FeynRules SM and MG5 SM lead to different results

Asked by Duarte Azevedo on 2018-02-08

Hello all,

I'm doing some model testing using FeynRules to generate the UFO file for MG5. I was getting some strange results with my new model when setting the pertinent parameters to the limit that would give me the SM back. The strange results are different cross sections for a certain process. So I've decided to create the SM UFO to compare with the SM model that comes with MG5, using the following process:

p p > z h a , h > b b~ , z > l+ l- for sqrt(s)=14TeV

And I get the following results:

with FeynRules SM [massless u,d,s,c and full-CKM] - > xs = 3.063e-4 pb

with "sm" model (default from MG5) -> xs = 1.981e-4 pb

My parameters and run_card variables are the same for both processes. So what is it that I'm missing?

Thanks,

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Last query:
2018-02-09
Last reply:
2018-02-09

This question was reopened

Hi,

Can you send me the UFO model that you get from FR? (I do not have any mathematica license)

Our internal model is actually coming from FR as well (probably an old version)
with just
1) some restriction at FR level (like the mass of the quark)
2) some restriction/change of benchmark at our level via the restrict_default.dat (like to put CKM diagonal)
This second step can by bypass/modify via import model sm-full or sm-XXX (to use instead restrict_XXX.dat)

Since the difference that seems to flash from what you say is the CKM,
I try to compute p p > z h a
both within sm and sm-ckm and both are spot on at 0.00323 pb
So this does not explain the difference. I also tried with sm-full and the same occurs.

Are you sure that both benchmark (i.e. param_card) are 100% identical?

Cheers,

Olivier

> On 8 Feb 2018, at 11:43, Duarte Azevedo <email address hidden> wrote:
>
> New question #664195 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/664195
>
> Hello all,
>
> I'm doing some model testing using FeynRules to generate the UFO file for MG5. I was getting some strange results with my new model when setting the pertinent parameters to the limit that would give me the SM back. The strange results are different cross sections for a certain process. So I've decided to create the SM UFO to compare with the SM model that comes with MG5, using the following process:
>
> p p > z h a , h > b b~ , z > l+ l- for sqrt(s)=14TeV
>
> And I get the following results:
>
> with FeynRules SM [massless u,d,s,c and full-CKM] - > xs = 3.063e-4 pb
>
> with "sm" model (default from MG5) -> xs = 1.981e-4 pb
>
> My parameters and run_card variables are the same for both processes. So what is it that I'm missing?
>
> Thanks,
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Duarte Azevedo (yuhuanknot) said : #2

Hello Olivier,

here it goes: https://drive.google.com/file/d/1U1oLb92XbJnHq2vz_2d-gaHJQWhv3h3k/view?usp=sharing

Yeah I tried both sm and sm-full. And with sm-full I get: xs ~ 1.5e-4pb

Now I've also run just the process "p p > h z a" and indeed I get something "more" similar between "my SM model" (xs ~ 3.6e-3 pb) and on sm model (xs~3.5e-3pb). So I believe the problem should be with the decays?

I'm also sending the generated param_card.dat inside the previous file. My bad, actually not sure that they are identical, since they have a different structure. So maybe the problem comes from that?

Best,
Duarte

The difference is due to the width of the Higgs which is not the same in both model.

Cheers,

Olivier

> On 9 Feb 2018, at 11:08, Duarte Azevedo <email address hidden> wrote:
>
> Question #664195 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/664195
>
> Status: Solved => Open
>
> Duarte Azevedo is still having a problem:
> Oh, I just wanted to send the message and accidentally clicked on "this
> solved my question" :p
>
> Can you please unsolve it? :)
>
> Best,
> Duarte
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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