MadGraph5_aMC@NLO

ALOHA output matrix element to Fortran

Asked by Laura M

Hi,

I would like to obtain the matrix element for a given process to be able to use it in a Fortran code made on my own. To generate the process I do, for example:

>> generate u u~ > t t~
>> output standalone uux_ttx_sa

but from the files I get, I am not so sure how, from another .f file can I obtain the matrix element and do whatever I want with it. I read some stuff about ALOHA, but I am not so sure how to use it and how could I get the matrix element from there. I would appreciate if someone could shed a bit of light on that, or refer me to somewhere where I can find the information. Up to now, I could not solve it.

Thank you in advanced!

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Olivier Mattelaer
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Best Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

ALOHA output the helicity amplitude routine which are the building block for MadGraph to build the Feynman diagram. ALOHA is not able to output matrix element directly. (There is a dream project to update ALOHA to allow him to do it for simple 2 to 2 process to speed-up such type of computation of the matrix-element)

So what you need is really the standalone output.
You can now go to the directory

>>> uux_ttx_sa/SubProcesses/P0_uux_ttx
type make check
./check
the file check_sa.f
is is a simple driver file that you can replace by your executable and which gives you an example on how to interface your code.

Cheers,

Olivier

> On 12 Jun 2018, at 15:47, Laurent Vamo <email address hidden> wrote:
>
> New question #670161 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/670161
>
> Hi,
>
> I would like to obtain the matrix element for a given process to be able to use it in a Fortran code made on my own. To generate the process I do, for example:
>
>>> generate u u~ > t t~
>>> output standalone uux_ttx_sa
>
> but from the files I get, I am not so sure how, from another .f file can I obtain the matrix element and do whatever I want with it. I read some stuff about ALOHA, but I am not so sure how to use it and how could I get the matrix element from there. I would appreciate if someone could shed a bit of light on that, or refer me to somewhere where I can find the information. Up to now, I could not solve it.
>
> Thank you in advanced!
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Laura M (laumova) said : 		#2

Thank you Oliver, I think that kind of solved my problem, but my question now is if I can 'get' this matrix element as it does check_sa.f if I am in a complete different folder, that is not even in Madgraph folder.
Thank you!

Revision history for this message
Laura M (laumova) said : 		#4

So, the thing I mean, is that the chck_sa.f is in fact a link to another file, so how can I do the same as this file outside this folder? Is it possible?

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#5

Yes sure having those in different directory is not an issue.
(only the linker will check that all function are defined0

Cheers,

Olivier

> On 12 Jun 2018, at 16:13, Laurent Vashmo <email address hidden> wrote:
>
> Question #670161 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/670161
>
> Status: Solved => Open
>
> Laurent Vashmo is still having a problem:
> So, the thing I mean, is that the chck_sa.f is in fact a link to another
> file, so how can I do the same as this file outside this folder? Is it
> possible?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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Laura M (laumova) said : 		#6

Ok, perfect, thank you very much!

Revision history for this message
Laura M (laumova) said : 		#7

Thanks Olivier Mattelaer, that solved my question.