Opened 8 years ago
Last modified 7 years ago
#1121 new How to
Btagging, What should I use
| Reported by: | haolin | Owned by: | |
|---|---|---|---|
| Priority: | minor | Milestone: | |
| Component: | Delphes code | Version: | Delphes 3 |
| Keywords: | BTaggin | Cc: |
Description
Hi,
I encounter a problem in btagging:
In the delphes card(FCChh.tcl) I set the BTagging BitNumber = 0.
Then, in the output root file, the BTag of a jet(jet->BTag) could be larger than 1.
So, should I use "if(jet->BTag)" or "if(jet->BTag & (1 << 0))" to determine a jet is a B jet? The two approach gives different result.
Thanks,
Haolin
Change History (4)
follow-up: 2 comment:1 by , 8 years ago
comment:2 by , 8 years ago
Got that. Thans very much for your quick reply.
BTW, actually I am courious how BTag is written into the root file, why it can be larger than 1? Since in DelphesClasses\.h, it says "0 or 1 for a jet that has been tagged as containing a heavy quark."
Also could you remind me how jet->Flavor is determined in Delphes?
Replying to mselvaggi:
Hi,
the second one, as explained here:
https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook/Modules#BTagging
Michele
follow-up: 4 comment:3 by , 7 years ago
It can be larger than one because you can specify several b-tagging algorithm and store the outcome of each one into its own personal bit.
In the FCChh card that you are using the second tag (BitNumber = 1) is dedicated to c-tagging.
https://github.com/delphes/delphes/blob/master/cards/FCC/FCChh.tcl#L733
The Jet flavour is computed by checking the parton PID that is the closest in DR to the reconstructed jet. Priority is given to highest PID.
comment:4 by , 7 years ago
Thank you very much for your reply.
Sorry, one additional question.
Can The vaule of BTag be different on different operating systems? Since although I use the identical anaylsis code for the same root file, it gives different values of BTags. One of them gives very bizzare large value, the other seems to give some more reseanalbe value like 0,1,2,3.
Replying to mselvaggi:
It can be larger than one because you can specify several b-tagging algorithm and store the outcome of each one into its own personal bit.
In the FCChh card that you are using the second tag (BitNumber = 1) is dedicated to c-tagging.
https://github.com/delphes/delphes/blob/master/cards/FCC/FCChh.tcl#L733
The Jet flavour is computed by checking the parton PID that is the closest in DR to the reconstructed jet. Priority is given to highest PID.
Hi,
the second one, as explained here:
https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook/Modules#BTagging
Michele