Opened 7 years ago
Last modified 7 years ago
#1152 new How to
JetDeltaPt from examples/Example3.C
| Reported by: | Dongsub Lee | Owned by: | |
|---|---|---|---|
| Priority: | major | Milestone: | |
| Component: | Delphes code | Version: | Delphes 3 |
| Keywords: | Jet, JetConstituents, JetDeltaPt | Cc: |
Description
Dear Delphes team,
Hi.
I checked the JetDeltaPt which is normalized(by pT of a jet) difference between pT of summation of all constituents of jet and a pT of jet itself is not centered at 0 and have quite large discrepancy, around 15% for simple p p > j j samples which is generated by MG5 and showered by Pythia8.
I saw that discrepancy by my own code first, and I also saw the same thing happens with examples/Example3.C.
I simply ran Pythia8 and Delphes in pipe line of MG5 with default Delphes card(delphes_card_ATALS.dat) after replacing input array of jet finder to EFlowMerger/eflow from Calorimeter/towers.
Currently I'm using Delphes v3.4.1, and I addressed all branches of delphes_events.root in my code.
I've checked that whether I correctly accessed all constituents of a jet or not, but I think that I did not make that kind of mistake.
So here is my question.
1.
If it is not a usual situation, then did I missed some constituents of a jet?
I mean, is there any constituents which is not included in the TRefArray of Jet->Constituents but clustered as a jet by FastJet?
2.
If not, so that it is usual case, then is it okay to use such jets having pT discrepancy with its constituents?
Can I assure that there is nothing I missed?
Attachments (2)
Change History (4)
by , 7 years ago
| Attachment: | jet_delta_pt.png added |
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comment:1 by , 7 years ago
I uploaded result plot and Delphes card used in simulation.
The uploaded plot was drawn with around 13k events(I got 13k events after merging 50k events by Pythia8).
So, there would be, roughly, more than 20k jets used for the plot.
Because of the size limit of file I couldn't upload a sample, but you can easily(and quickly; it would not take long time) reproduce sample with MadGraph5.
I used sqrt(s) = 14TeV and didn't change anything from MadGraph5 configuration.
Event process is [ p p > j j ]
comment:2 by , 7 years ago
Most likely it is because a jet energy scale is applied:
https://github.com/delphes/delphes/blob/master/cards/delphes_card_ATLAS.tcl#L630-L640
can try putting the value to 1 in the ScaleFormula ?
That is happens simply because the Jet momentum is rescaled but not the jet constituents.
Result from DELPHES/examples/Example3.C