Number of arguments in FormFactor

Asked by teddym on 2020-08-17

Dear MadGraph Authors:
    I'm trying to use the second method in https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/FormFactors to write form factors for some loop-induced vertices. According to the description in the link, it said that I can put as many argument as I want for the form factors. So here is what I put at beginning:

VVSSF = Lorentz(name = 'VVSSF',
                 spins = [ 3, 3, 1, 1 ],
                 structure = 'FBox(P(-1,1)*P(-1,2), P(-1,1)*P(-1,3), P(-1,2)*P(-1,3), P(-1,3)*P(-1,3), P(-1,4)*P(-1,4) ) * (Metric(1,2)*P(-1,1)*P(-1,2) - P(2,1)*P(1,2))')

However, I got the error:

TypeError : 'LexToken' object has no attribute '__getitem__'

If I remove the last argument `P(-1,4)*P(-1,4)`, no error generated.

Is there any restriction here to prevent using fifth argument?

Thanks

YONGCHENG WU

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
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Solved by:
teddym
Solved:
2020-08-19
Last query:
2020-08-19
Last reply:
2020-08-19

Yes this is correct,

I pushed in this version:
https://bazaar.launchpad.net/~mg5core1/mg5amcnlo/2.7.4/revision/308
the limitation to 20 argument (I still fail to find a way to allow up to an infinite number of argument)

Cheers,

Olivier

teddym (niepanchongsheng) said : #3

Thanks Olivier!

20 arguments is enough!

Best
Yongcheng