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Opened 10 years ago

Last modified 7 years ago

#548 new How to

External FastJet

Reported by: iris Owned by:
Priority: critical Milestone:
Component: Delphes code Version: Delphes 3
Keywords: Cc:

Description

Hi, I am completely new to this tool. I am using the MG5+Pythia+Delphes package.

I am trying to reproduce some published results using the MDF(mass drop filter) method. What should I do to change the FastJet code inside Delphes? Where can I find the initial code? Seems I need to run Delphes with external FastJet code?

Thanks in advance!

Change History (9)

comment:1 by iris, 10 years ago

Priority: minorcritical

comment:2 by Pavel Demin, 10 years ago

Hi,

I'm not sure if I understand your questions correctly (for instance, what do you mean by "the initial code"?).

Anyway, there are two possibilities to use a different version of FastJet:

  • run Delphes with external FastJet as described in

https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook/ExternalFastJet

  • replace FastJet that comes with Delphes by your version of FastJet using update_fastjet.sh:
    cd external
    rm -rf fastjet
    source ../doc/update_fastjet.sh
    

You'll most probably need to slightly modify update_fastjet.sh.

Cheers,

Pavel

comment:3 by iris, 10 years ago

Thanks!

By "initial code", I mean the code of FastJet used in Delphes since I just want to change a bit rather than rewriting the whole thing.

So anyway I need to install FastJet instead of changing something inside Delphes?

Thank you so much!

comment:4 by Pavel Demin, 10 years ago

The code of FastJet used in Delphes can be found in the external/fastjet directory. I don't see any problem to change it in place.

When I proposed the two solutions, I thought that you have already a version of FastJet that you want to use with Delphes.

comment:5 by iris, 10 years ago

Thank you! I should state the question more clearly.

When dealing with the branch "Jet" in Delphes, can I undo the clustering?

To be precise, actually I need to undo the clustering and deal with the subjets. I dont know whether I should change the code in FastJet or analyze the resulting jets in Delphes root file (if so, how to undo the clustering to obtain the subjets?) ?

Last edited 10 years ago by iris (previous) (diff)

comment:6 by iris, 10 years ago

Hello, I found this on web and it is exactly the code I want:

http://www.lpthe.jussieu.fr/~salam/fastjet/repo/doxygen-3.0alpha3/11-boosted__higgs-new_8cc_source.html

My question is where I should paste it?

comment:7 by Michele Selvaggi, 10 years ago

Hi,

my suggestion is that you have a separate Delphes and FastJet installation.
You have very detailed instructions for running FastJet using Delphes as an external library here:

https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook/ExternalFastJet

After you did everything explained there, you can then simply modify the examples !ExternalFastJetHepMC.cpp or ExternalFastJetBasic.cpp
by plugging in the fast jet code you mentioned above.

Cheers,
Michele

Last edited 10 years ago by Michele Selvaggi (previous) (diff)

in reply to:  6 comment:8 by Jewel, 7 years ago

Replying to iris:

Hello,

I am doing some event generation using MG5+Pythia+Delphes packages.
Now, I am trying to reproduce higgs invariant mass using mass-dropp tagging method.
How I compile that Fastjet (.cc file) and Delphes root file.
How I reproduce higgs invariant mass plot?
Thanks in advance.

comment:9 by Michele Selvaggi, 7 years ago

Hi,

you'll have to:

  • produce an hepmc file with madGraph
  • install standalone Delphes version
  • follow instructions here:

https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook/ExternalFastJet

This allows you to run Delphes with your own fastjet code.

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