# Some basic questions on Madspin with EFT model

Asked by David Seith on 2020-02-07

This is mostly some (simple) beginner question on Madspin.
I want to generate single top t-channel events with an EFT model. The production should be generated with Madgraph and the decay should be generated with Madspin.

Then in the proc card I do:

import model dim6top_LO_UFO
generate p p > t j \$ w+ w- DIM6=1

decay t > w+ b DIM6=1, w+ > ell+ vl

Will setting the DIM6=1 in the madspin card ensure that Madspin uses the EFT model for the decay?

What happens if I do DIM6^2==1 or DIM6^2==2 in the proc card, will this be true for both production and decay? Or only count for the production? (I already noticed it is not possible to use this syntax in the madspin card)

If I use a reweight card in which I set different coupling points, will all of them be taken into account by Madspin? Or will it use only the default?

Can I find the cross section including the full decay as calculated by Madspin somewhere? Because in the output it only shows the cross sections from Madgraph.

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2020-02-07
 Olivier Mattelaer (olivier-mattelaer) said on 2020-02-07: #1

Hi,

> Will setting the DIM6=1 in the madspin card ensure that Madspin uses the EFT model for the decay?

I guess that you have noticed the warning when you use the syntax
> DIM6=1
whcih tells that
DIM6=1 is interpreted as DIM6<=1
The same is True for the Decay so your syntax is using the EFT model yes.
But you might be dominated by the SM decay.

> What happens if I do DIM6^2==1 or DIM6^2==2 in the proc card, will this be true for both production and decay?

MadSpin will crash if you try to use MadSpin with such syntax in the production.

> If I use a reweight card in which I set different coupling points, will all of them be taken into account by Madspin? Or will it use only the default?

By default reweighting is called before MadSpin.
So in that case MS is based on the central-weight and all weight are just rescaled by the BR ratio.

If your benchmark impacts the shape or BR, then it is better to run first MadSpin
and then run the re-weighting on the decay sample.
(This being said re-weighting performs badly if the width is impacted due to the impact of the BW modification).

> Can I find the cross section including the full decay as calculated by Madspin somewhere? Because in the output it only shows the cross sections from Madgraph.

This is just production times BR so this is trivial in principle.
But you have those value in the html page obviously
and you can also access them via the print_result command

Cheers,

Olivier

> On 7 Feb 2020, at 20:03, David Seith <email address hidden> wrote:
>
> New question #688589 on MadGraph5_aMC@NLO:
>
> This is mostly some (simple) beginner question on Madspin.
> I want to generate single top t-channel events with an EFT model. The production should be generated with Madgraph and the decay should be generated with Madspin.
>
> Then in the proc card I do:
>
> import model dim6top_LO_UFO
> generate p p > t j \$ w+ w- DIM6=1
>
> and in the madspin card:
>
> decay t > w+ b DIM6=1, w+ > ell+ vl
>
> Will setting the DIM6=1 in the madspin card ensure that Madspin uses the EFT model for the decay?
>
> What happens if I do DIM6^2==1 or DIM6^2==2 in the proc card, will this be true for both production and decay? Or only count for the production? (I already noticed it is not possible to use this syntax in the madspin card)
>
> If I use a reweight card in which I set different coupling points, will all of them be taken into account by Madspin? Or will it use only the default?
>
> Can I find the cross section including the full decay as calculated by Madspin somewhere? Because in the output it only shows the cross sections from Madgraph.
>
>
> --