Dear all,
There seems to be a mismatch in reconstructed photons between the “Photons” and “ReconstructedParticles” in FCC samples in EDM4HEP format. This issue has been raised in an old thread Photons at Delphes FCC-ee but there was no clear conclusion.
If we select photons from the ReconstructedParticles
using the Photon
index, i.e.
.Define("photons", "ReconstructedParticle::get(Photon0, ReconstructedParticles)")
all photons in this collect have energy > 2 GeV. This is expected as in the IDEA DELPHES the photon efficiency is set to 0 if they have energy < 2 GeV.
If the photons are selected from ReconstructedParticles
not with the Photon
index, but with ReconstructedParticles.type==22
, there is no cut-off of photon energy and the distribution extends to 0.
(Please note that these two plots are made from different sample files so the number of entries do not mean anything. But this behavior (distribution) is the same for different samples. The ones we checked are pythia Zee, Zmumu at 91 GeV, Whizard ttbar sample at 365 GeV, MadGraph Heavy Neutral Lepton samples at 91 GeV.)
I have two specific questions related to this.
- Is the presence of extra low energy photons in the
ReconstructedParticles
expected and reasonable? In comparison, the 2 GeV cut-off is also applied to electrons and muons in IDEA DELPHES, and those low energy electrons or muons are indeed cleaned from theReconstructedParticles
collection. - This is more related to FCCAnalysis. Nominally when we do jet clustering and missing energy calculation, we use the full
ReconstructedParticles
collection, i.e. including those low energy photons. Would this lead to an over-optimistic jet cluster or missing energy resolution?
Would be great if people could share more information/insight on this.
Best,
Xunwu