MadGraph5_aMC@NLO

generate mu+ mu- > z, z > l+ l-

Asked by Rouzbeh

Hi,

I am trying to generate mu+ mu- > z, z > l+ l-. I imported the sm-lepton_masses model and set pdf to 0 with a muon delphes card at 3 or 10 TeV center of mass energy, but I got zero results with the following error:

1) A massive s-channel particle has a width set to zero.
 2) The pdf are zero for at least one of the initial state particles.
 3) The cuts are too strong.
  Please check/correct your param_card and/or your run_card.

However, when I tried to generate mu+ mu- > x x z, z > l+ l-, where the x is DM particles in my own UFO model the cross-section produced and I got the result. So, how can I generate the SM part (mu+ mu- > z, z > l+ l-)?

Thank you,
Rouzbeh

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Olivier Mattelaer
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Olivier Mattelaer (olivier-mattelaer) said : 		#1

The syntax with the comma is for onshell particles and is therefore associated to an onshell cut.
If you do it for
mu+ mu- > z, z > l+ l-
with PDF, this will automatically only select the onshell contribution (since you ask for it)
But without PDF, you ask such contribution is just impossible and the computation return (as it should) zero.

Cheers,

Olivier

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Rouzbeh (rouzbehi) said : 		#2

Thanks for your insightful comments. I tried this process with PDF, and I set +/-4 for the anti/muon beam. I also used eva and iww, but I still got the same zero result. I used MadGraph v3.4.2.

Best,

Rouzbeh

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Best Olivier Mattelaer (olivier-mattelaer) said : 		#3

Do you really want an onshell Z?
I guess not,
I would do
generate m+ mu- > l+ l-

In your case (you can not select the Z alone when he is offshell since the intereference with the photon is important)

Cheers,

Olivier

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Rouzbeh (rouzbehi) said (last edit ): 		#4

Thanks again for your comment.

Thanks,
Rouzbeh

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Rouzbeh (rouzbehi) said : 		#5

Thanks Olivier Mattelaer, that solved my question.

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Olivier Mattelaer (olivier-mattelaer) said : 		#6

Maybe you are looking for
mu+ mu- > vm vm~ Z , z > l+ l-

Cheers,

Olivier