Problems encountered when calculating deep inelastic scattering with MadGraph+Pythia

Asked by Qiji Xin on 2021-05-16

Hi,

I am using MadGraph (3.1.0) + Pythia8 to calculate fixed target neutrino deep inelastic scattering.
The MadGraph part works well, using the settings in https://answers.launchpad.net/mg5amcnlo/+question/678937 . MadGraph gives correct cross sections and lhe events.
The Pythia8 is loaded correctly by MadGraph.
However, after the Pythia8 run is done, I found Pythia8 doesn't generate any events.
I used Enu = 1e6 GeV and proton at rest (Ep = 0.938 GeV).

Then I tried Enu = 1e3 GeV and Ep = 1e3 GeV. Same CM energy as above, but Pythia can generate lots of events.
Then I have tried other different energies of Enu and Ep, and found that whether Pythia can generate events depend mainly on Ep but also on CM energy.
Then a friend told me that this is probably because MadGraph or Pythia has a minimum threshold of pT to do hadronization. If so, is there a way to change the minimum threshold of pT? If not, what could be the reason for the above?

Thanks very much!

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Olivier Mattelaer (olivier-mattelaer) said :
#1

This should be on the pythia side.
I can not comment on such issue.

If pythia author's indicate an issue on our side then please tell us and we can see what we can do.

Olivier

> On 16 May 2021, at 23:35, Qiji Xin <email address hidden> wrote:
>
> New question #697090 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/697090
>
> Hi,
>
> I am using MadGraph (3.1.0) + Pythia8 to calculate fixed target neutrino deep inelastic scattering.
> The MadGraph part works well, using the settings in https://answers.launchpad.net/mg5amcnlo/+question/678937 . MadGraph gives correct cross sections and lhe events.
> The Pythia8 is loaded correctly by MadGraph.
> However, after the Pythia8 run is done, I found Pythia8 doesn't generate any events.
> I used Enu = 1e6 GeV and proton at rest (Ep = 0.938 GeV).
>
> Then I tried Enu = 1e3 GeV and Ep = 1e3 GeV. Same CM energy as above, but Pythia can generate lots of events.
> Then I have tried other different energies of Enu and Ep, and found that whether Pythia can generate events depend mainly on Ep but also on CM energy.
> Then a friend told me that this is probably because MadGraph or Pythia has a minimum threshold of pT to do hadronization. If so, is there a way to change the minimum threshold of pT? If not, what could be the reason for the above?
>
> Thanks very much!
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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