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CLD fullsim for FCCee: muon->pion misidentification at 2-7 GeV using PandoraPF #52

Open mcepeda opened 6 days ago

mcepeda commented 6 days ago

Dear all,

I am working on tau reconstruction using full simulated samples with CLD, starting from Pandora PFOs.

I have noticed a sizeable contamination of muons in my analysis: these are muons originating from tau decays which are identified as pions by Pandora, concentrated between 2 and 7 GeV and at central Theta. This is using the "PandoraPFOs" sample (image attached) , and I see a similar tendency with "TightSelectedPandoraPFOs". Note in the image there are also muons below 2 GeV and a small leakage at high momentum at Theta=pi/2: those are not an issue.

@Zehvogel pointed me to a difference in muon algorithm starting at 7 GeV, which should explains this behaviour:

https://github.com/PandoraPFA/LCContent/blob/master/src/LCPlugins/LCParticleIdPlugins.cc#L434 (LCMuonId) https://github.com/PandoraPFA/LCContent/blob/master/src/LCParticleId/MuonReconstructionAlgorithm.cc

Is there an easy way to tune the settings of the Muon ID in Pandora, eg changing the threshold to start at 5 GeV ? If there is any documentation about how to tune this I can do a check.

Alternatively, any further tweaks on how to improve the muon ID at low momentum would be great.

More plots are on the way (requested by @BrieucF ), I will update the ticket as soon as they are ready.

Regards,

María Cepeda

muonpion_pandoraPFO

andresailer commented 6 days ago

https://github.com/PandoraPFA/LCContent/blob/aabb475ab87a538826befb36e79e27bc977e321f/src/LCParticleId/MuonReconstructionAlgorithm.cc#L28

    m_minTrackCandidateEnergy(7.f),

Add after https://github.com/key4hep/CLDConfig/blob/f265f3d01f9b1ba8aae8f10692495c91d218bff4/CLDConfig/PandoraSettingsCLD/PandoraSettingsDefault.xml#L69

<MinTrackCandidateEnergy> 5.0 </MinTrackCandidateEnergy>
Zehvogel commented 4 days ago

Just adding some old plots that I dug out showing muon PID efficiency and purity for the ILD detector. There the MuonReconstructionAlgorithm is enabled from 4 GeV but the efficiency is degraded in the barrel up to ~10 GeV. The LCMuonId running below 4 Gev produces many fake muons (at least for ILD) .

mu_eff_pandora.pdf mu_pur_pandora.pdf

If the efficiency of the MuonReconstructionAlgorithm is too low for your purposes you can also try to relax the matching criteria of muon system clusters to tracks which should be these parameters.

    m_maxDistanceToTrack(200.f),
    m_minHelixClusterCosAngle(0.98f),