MadGraph5_aMC@NLO

generate gamma H samples

Asked by Winston

Dear experts, can you tell me how to generate γH samples under EFT theory by Madgraph?
1). p p > a h, including all processes.
2). p p > a > a h
3). p p > z > a h.
Here "a" denote photon. Thank you, sir.

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

You need to start to load your model within MG5aMC.

The easiest to know which model you want is to look at the FeynRules model.
When you have the name of the model, you just need to do within MG5aMC
import model NAME_OF_YOUR_MODEL

Note that your syntax 2/3 breaks gauge invariance and therefore result will not be physical (since they depend of an arbitrary choice)

Cheers,

Olivier

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Winston (adampan) said : 		#2

Thank you Sir.
Can you explain why process(2) and (3)violate gaugae invariance.
Look forword your reply.

Best regards.
Winston

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Olivier Mattelaer (olivier-mattelaer) said : 		#3

Hi,

This is because they are off-shell and therefore interferes.
For more details, please take a look at Peskin book (or the book of your choice)

What people are typically doing is the following
generate p p > z, z > h a
which correspond to the onshell z contribution
and
generate p p > h a $z
which is the syntax to forbid the z to be onshell (but keep him offshell)

Cheers,

Olivier

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Winston (adampan) said : 		#4

Dear Olivier,
I am a user of Madgraph. Would you mind I ask you a question about models in Madgrah?
what's the distinguish between models sm, sm_v4, loop_sm and loop_qcd_qed_sm? Look forword your reply.

Best regards,
Renqi Pan

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Winston (adampan) said : 		#5

Thanks Olivier Mattelaer, that solved my question.