Does reweighting sum over colour configurations?

Asked by Johann Brehmer on 2019-07-05

Hi Olivier et al.,

Quick question about MadGraph's reweighting feature:

I understand how it handles helicities: depending on whether set helicity False was called, it uses the helicities in the LHE file or sums over all helicities.

How are colour charges handled? Are they fixed to the colour flow in the LHE file, or is a sum over colour configurations performed? Is there a switch between both options, like there is for helicities?

Thanks a lot!
Johann

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MadGraph5_aMC@NLO Edit question
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Solved by:
Olivier Mattelaer
Solved:
2019-07-12
Last query:
2019-07-12
Last reply:
2019-07-05

Only the sum is possible. This is a serious limitation of the method. The reason is that the colour assignment is a quite complex operation and you lack knowledge in order to do it correctly.

I have just now an idea of how to do it. But I will have to do the math (and if it works it is likely need a lot of stat to make it stable)

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________________________________
From: <email address hidden> <email address hidden> on behalf of Johann Brehmer <email address hidden>
Sent: Friday, July 5, 2019 7:32:34 PM
To: Olivier Mattelaer
Subject: [Question #681816]: Does reweighting sum over colour configurations?

New question #681816 on MadGraph5_aMC@NLO:
https://answers.launchpad.net/mg5amcnlo/+question/681816

Hi Olivier et al.,

Quick question about MadGraph's reweighting feature:

I understand how it handles helicities: depending on whether set helicity False was called, it uses the helicities in the LHE file or sums over all helicities.

How are colour charges handled? Are they fixed to the colour flow in the LHE file, or is a sum over colour configurations performed? Is there a switch between both options, like there is for helicities?

Thanks a lot!
Johann

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Johann Brehmer (johannbrehmer) said : #2

Thanks Olivier Mattelaer, that solved my question.