Problem in defining form factors

Asked by Sayan Dasgupta on 2020-10-28

Hello,

I am trying to define a new form factor. I have created a file formfactors.py and written down my form factor with the name AAA. I have defined the new lorentz structure as

FF1 = Lorentz(name = 'FF1',
               spins = [ 3, 3, 1 ],
               structure = 'AAA*Metric(1,2)',
               formfactors=[ForFac.AAA])

The following lines are there in the top of the lorentz.py file

try:
   import formfactors as ForFac
except ImportError:
   pass

I have modified the vertex as

V_79 = Vertex(name = 'V_79',
              particles = [ P.Z, P.Z, P.H ],
              color = [ '1' ],
              lorentz = [ L.FF1 ],
              couplings = {(0,0):C.GC_59})

After importing the model and generating a process, when I try to take the output, the following error is displayed

AttributeError : 'ALOHAExpressionParser' object has no attribute 'f'

Help regarding this will be highly appreciated.

Thanks in advance.

Regards,
Sayan.

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Sayan Dasgupta
Solved:
2020-10-28
Last query:
2020-10-28
Last reply:
2020-10-28

This question was reopened

That should be an error related to your definition of the form factor.

Cheers,

Olivier

> On 28 Oct 2020, at 08:11, Sayan Dasgupta <email address hidden> wrote:
>
> New question #693684 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/693684
>
> Hello,
>
> I am trying to define a new form factor. I have created a file formfactors.py and written down my form factor with the name AAA. I have defined the new lorentz structure as
>
> FF1 = Lorentz(name = 'FF1',
> spins = [ 3, 3, 1 ],
> structure = 'AAA*Metric(1,2)',
> formfactors=[ForFac.AAA])
>
> The following lines are there in the top of the lorentz.py file
>
> try:
> import formfactors as ForFac
> except ImportError:
> pass
>
> I have modified the vertex as
>
> V_79 = Vertex(name = 'V_79',
> particles = [ P.Z, P.Z, P.H ],
> color = [ '1' ],
> lorentz = [ L.FF1 ],
> couplings = {(0,0):C.GC_59})
>
> After importing the model and generating a process, when I try to take the output, the following error is displayed
>
> AttributeError : 'ALOHAExpressionParser' object has no attribute 'f'
>
>
> Help regarding this will be highly appreciated.
>
> Thanks in advance.
>
> Regards,
> Sayan.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Sayan Dasgupta (sayandg) said : #2

There indeed was an error in my definition of the form factor.

Thanks a lot Olivier.

Regards,
Sayan.