Interference in processes with decays

Asked by teddym on 2019-08-16

Hello:
     We want to simulate a process in a model with two newly defined coupling order C1 and C2. In this process, the diagram involves either one C1 coupling or one C2 couplings. We want to generate C1^2, C2^2 and C1*C2 order events separately such that we can study the interference effect in detail. However, there will be a W/Z in the final state which will decay.

    However, we see that we can't use syntax like: generate xx xx > xx xx z w C1^2==1 C2^2==1, w > l vl, z > l- l+, which will return the error saying we can't specify square coupling order with decay. (This error also prevent us using MadSpin with full spin correlation )

   Further, we also don't want to use MadSpin without spin correlation (spinmode = none), as the spin correlation may affect the final lepton momentum which will be used to construct some observable to study the interference effect.

  We found that in this FAQ https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/FAQ-General-15, you mention a way to select diagram. This can help to selection C1^2==2 and C2^2==2 case. However, it seems that I can not use it to select only interference.

Do you know any possible method to do that? Thanks!

Best
Ted

Question information

Language:
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MadGraph5_aMC@NLO Edit question
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Last query:
2019-08-16
Last reply:
2019-08-16

No I do not

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________________________________
From: <email address hidden> <email address hidden> on behalf of teddym <email address hidden>
Sent: Friday, August 16, 2019 5:42:53 AM
To: Olivier Mattelaer <email address hidden>
Subject: [Question #682924]: Interference in processes with decays

New question #682924 on MadGraph5_aMC@NLO:
https://answers.launchpad.net/mg5amcnlo/+question/682924

Hello:
     We want to simulate a process in a model with two newly defined coupling order C1 and C2. In this process, the diagram involves either one C1 coupling or one C2 couplings. We want to generate C1^2, C2^2 and C1*C2 order events separately such that we can study the interference effect in detail. However, there will be a W/Z in the final state which will decay.

    However, we see that we can't use syntax like: generate xx xx > xx xx z w C1^2==1 C2^2==1, w > l vl, z > l- l+, which will return the error saying we can't specify square coupling order with decay. (This error also prevent us using MadSpin with full spin correlation )

   Further, we also don't want to use MadSpin without spin correlation (spinmode = none), as the spin correlation may affect the final lepton momentum which will be used to construct some observable to study the interference effect.

  We found that in this FAQ https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/FAQ-General-15, you mention a way to select diagram. This can help to selection C1^2==2 and C2^2==2 case. However, it seems that I can not use it to select only interference.

Do you know any possible method to do that? Thanks!

Best
Ted

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