "onshell".

Now if you want to generate both together, then the best is to keep that interference term on the full phase-space and then generate only
p p > t w- b~, (t > w+ b)
but I guess this is not your point.

Cheers,

Olivier

Revision history for this message
akash (ranade1) said : 		#2

Thanks Olivier Mattelaer, that solved my question.