NCG in MadGraph, is it possible?

Asked by spaktinat on 2018-06-11

Dear MadGraph Experts,
I am trying to implement a part of the Non Commutative Geometry (NCG) lagrangian in FeynRules and extract the UFO files to be used in MG for event generation. The FeynRules package and the UFO interface work with no error, but the model does not work in MG, complaining about the Lorentz indices,
"LorentzObjectRepresentationError : Invalid addition. Object doen't have the same lorentz indices : [-1, 3] != [-3, -2]"

Since NCG can violate the lorentz invariance, I was wondering if MG can support such a model? If it can not, I am wasting my time to do an impossible mission.
Any hint from your side is highly appreciated.
Thanks,
Saeid

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Last query:
2018-06-11
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2018-06-11

Hi,

> "LorentzObjectRepresentationError : Invalid addition. Object doen't have the same lorentz indices : [-1, 3] != [-3, -2]"

This means that one of your lorentz structure is of the type
P^\mu + P^\nu
(i.e. a sum where the uncontracted indices are not the same)

> Since NCG can violate the lorentz invariance, I was wondering if MG can support such a model? If it can not, I am wasting my time to do an impossible mission.
> Any hint from your side is highly appreciated.

This is obviously outside of our confort zone.

Few issue that i can think of:
1) Your lorentz structure should not be of the form above
2) We assume the CPT theorem (and therefore particles and anti-particles have the same width)
3) If you want to use the phase-space integration, we always generate the events in the CMS frame. (and evaluate the matrix-element in that frame) then before writting the events, we boost it in the frame defined in the configuration file.

It is possible that other issue can be present but like that I only see the above ones.

Cheers,

Olivier

> On 11 Jun 2018, at 12:53, spaktinat <email address hidden> wrote:
>
> New question #670124 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/670124
>
> Dear MadGraph Experts,
> I am trying to implement a part of the Non Commutative Geometry (NCG) lagrangian in FeynRules and extract the UFO files to be used in MG for event generation. The FeynRules package and the UFO interface work with no error, but the model does not work in MG, complaining about the Lorentz indices,
> "LorentzObjectRepresentationError : Invalid addition. Object doen't have the same lorentz indices : [-1, 3] != [-3, -2]"
>
> Since NCG can violate the lorentz invariance, I was wondering if MG can support such a model? If it can not, I am wasting my time to do an impossible mission.
> Any hint from your side is highly appreciated.
> Thanks,
> Saeid
>
> --
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