Zero cross section in Madgraph Version 2.4.2

Asked by Andrea Delgado on 2019-09-18

Hello all,

Thank you for your help in advance.

I am trying to run Madgraph importing a model for a Z' with 4 coupling parameters.

I do:
import model zprime_UFO
define p = p b b~
define j = j b b~
generate p p > zp, zp > j j@0
add process p p > zp j, zp > j j@1
add process p p > zp j j, zp > j j@2
output zprime_dbs1test

I am trying to run Madgraph 2.4.2 because this is the required version for 2016 CMS analyses, however, whenever I set one of my parameters to 1.0 I get a 0 cross section. If I run the exact same setup on the latest version you can download from the website, I get a cross section !=0, which is what I expect from the model.

Do you have any insight as to what might have changed between releases that can cause this difference? Or how can I tweak version 2.4.2 to work with this model and phase space?

Thanks again

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
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Last query:
2019-09-18
Last reply:
2019-09-20

Hi,

Like this I do not remember any change that are trivially related to such effect.
Now they are so many stuff that change the last 3 years that it is difficult to remember all the issue that I have fixed (in top of knowing if the fix where discover in a development code or in a released code). In top of that CMS never use an official version of the code but apply a bunch of patch (so your version is likely closer to 2.5.0 than it is of 2.4.2) which make this impossible to debug on our side.

Finally what kind of "tweak" do you expect? if you want a patch, I can create you a patch to move from 2.4.2 to 2.6.6 that will solve your issue. But I guess that you are not allowed to use patch.

Cheers,

Olivier

> On 19 Sep 2019, at 01:08, Andrea Delgado <email address hidden> wrote:
>
> New question #684024 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/684024
>
> Hello all,
>
> Thank you for your help in advance.
>
> I am trying to run Madgraph importing a model for a Z' with 4 coupling parameters.
>
> I do:
> import model zprime_UFO
> define p = p b b~
> define j = j b b~
> generate p p > zp, zp > j j@0
> add process p p > zp j, zp > j j@1
> add process p p > zp j j, zp > j j@2
> output zprime_dbs1test
>
> I am trying to run Madgraph 2.4.2 because this is the required version for 2016 CMS analyses, however, whenever I set one of my parameters to 1.0 I get a 0 cross section. If I run the exact same setup on the latest version you can download from the website, I get a cross section !=0, which is what I expect from the model.
>
> Do you have any insight as to what might have changed between releases that can cause this difference? Or how can I tweak version 2.4.2 to work with this model and phase space?
>
> Thanks again
>
>
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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