Opened 6 years ago
Last modified 5 years ago
#1385 new How to
Phi correction to tracks (bremsstrahlung applied also to charged hadrons?)
| Reported by: | jerdmann | Owned by: | |
|---|---|---|---|
| Priority: | minor | Milestone: | |
| Component: | Delphes code | Version: | Delphes 3 |
| Keywords: | Cc: |
Description
Dear Delphes experts,
using the card delphes_card_CMS.tcl, only the pT of charged-hadron tracks should be smeared, not any other track parameters, if I understand it correctly. Indeed, the eta comes out right:
PID: 211 (pi+)
truth eta: 1.8733015
truth phi: -0.589060
=> track eta: 1.8733015
=> track phi: 0.555576
PID: -211 (pi-)
truth eta: 1.9796019
truth phi: -0.551807
=> track eta: 1.9796019
=> track phi: -0.659747
So, it looks a little suspicious to me that the eta values are unchanged, but the phi values are. Could this be due to bremsstrahlung effects that are (erroneously) applied also to charged-hadron tracks and not only to electron tracks? Indeed, the corrections for pi+ and pi- in this example go in the opposite direction...
This ticket is related to https://cp3.irmp.ucl.ac.be/projects/delphes/ticket/1384, but I have posted it separately, because I am not confident that it is a bug, but perhaps rather a misunderstanding on my side. Indeed, I could only get a reasonable resolution for two-track resonances in ticket 1384 when I used the original particles's phi instead of the track phi.
Cheers and thanks for your help,
Johannes
P.S.: I am using Delphes 3.4.1.
Change History (2)
comment:1 by , 6 years ago
comment:2 by , 5 years ago
Hi again,
I think the following commit should fi the behaviour you are observing.
https://github.com/delphes/delphes/commit/79d4123bb79c316d1345f106e6386b5abd25a398#diff-0ffd71466c693df51b1910bff2455cb6
Can you take the latest version on github?
A quick follow-up:
I think that I have understood by now that bremsstrahlung is not implemented in Delphes. So, that was obviously not the right guess. However, I have also further found that the different phi between track and particle appears to be happening only for tracks that do not start at the primary vertex but originate from the decay of another particle that travels some distance before decaying. I hope that this helps to point me to the origin of the difference in phi.
Cheers,
Johannes