MadGraph5_aMC@NLO

Photon-induced processes inconsistency

Asked by Maura Barros

Dear experts,

I've been using MadGraph to generate photon-induced processes. I am using a new UFO model for BSM and I noticed some differences between MadGraph versions 2.x and 3.x. In this specific case, I used versions 2.6.7 and 3.5.1. We were expecting a specific cross-section scaling with the coupling and that the kinematics changed with the mass of the new particles but not with the couplings.
However, this was not observed with the new 3.5.1 MG version. The cross-section scaling and kinematics were not as expected. When I moved to version 2.6.7 I noticed that the cross-section scaling and kinematics were as expected.
Even comparing cross-sections from both versions I get a factor of 10 difference between both of them. Is this a known issue? Is there any specific recommendation for which version to use in the case of generating photon-induced processes?

Thank you!

Best regards,
Maura

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

photon induced process can means a lot of things (elastic/inelastic from an electron/muon/proton beam or laser setup,...) , and therefore I have no clue of what you are speaking about.

The best would be that you do fill a bug report (and not a question like here where not attachment are allowd) and that you do provide the information to reproduce the run. which include the
proc_card (or command that you use to generate the code)
and the run_card (setup of your beam/...) This will allow me to comment.

This being said
1) version 2.6.7 is not supported and will likely not run/compile anymore on any of our test machine. In any case I will test first on our LTS version (2.9.17)
2) The default run_card/(beam setup) will likely be quite different between 2.6.7 and 3.5.2. So this can explain a lot of difference
3) 2.9.0 introduces new method of integration, which might be activated for your process (or not) if this is the issue/problem, you can easily revert to the other method of integration.

Cheers,

Olivier

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Maura Barros (maurabarros) said : 		#2

I am sorry, I should have been more specific... I will create a bug report, add more details and attach what is needed! Thank you!

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