Tune in Shower card for NLO generation

Asked by Amit Adhikary on 2019-04-27

Hi,

I have a query about using a specific tune while generating NLO events in Madgraph. To use a particular tune, I tried with the conventional setting i.e. "Tune: pp = 21" in the shower_card.dat (as compared to pythia8_card.dat during LO event generation). But it did not work. So, how should I fix a different tune while generating NLO events?

Also, this option Tune: pp = 21 sets "ATLAS A14 central tune with NNPDF2.3LO" from http://home.thep.lu.se/Pythia/pythia82html/Tunes.html. Is this also true if I use an NLO PDF i.e. NNPDF2.3NLO?

Thank you very much.

Best,
Amit

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
Paolo Torrielli Edit question
Last query:
2019-04-27
Last reply:
2019-04-29

Dear Amit,

in principle you can change some of the Pythia 8 settings by editing
the script MCatNLO/Scripts/MCatNLO_MadFKS_PYTHIA8.Script, which
is the one that actually writes the card read by Pythia at runtime.

Please, be aware that, by changing settings there, you may run the risk
of having an inconsistent setup with respect to the one used for generating
the events, in particular if the guidelines in "http://amcatnlo.web.cern.ch/amcatnlo/
-> Help and FAQs -> Special settings for the parton shower" are not respected.
Thus it is up to you to make sure that the tune you want to use does respect
those.

As for your second question, I don't know what the tune commands exactly
do in Pythia, namely whether the tune resets the pdf or not, probably it is
better if you contact the Pythia authors directly.

Cheers.
Paolo

Hi Paolo,

Thanks for your help and I will try to contact the Pythia authors.

Best,
Amit

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