MadGraph5_aMC@NLO

Higgs_Effective_Couplings h( -> \gamma \gamma)tt~

Asked by SOUAD SEMLALI

Dear Olivier,

I am trying to generate events for the following process: tth, with $h -> \gamma \gamma$ using the Higgs effective couplings UFO file. However, the cross-section is very small. For a sanity check, I just run the gg > h t t~, without decaying either top or Higgs, using both the SM and the Higgs effective couplings.

generate g g > h t t~, sigma = 0.285 ± 0.0033 pb (using SM),
generate g g > h t t~, sigma = 0.0003412 ± 4.3e-06 pb (with Higgs effective couplings UFO).

Note that I didn't enforce any generation-level cuts in both cases. I am a bit puzzled because of the large discrepancy. The small cross-section, while using Higgs-effective couplings UFO file, leads to a very negligible cross-section of gg -> tt~h(-> \gamma \gamma), which is not the true case.

Many thanks for any help in solving this issue.

Best

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

Hi,

Which model are you using exactly?
Are you using HC_NLO_X0_UFO-heft?

In that model restriction, they have set the yukawa of the top to zero.
And therefore for your process you do not have the Higgs emission from the top line.
Did you check the documentation of the model on why they have done that?
If this is not explained in the documentation my suggestion would be to contact the author of the model.

Cheers,

Olivier

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SOUAD SEMLALI (souad-sem) said : 		#2

Dear Olivier,

Thank you for your prompt answer. I am using the following UFO file:

Higgs_Effective_Couplings_UFO from https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/Models/HiggsEffective. I don't think the Yukawa coupling is set to zero in such a case. Am I missing something?

###################################
## INFORMATION FOR YUKAWA
###################################
BLOCK YUKAWA #
      4 1.270000e+00 # ymc
      5 4.200000e+00 # ymb
      6 1.645000e+02 # ymt
      13 1.056600e-01 # ymm
      15 1.777000e+00 # ymtau

Many thanks for your help.

Best,

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Olivier Mattelaer (olivier-mattelaer) said : 		#3

I did run the following
import model Higgs_Effective_Couplings_UFO (after removing the model to ensure that the latest version was used)
generate g g > t t~ h
output
launch -f

and the result was:

  === Results Summary for run: run_01 tag: tag_1 ===

     Cross-section : 0.3635 +- 0.001093 pb
     Nb of events : 10000

I also check for "g g > h t t~" and got the same result.

Finally I did run the check command on that process and nothing bad was reported:

INFO: Note That all width have been set to zero for those checks

Lorentz invariance results:
Process Min element Max element Relative diff. Result
g g > t t~ h 2.0346647064e-06 2.0346647064e-06 3.3304079816e-15 Passed
Summary: 1/1 passed, 0/1 failed
Gauge results:
Process matrix BRS ratio Result
g g > t t~ h 8.7102248080e-07 2.2283081999e-36 2.5582671504e-30 Passed
Summary: 1/1 passed, 0/1 failed
Gauge results (switching between Unitary/Feynman/axial gauge):
Process Unitary Feynman Relative diff. Result
g g > t t~ h 4.7571060621e-07 4.7571060621e-07 0.0000000000e+00 Passed
Summary: 1/1 passed, 0/1 failed
Process permutation results:
Process Min element Max element Relative diff. Result
g g > t t~ h 2.5491339269e-06 2.5491339269e-06 3.3228263855e-16 Passed
Summary: 1/1 passed, 0/1 failed

So are you sure about your result? Which version are you using?

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SOUAD SEMLALI (souad-sem) said : 		#4

Dear Olivier,

Thank you for your help. I am getting now similar results. The problem is
due to using a version that was old and not updated.

Many thanks.

Best,

Le ven. 15 mars 2024 à 13:01, Olivier Mattelaer <
<email address hidden>> a écrit :

> Your question #709583 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/709583
>
> Olivier Mattelaer posted a new comment:
> I did run the following
> import model Higgs_Effective_Couplings_UFO (after removing the model to
> ensure that the latest version was used)
> generate g g > t t~ h
> output
> launch -f
>
> and the result was:
>
> === Results Summary for run: run_01 tag: tag_1 ===
>
> Cross-section : 0.3635 +- 0.001093 pb
> Nb of events : 10000
>
> I also check for "g g > h t t~" and got the same result.
>
> Finally I did run the check command on that process and nothing bad was
> reported:
>
> INFO: Note That all width have been set to zero for those checks
>
> Lorentz invariance results:
> Process Min element Max element Relative diff.
> Result
> g g > t t~ h 2.0346647064e-06 2.0346647064e-06 3.3304079816e-15
> Passed
> Summary: 1/1 passed, 0/1 failed
> Gauge results:
> Process matrix BRS ratio
> Result
> g g > t t~ h 8.7102248080e-07 2.2283081999e-36 2.5582671504e-30
> Passed
> Summary: 1/1 passed, 0/1 failed
> Gauge results (switching between Unitary/Feynman/axial gauge):
> Process Unitary Feynman Relative diff.
> Result
> g g > t t~ h 4.7571060621e-07 4.7571060621e-07 0.0000000000e+00
> Passed
> Summary: 1/1 passed, 0/1 failed
> Process permutation results:
> Process Min element Max element Relative diff.
> Result
> g g > t t~ h 2.5491339269e-06 2.5491339269e-06 3.3228263855e-16
> Passed
> Summary: 1/1 passed, 0/1 failed
>
> So are you sure about your result? Which version are you using?
>
> --
> You received this question notification because you asked the question.
>

--
Souad SEMLALI

Revision history for this message
SOUAD SEMLALI (souad-sem) said : 		#5

Thanks Olivier Mattelaer, that solved my question.