Status of the studies on e/gamma ID, performance, and selection

LPSC - Grenoble Julien MOREL 1Status of the egamma studies

Electron ID & Perf Photon ID & Perf EM Cluster ID at high Conclusion

Status of the studies on e/gamma ID, performance, and Status of the studies on e/gamma ID, performance, and selectionselection

Julien MOREL

Exotic meeting

19 July 2007



OutlineOutline

Electron and DiElectron identification and performanceElectron and DiElectron identification and performanceZ’Z’ee at 1 TeVee at 1 TeV

Photon identification and performancePhoton identification and performanceGGgg at 500 GeVgg at 500 GeV

EM cluster identification at very high EM cluster identification at very high

Conclusion and outlookConclusion and outlook



Electrons and diElectronsElectrons and diElectrons



Dataset and Athena versionDataset and Athena version

Athena versionAthena version : 12.0.6

ProcessProcess : Z’e+e- at 1TeV (Mll > 500 GeV)

Data SetData Set : Correction of the 1mm bug have been appliedtrig1_misal1_csc11.005605.Zprime_ee_pythia_chi1000.merge.AOD.v12000604_tid010014._00001.pool.root.2trig1_misal1_csc11.005605.Zprime_ee_pythia_chi1000.merge.AOD.v12000604_tid010014._00002.pool.root.3trig1_misal1_csc11.005605.Zprime_ee_pythia_chi1000.merge.AOD.v12000604_tid010014._00004.pool.root.3trig1_misal1_csc11.005605.Zprime_ee_pythia_chi1000.merge.AOD.v12000604_tid010014._00005.pool.root.2

Number of eventsNumber of events : 7250 Z’eeWe use electrons coming from the Z’ matched with the truth

Cross sectionCross section = 376.5 fb



Basic kinematics plotsBasic kinematics plots

Due to Z’ Pic at 1 TeV

Cut at 500 GeV Due to Z’ Pic at 1 TeV



Electron selection criteria and efficiencyElectron selection criteria and efficiency

To compute the electron selection efficiency, we ask : •A matching with the truth•An IsEm criteria (Loose, Medium or tight) •An isolation criteria (ETcone20 / ET< 20%)

Loose : IsEM & 0x7 ==0Medium : IsEM & 0x3FF ==0

Tight : IsEM ==0

Crack 1.4 – 1.5

Average efficiency of 95% for loose electrons and around 80% for medium electrons

Eff

icie

ncy

Eff

icie

ncy



Electron selection criteria and efficiencyElectron selection criteria and efficiency

Results for tight electron : splitting the different bit of IsEm up to IsEm == 0

Identification based onTRT and E/P are themain sources of loss.

E/P loss increase with pT

Average efficiency around 60% after isolation cut for tight electrons



Electron resolution and linearityElectron resolution and linearity

We can compute the resolution and linearity for the selected electrons :

Central Crack End-Cap

Tight electrons

Resolution :barrel ~ 1.3%crack ~ 5.3%endcap ~ 1.3%

Linearity :barrel ~ -0.07%crack ~ 7%endcap ~ 0.14%

These performances are quite independent

of the electron identification criteria(loose, medium, tight)



The “best” electron selectionThe “best” electron selection

In order to choose the “best” electron selection :

Electrons resolution and linearity does not depend on the selection criteria

We will keep the selection which provide the best efficiency on signal and the best rejection on background.

We have to look at high pT dijet to conclude.



DiElectron pairs selection criteria and efficiencyDiElectron pairs selection criteria and efficiency

Loose

Medium

Tight

Dielectron pairs selection cuts :•2 gene elec with ||<2.5•2 reco elec•2 reco elec with opp ch•IsEM

Average eff ~50%

Average eff ~40%

Average eff ~20%



DiElectron mass resolution and linearityDiElectron mass resolution and linearity

Resolution = (0.82 ± 0.02) %Linearity =(0.07 ± 0.02) %

Resolution = (0.84 ± 0.03) %Linearity =(0.15 ± 0.04) %

Poor reconstruction and linearity if one of the electron goes in the crack but it concern few events

Z' mass Resolution and Linearity does not strongly depend on different IsEM cut (loose, medium or tight electrons)

Barrel -Barrel Crak -Crak Barrel - EndCap

Tight electrons



PhotonsPhotons



Dataset and AthenaDataset and Athena

(Kamile Dindar, Bob Kehoe and Haleh Hadavand)

Athena versionAthena version : 12.0.6

HighPtView-00-00-30HighPtView-00-00-30

ProcessProcess : G (500 GeV) 4500 events

Data SetData Set :trig1_misal1_mc12.005623.Ggammagamma_500_pythia.recon.AOD.v12000601_tid006263trig1_misal1_csc11.005310.PythiaH120gamgam.recon.AOD.v12000502_tid005427



HighPTView - Photon cuts and photon selection efficienyHighPTView - Photon cuts and photon selection efficieny

HighPt-view30 photon selection criteria :•useIsEM = False•useShowerShapes = True •useIsolation = True•ID cuts (baseline photon ID cuts determined by the egamma group)•etCut = 15 GeV •deltaRCut = 0.1•isolationCone = 0.45•absoluteIsolationCut = 10 GeV•UseTrackIsol = False•RemoveOverlapWithSameType = False

Fake diPhoton :With a dijet sample with 5350 events, using theses photons selection cuts (without isolation and IdCuts), 516 events with diphoton are selected.



