MadGraph5_aMC@NLO

how to define Mandelstam variables in UFO format

Asked by Arka Santra

Hello,
 I want to write a UFO model where I need to use Mandelstam variables s, t and u. From Table 6 of this reference http://arXiv.org/abs/arXiv:1108.2040
I see that the momentum of the particle is defined as P(1,N) (momentum of the Nth particle).

If I have a two-particle collision, how do I define the variable s inside the UFO model? Should it be:

s = ( (P(1,1)+P(1,2))*(P(1,1)+P(1,2)) )
?

Thank you,
Arka

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

Variable in UFO are local to the vertex, therefore I do not see how you can define in the UFO format such type of variable (but eventually for 4-point vertices and still it will break some UFO convention)
You can obviously ask the opinion of other UFO author and/or FeynRules author if they see a way for that.

Cheers,

Olivier

> On Nov 1, 2017, at 18:23, Arka Santra <email address hidden> wrote:
>
> New question #660235 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/660235
>
> Hello,
> I want to write a UFO model where I need to use Mandelstam variables s, t and u. From Table 6 of this reference http://arXiv.org/abs/arXiv:1108.2040
> I see that the momentum of the particle is defined as P(1,N) (momentum of the Nth particle).
>
> If I have a two-particle collision, how do I define the variable s inside the UFO model? Should it be:
>
> s = ( (P(1,1)+P(1,2))*(P(1,1)+P(1,2)) )
> ?
>
> Thank you,
> Arka
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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