MadGraph5_aMC@NLO

Cross sections with definite helicity configurations

Asked by Adil Jueid

Dear,

I would like to know how I can generate events with definite polarizations in the final states.
Say for example, I would like to collide two protons to produce a top and anti-top where the
top quark has a spin up and the anti-top is spin down. With the spin projection is with respect
to certain axis which is chosen to maximize certain probabilities.
Also, Is it possible to define the axes and to change the axis from one frame to another
in Madgraph.

Thanks a lot for your help,
Adil

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

Hi,

Here is the information that you need.
Concerning the definition of the helicity, you need to refer to the HELAS manual, and you can modify the associate function (in Source/DHELAS) in order to change the axis of reference.

Cheers,

Olivier
FAQ #2243: “How to generate polarized particles.”.

Revision history for this message
Adil Jueid (ajueid) said : 		#2

Hi,

Thanks a lot.
This solved my problem although I haven't look for the spin axis definition in Source/DHELAS.
But I succeeded in generating events with definite helicity configurations.

Cheers,
Adil