simulating photon photon collision in madgraph

Asked by Siddharth

Hi,
      In the madgraph run card I see the option to do photon photon collision within EPA , but is there a way to simulate back-scattered laser photon using madgraph ?

thanks and regards

Siddharth

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Olivier Mattelaer (olivier-mattelaer) said :
#1

Hi,

This is not in the official version.
In the past I have implement the function following a request of a user, I asked him to validate the implementation but never get any feed back so I never include it in the official version.
You can find that version by running the following command:
bzr branch lp:~maddevelopers/mg5amcnlo/laser_beam_option

I have no clue if it works or not, so please give me feedback.
(This mode is encoded as option 4)

Cheers,

Olivier

On 18 Sep 2017, at 07:54, Siddharth <<email address hidden><mailto:<email address hidden>>> wrote:

New question #658191 on MadGraph5_aMC@NLO:
https://answers.launchpad.net/mg5amcnlo/+question/658191

Hi,
     In the madgraph run card I see the option to do photon photon collision within EPA , but is there a way to simulate back-scattered laser photon using madgraph ?

thanks and regards

Siddharth

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Siddharth (dwivedi-siddharth) said :
#2

hi,
      I tried implementing the photon photon collision in back scattered laser following the above suggestion . There are few observations.

1 ) The run card of the process directory did not have an explicit option 4 but when I put the switch to 4 it runs the process. I tried
a a > b b~ h.

2) Only a small fraction of events requested are generated. Say out of 50000 events only around 450-600 events are generated.
This is happening with SM model also and a bsm model that I am using.

3) I am not sure how to exactly validate the cross section values against another interface, say for example calchep.

thanks and regards

Siddharth

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said :
#3

Hi,

Thanks for the feedback,

1 ) The run card of the process directory did not have an explicit option 4 but when I put the switch to 4 it runs the process. I tried
a a > b b~ h.

That's correct.

2) Only a small fraction of events requested are generated. Say out of 50000 events only around 450-600 events are generated.

This indicate a Phase-space integration problem. One should be smarter than our default integration scheme for the integration.
Changing the PS integration is possible but will require a lot of time.

3) I am not sure how to exactly validate the cross section values against another interface, say for example calchep.

If I remember correctly, SHERPA has such mode implemented. Since I would not have the dedicated PS implemented in a short time line, I would advise to try the SHERPA implementation.

Cheers,

Olivier

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