MadGraph5_aMC@NLO

isr and beamstrahlung in lepton collider

Asked by Yehia Abdelaziz

I am trying to generate events in ee collider while implementing isr and beamstrahlung for the ilc using the following commands:

set pdlabel ilc500ll
set lpp1 -3
set lpp2 +3

The problem is that after madgraph run, I look at the lhe file but I don't see any photons. Why is that? Shouldn't the photon that is radiated from the electrons appear in the lhe file?

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

The effect of both ISR and beamstrahlung is integrated over and therefore not appearing in the file.
In principle the role of the parton-shower would be to pass from inclusive radiation to exclusive radiation but the parton-shower has the issue to disantangle ISR from beamstrahlung.
So we would need someone to add one photon for the beamstrahlung (collinear) such that the parton-shower can handle to convert the inclusive event for the ISR to exclusive event.

So this is half normal and half problematic but at most you would get one photon (maybe one for each beam direction) to handle the beamstrahlung.

Cheers,

Olivier

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