MadGraph5_aMC@NLO

Is MLM jet matching needed for simultaneous generation of WW and W+jj processes?

Asked by HH

Dear experts,

I am generating events for the Standard Model processes

define w = w+ w-
generate e+ e- > w+ w- weighted<=99
add process e+ e- > w j j weighted<=99

I looked at the Feynman diagrams provided by MG5. It seems that decaying W bosons in the first process produces hard processes which are already generated by the matrix element. So, I concluded that I should use MLM jet matching to avoid double-counting. I wanted to make sure if I am right. Is there really double-counting and do I really need to perform jet matching for these processes?

Thanks in advance for your help.

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

Do you have double counting? YES
Do you need MLM here? No this is not a QCD double counting.

Now since I do not know what you tried to achieved it is difficult to comment more on what you try to achieve.
One interesting syntax to limit the double-counting is the "$" syntax that forbids the following particles to be on resonance peak
add process e+ e- > w j j $ w weighted<=99

Cheers,

Olivier

PS: Be sure to carefully validate your process generation since splitting a process into sub-piece is sometimes tricky due to symmetry factor. I guess that for w+ w- you should stay away of that but please check.

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HH (hh-madgrapher) said : 		#2

Thanks for your reply. So, MLM jet matching only removes QCD double counting. Is there any algorithm to remove non-QCD double countings?

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#3

You should check the litterature.

> On 15 Apr 2021, at 07:11, HH <email address hidden> wrote:
>
> Question #696502 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/696502
>
> Status: Answered => Open
>
> HH is still having a problem:
> Thanks for your reply. So, MLM jet matching only removes QCD double
> counting. Is there any algorithm to remove non-QCD double countings?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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HH (hh-madgrapher) said : 		#4

Thanks for your help.