MadGraph5_aMC@NLO

Syntax Issues on pp Elastic Scattering with Bremsstrahlung Photon

Asked by Max Fieg

Hello Experts,

I am trying to study the Bremsstrahlung process, p p > p p a, but I think I am having some minor syntax issues right now. Eventually I will make this a dark brem process, but I want to make sure the SM version is correct.

I want each proton to stay intact, so I think I am to use lpp1=2,lpp2=2, and replace the initial state protons with photons, based on your answer here https://answers.launchpad.net/mg5amcnlo/+question/282131

i.e. I think I would enter:
add process a a > p p a
,is this correct?
I am interested in forward production, and because of this, this process takes a very long time. Maybe if I give some small maximum pseudorapidity cut for the photon I can speed this up?

My first naive guess was p p > p p a. But when I use lpp=2, I get some "segmentation fault" errors that look like this person's question https://answers.launchpad.net/mg5amcnlo/+question/697809. I can paste the debug log but I don't think this syntax is correct anyway, so I'll leave it off for now

Thank you in advance. I think this is probably a very simple/dumb question, but I can't seem to find a previous answer to my question. I appreciate your time.

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

I guess that you need a new UFO model where you have p as a particle of your model that has QED interaction.
let call that particle by his pdf 2212
then you can do
2212 2212 > 2212 2212 a
and set lpp1=lpp2=0

You can technically use the "sm" model and change the pdg code of the tau to 2212 and set his mass to the proton mass
(which is the same as modifying the mode but by hand)

Cheers,

Olivier

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