ALOHA output matrix element to Fortran

Asked by Laurent Vashmo on 2018-06-12

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!

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
2018-06-13
Last query:
2018-06-13
Last reply:
2018-06-12

This question was reopened

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.

Laurent Vashmo (laurentvashmo) 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!

Laurent Vashmo (laurentvashmo) 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?

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.

Laurent Vashmo (laurentvashmo) said : #6

Ok, perfect, thank you very much!

Laurent Vashmo (laurentvashmo) said : #7

Thanks Olivier Mattelaer, that solved my question.