MadGraph5_aMC@NLO

Lorentz and color indices

Asked by lamrinjar

Can someone explain to me the format of the elements in lorentz.py? I couldn't find a summary elsewhere on the Internet.

For example, what does each object in the following mean?

FFV2 = Lorentz(name = 'FFV2',
               spins = [ 2, 2, 3 ],
               structure = 'Gamma(3,2,-1)*ProjM(-1,1)')

Similarly, what does the color structure stand for in vertices.py? Example --

V_747 = Vertex(name = 'V_747',
               particles = [ P.g, P.Z, P.su1__tilde__, P.su1 ],
               color = [ 'T(1,4,3)' ],
               lorentz = [ L.VVSS1 ],
               couplings = {(0,0):C.GC_279})

Thanks in advance!

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

Hi,

You can find the information in this paper:
arXiv:1108.2040

for the color convention, you can look at table 5.
for the lorentz convention you can look at table 6.

Cheers,

Olivier
On 23 Sep 2015, at 16:17, lamrinjar <email address hidden> wrote:

> New question #271716 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/271716
>
> Can someone explain to me the format of the elements in lorentz.py? I couldn't find a summary elsewhere on the Internet.
>
> For example, what does each object in the following mean?
>
> FFV2 = Lorentz(name = 'FFV2',
> spins = [ 2, 2, 3 ],
> structure = 'Gamma(3,2,-1)*ProjM(-1,1)')
>
> Similarly, what does the color structure stand for in vertices.py? Example --
>
> V_747 = Vertex(name = 'V_747',
> particles = [ P.g, P.Z, P.su1__tilde__, P.su1 ],
> color = [ 'T(1,4,3)' ],
> lorentz = [ L.VVSS1 ],
> couplings = {(0,0):C.GC_279})
>
> Thanks in advance!
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
lamrinjar (nraj) said : 		#2

Thanks Olivier Mattelaer, that solved my question.