MadGraph5_aMC@NLO

MadGraph as single particle generator

Asked by Antonio Policicchio

Hello
I would like to know if MadGraph can be used to generate single particles and simulate their decay.
This would be very useful for carrying out acceptance/efficiency studies e.g. in the contest of leptonjet searches with ATLAS/CMS.
The idea is to generate a sample of dark photons (massive spin 1 particles) that decay to fermions or scalars: we can vary the mass of the dark photon, its boost etc etc.

The Madgraph output can then be passed trough the full simulation of the detectors.

Many thanks for your support.

Best,
Antonio

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

Hi Antonio,

Sure this is possible.

For example, you can do:
generate z > l+ l-
output ZPROD

then go to ZPROD
and launch the generation of events:
./bin/generate_events

Each generation will be done for a fixed mass (that you can choose in the param_card). And all events will be written in the rest frame of the particle.

(Note that using the launch command in the mg5 interface will not work since it will only compute the partial width and will generate only a couple of events)

Cheers,

Olivier

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Antonio Policicchio (antonio-policicchio) said : 		#2

Hi Olivier,
many thanks for your swift answer which solves in part my question.
My question now is: it is possible generate e.g the Z with a given four-momentum and a given polarization?

Many thanks again!

Cheers,
Antonio

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Best Olivier Mattelaer (olivier-mattelaer) said : 		#3

Hi Antonio,

> it is possible generate e.g the Z with a given four-momentum?

No, this is not possible, you have to boost your events with an external program.

 and a given polarization?

You can modify the file
SubProcesses/PXXXXXXXX/matrix.f

in order to select which polarization to consider.

Cheers,

Olivier

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Antonio Policicchio (antonio-policicchio) said : 		#4

Thanks Olivier Mattelaer, that solved my question.