MadGraph5_aMC@NLO

Want to add a model but receive an error for loop calculations.

Asked by Brian Keith Ragsdale

  I received warm and very generous help from Olivier Mattelaer while trying to perform loop calculations in MadGraph, specifically h > a a [noborn=QED] using the loop_qcd_qed_sm model; the discussion can be found here: https://answers.launchpad.net/mg5amcnlo/+question/697603.

  Now, I need to connect this to my real goal of calculating Z > Z' a. The plan of action is to import the aforementioned model in conjunction with the DMsimp_s_spin1 model to include the necessary particles for this interaction. The DMsimp_s_spin1 model can be found here under attachments, near the bottom: https://feynrules.irmp.ucl.ac.be/wiki/DMsimp#no1.

  I first imported DMsimp_s_spin1 and attempted to add loop_qcd_qed_sm. This is there error I receive:

      Command "add model loop_qcd_qed_sm" interrupted with error:
      USRMODERROR : Add-on model can not be loop model.

  For generality, I then tried importing loop_qcd_qed_sm and then adding DMsimp_s_spin1 and received:

      Command "add model DMsimp_s_spin1" interrupted with error:
      USRMODERROR : Base Model doesn't follows UFO convention

  So it seems neither direction works as one would expect. To clarify, my goal is to perform a loop calculation in the framework of a BSM model that includes light Z'.
  I'm interested in expanding on the work in this paper: https://arxiv.org/abs/2010.00021, which uses two distinct U(1) gauge symmetries (B-L and B) to produce the Z' boson. I am using the module list given in the previous discussion, but for ease of access I will list the specifics:

      Currently Loaded Modules:
        1) gcc/10.2.0 2) anaconda3/2021.05

inside the fix:

      https://bazaar.launchpad.net/~maddevelopers/mg5amcnlo/LTS_dev/revision/321

    I want to thank Olivier again and look forward to helpful discussion.

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

Merging two NLO model together is close to impossible to do in a fully consistent way. This is why none of your attempt are working.
To be honest, I have no clue on how to do that correctly. Especially here since you want to perform a loop computation which is not in the loop_qcd_qed_sm model. No way that I can compute the R2 counter-term for the new model.

The only solution is to use FeynRules and NLOCT to extend the DMsimp model to include within the UFO model the Electroweak loop.

Cheers,

Olivier

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Brian Keith Ragsdale (bransbrain) said : 		#2

I've managed to get the programs working: FeynRules, FeynArts, and NLOCT. And I've been reading arXiv articles, manuals on the matter. Do you know a good example or source to study? Everything seems to establish a context but I find it difficult to use their ideas to attack this project.

Thanks,
Brian Keith Ragsdale II

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Olivier Mattelaer (olivier-mattelaer) said : 		#3

Hi,

This is something where I do not have any experience (I do not even have a mathematica license...)
Sorry,

Olivier

> On 23 Jun 2021, at 15:50, Brian Keith Ragsdale <email address hidden> wrote:
>
> Question #697646 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/697646
>
> Status: Answered => Open
>
> Brian Keith Ragsdale is still having a problem:
> I've managed to get the programs working: FeynRules, FeynArts, and
> NLOCT. And I've been reading arXiv articles, manuals on the matter. Do
> you know a good example or source to study? Everything seems to
> establish a context but I find it difficult to use their ideas to attack
> this project.
>
> Thanks,
> Brian Keith Ragsdale II
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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Brian Keith Ragsdale (bransbrain) said : 		#4

Okay, I will update the post once I complete this step in the project so the information is publicly available.

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