Photon kinematic distributionsPhoton kinematic distributions

pT, , and E distribution for gamma coming from 500 GeV Graviton

Generation

Reconstruction



Photon selection efficiency for photon coming from 500 GeV GravitonPhoton selection efficiency for photon coming from 500 GeV Graviton

Central

pT (GeV)

pT (GeV)

Mean = 0.884±0.003

Mean = 0.786±0.004

Mean = 0.652±0.005

Mean = 0.902±0.003

End-cap

Central

End-cap

isolation offno ID cuts

isolation offno ID cuts

isolation onwith ID cutsDrop at high pT

isolation onwith ID cutsDrop at high pT



EM clusters at high EM clusters at high



Dataset and Athena versionDataset and Athena version

(Ning Zhou and John Parsons)Athena versionAthena version : 12.0.6

Data Set :Data Set :Process : 5144 Zee Ze+e-

BackGround : 5802 JF17 Filter Dijet

Number of eventsNumber of events :In 5144, there are 195k clusters with a matching ( dR<0.2 ) to Truth Z decay electrons,

in which 110k clusters are in EMEC and 85k clusters are in FCAL.In 5802, there are 325k clusters in EMEC and 271k clusters in FCAL.

Region of interest Region of interest = = Large Large region region ::EMEC : 2.5 < < 3.2 FCAL : 3.2 < < 5.0

•Selection of topocluster with |Selection of topocluster with ||>2.5 and 20GeV<Et<60GeV from |>2.5 and 20GeV<Et<60GeV from CaloCalTopoClusterCaloCalTopoCluster



Goal of the study Goal of the study

In ATLAS, only || < 2.5 range is fully reconstructed as egamma objects. However, out of it, electrons could be approximated by EMlike clusters.

The goal of the study is to find a way to identify EMlike Cluster in order to reconstruct events with very large electron (>2.5). The large QCD background imposes a powerful method to identify EMlike Cluster.

There is a reco energy bias for EMlike clusters in FCAL :

Et shift ~ 15%

TopoCluster compared with matched Truth Z decay electron



EM cluster identification methodEM cluster identification method

To identify EMlike clusters a Multi Variate Analysis is used :A Boost Decision Tree dealing with cluster moments

(you can find the definition of the cluster moments on the silde5 of Ning’s talk given at egamma on the 05/060/07 or in Backup Slides)

In EMEC: id_bdt > 0.2 90% EMEC clusters from Zee sample and 3.2% from Dijet sample pass the cut.In FCAL : id_bdt > 0.32 90% FCAL clusters from Zee sample and 2.1% from Dijet sample pass the cut.

EMEC FCAL

In release 13, all the used cluster moments are available in the AOD



With info from clusters at EMEC and FCAL …With info from clusters at EMEC and FCAL …

Theses results come from previous study using bugged dataset and id_bdt >0.4 for EMEC and FCAL•Bad linearity around 2.5% due to the 1mm bug•The resolution still needs a better EM calibration

For instance, for a 500 GeV graviton : We can reconstruct 10% more events in the >2.5 region keeping a good resolution and linearity :

The angular distribution in extreme fwd/bwd regions are able to be recovered …

…And the spin of the resonance is crucial to

understand what kind of physics we are dealing with.



There are some other topics that I have omitted:•Andre Asevedo Nepomuceno studied at Bremstrahlung Recovery but he has shown only Rel.11 results.•Reza Yoosoofmiya et al. looked at Charge Misidentification dilepton jets group •Vikas Bansal et al. studied alternative criteria to IsEm (likelihood, NN, …) dilepton jets group

Still to do :•Look at isolation criteria (inefficiency at high pT)•We have to chose identification cuts for electrons and photons•Look at Pileup ?

For the Electron / DiElectron :•Look at electron linearity and resolution versus E, pT.•Look at DiElectron efficiency versus mass for uubar and ddar separatly.•Look at the background rejection to choose the identification criteria

For the Photon / DiPhoton :•Look at the photon and DiPhoton resolution and linearity•Look closer at the background rejection



Backup slidesBackup slides





Results obtained for ZResults obtained for Zeeee

•The InvMass shift is probably due to the 1mm bug•The resolution is worse compared with two reconstructed electron events, which needs a better EM calibration•The number of interresting events become 708 instead of 500 by taking events with 1 EMLike cluster



Results obtain for ZResults obtain for Zee angular distributionee angular distribution

With info from clusters at EMEC and FCAL, angular distribution in extreme fwd/bwd regions are able to be recovered …

Difference between spin 1 and 2 is only sensitiveto extreme fwd/bwd regions.

Leptons with high pseudorapidity are important for the spin evaluation .

…And the spin of resonance is crucial to understand what kind of physics we are dealing with.



Kinematic distributionsKinematic distributions

pT, , and E distribution for gamma coming from 120 GeV Higgs

Generation

Reconstruction



Kinematic distributionsKinematic distributions

pT, , and E distribution for gamma coming from Diphoton events

Generation

Reconstruction

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Status of the studies on e/gamma ID, performance, and selection

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