GenJetFinder & FastJetFinder

[Roberto Franceschini]

Hello,

I see that in the default card of Delphes there are two jet makers. Which one is used in the end? how these two jet makers interact with each other?

I would like to ask how jets are made and what jets (GenJet or FastJet) end up in the LHCO output.

Thanks for your reply.
Roberto

[Ezequiel Alvarez]

Hi,

I'm also interested in this question, and 2 more questions:

1) I wonder if is there a way to use the Delphes card to reconstruct the jets at particle level and see its result without going through the detector simulation.

2) The same for the leptons, is there a simple way of seeing which are the isolated leptons at particle level? (Without including detector simulating effects.)

I would like this to be in a branch so I can analyse it using Root.

Thanks, Ezequiel.

[Michele Selvaggi]

Hi,

the two jet finders do not interact, as they act on different 4-vectors collections.
a) GenJetFinder uses all stable particles (after ps+hadronization) without any detector simulation and produces collection "GenJet"
b) FastJetFinder uses reconstructed particles and produces collection "Jet"

They both use the fastjet package to reconstruct jets.
To see which parameters are used by default you can have a look at the detector card you are using (probably examples/delphes_card_CMS.tcl or examples/delphes_card_ATLAS.tcl).

In the lhco file you have access to b) only.

For the gen leptons, I guess the easiest way is to extract them from the "Particle" branch, which contains all gen level particles, both stable and unstable.

Michele