Full number of events not generated

Asked by Siddharth on 2017-08-01

Hi,

1) I am using a model file having an anomalous Higgs vertex, h-b-bbar-gamma (from a higher dimensional operator) in Madgraph.
I am using it to simulate a a > b b~ b b~ in e+ e- collider using the following switch:

        3 = lpp1 ! beam 1 type
        3 = lpp2 ! beam 2 type

When I set the BSM coupling parameters to zero and demand , say 50000 events in generation, I get all the points generated. But when I set the BSM parameters to some non-zero but high values, I get only around ~900 points generated. This gets corrected when I reduce the value of the BSM parameters.
I initially thought that less number of events generated means some singularities in the phase space, which Madgraph skips when generating events. But I have ptj, ptb > 20 GeV and delta_R > 0.4 cuts in run card. So I cannot understand what could be the problem Could you please help with the same ?

2) On a related subject, if i am not wrong, the switch 3 in the above setting refers to effective photon approximation. But is there a way to change the run card to simulate a back scattered photon in a "photon collider" ?

thanks and regards

Siddharth
.

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
2017-08-01
Last query:
2017-08-01
Last reply:
2017-08-01

Hi,

> 1) I am using a model file having an anomalous Higgs vertex, h-b-bbar-gamma (from a higher dimensional operator) in Madgraph.
> I am using it to simulate a a > b b~ b b~ in e+ e- collider using the following switch:
>
> 3 = lpp1 ! beam 1 type
> 3 = lpp2 ! beam 2 type
>
> When I set the BSM coupling parameters to zero and demand , say 50000 events in generation, I get all the points generated. But when I set the BSM parameters to some non-zero but high values, I get only around ~900 points generated. This gets corrected when I reduce the value of the BSM parameters.
> I initially thought that less number of events generated means some singularities in the phase space, which Madgraph skips when generating events. But I have ptj, ptb > 20 GeV and delta_R > 0.4 cuts in run card. So I cannot understand what could be the problem Could you please help with the same ?

This means that you hit the maximum efficiency limit of our phase-space integrator.
We are starting to create a newly designed phase-space integrator to help for those kind of issue but this project is still at his beginning and will not be ready any time soon.
So the only solution that you can try is multi-run.

> 2) On a related subject, if i am not wrong, the switch 3 in the above setting refers to effective photon approximation. But is there a way to change the run card to simulate a back scattered photon in a "photon collider" ?

Now we do not have any PDF associate to such mode. I would suggest to check for Sherpa.

Cheers,

Olivier

> On 1 Aug 2017, at 17:17, Siddharth <email address hidden> wrote:
>
> New question #654447 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/654447
>
> Hi,
>
> 1) I am using a model file having an anomalous Higgs vertex, h-b-bbar-gamma (from a higher dimensional operator) in Madgraph.
> I am using it to simulate a a > b b~ b b~ in e+ e- collider using the following switch:
>
> 3 = lpp1 ! beam 1 type
> 3 = lpp2 ! beam 2 type
>
> When I set the BSM coupling parameters to zero and demand , say 50000 events in generation, I get all the points generated. But when I set the BSM parameters to some non-zero but high values, I get only around ~900 points generated. This gets corrected when I reduce the value of the BSM parameters.
> I initially thought that less number of events generated means some singularities in the phase space, which Madgraph skips when generating events. But I have ptj, ptb > 20 GeV and delta_R > 0.4 cuts in run card. So I cannot understand what could be the problem Could you please help with the same ?
>
> 2) On a related subject, if i am not wrong, the switch 3 in the above setting refers to effective photon approximation. But is there a way to change the run card to simulate a back scattered photon in a "photon collider" ?
>
>
> thanks and regards
>
> Siddharth
> .
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Siddharth (dwivedi-siddharth) said : #2

Thanks Olivier Mattelaer, that solved my question.