MadGraph5_aMC@NLO

Madgraph5 specific diagram production for cross section analysis

Asked by Liliana on 2020-11-14

I need to produce an specific subprocess for u d~ >e+ ve u u~ g .

I haven't been capable of producing just one specific diagram, is this possible? I get 24 diagrams but I need to analyse just one process. If not, is there a way of differenciating between subprocesses? All I need is the Cross section of this specific feynman diagram (for example diagram 19) and I get all the Cross sections in the html file but they are called G1 G3 ... Etc and I cannot know which one corresponds to the diagram I wanna study.

I appreciate your help, I rlly have been trying everything.

Question information

Language:: English Edit question

Status:: Answered

For:: MadGraph5_aMC@NLO Edit question

Assignee:: No assignee Edit question

Last query:: 2020-11-14

Last reply:: 2020-11-15

Link existing bug

Revision history for this message

Olivier Mattelaer (olivier-mattelaer) said on 2020-11-15:

Diagram #19 is not gauge invariant and therefore the computation of the cross-section of the diagram alone is not a physical quantity. Additionally, since the choice of gauge in MG5aMC depends of the frame such cross-section will not be lorentz invariant.

> and I get all the Cross sections in the html file but they are called G1 G3 ... Etc and I cannot know which one corresponds to the diagram I wanna study.

Those numbers do not correspond to the integration of single diagram but of rather complex quantity --related to some diagram--. Those quantity are alone also not lorentz/gauge invariant but are construct in a way that their sum is
gauge and lorentz invariant (and that it equals to the full cross-section including interference term.

This being said here is the documentation between the link of channel and diagram:
https://answers.launchpad.net/mg5amcnlo/+faq/2944
(likely to change in a future version of the code)

and this is the link on how select Feynman diagrram:
https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/FAQ-General-15

Cheers,

Olivier

> On 14 Nov 2020, at 21:05, Liliana <email address hidden> wrote:
>
> u d~ >e+ ve u u~ g