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

19 July 2007. Status of the studies on e/gamma ID, performance, and selection. Julien MOREL Exotic meeting. Outline. Electron and DiElectron identification and performance Z’  ee at 1 TeV Photon identification and performance G  gg at 500 GeV

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

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  1. 19 July 2007 Status of the studies on e/gamma ID, performance, and selection Julien MOREL Exotic meeting

  2. Outline • Electron and DiElectron identification and performance • Z’eeat 1 TeV • Photon identification and performance • Gggat 500 GeV • EM cluster identification at very high h • Conclusion and outlook

  3. Electrons and diElectrons

  4. Dataset and Athena version • Athena version : 12.0.6 • Process : Z’e+e-at 1TeV (Mll > 500 GeV) • Data Set : Correction of the 1mm bug have been applied • trig1_misal1_csc11.005605.Zprime_ee_pythia_chi1000.merge.AOD.v12000604_tid010014._00001.pool.root.2 • trig1_misal1_csc11.005605.Zprime_ee_pythia_chi1000.merge.AOD.v12000604_tid010014._00002.pool.root.3 • trig1_misal1_csc11.005605.Zprime_ee_pythia_chi1000.merge.AOD.v12000604_tid010014._00004.pool.root.3 • trig1_misal1_csc11.005605.Zprime_ee_pythia_chi1000.merge.AOD.v12000604_tid010014._00005.pool.root.2 • Number of events : 7250 Z’ee • We use electrons coming from the Z’ matched with the truth • Cross section = 376.5 fb

  5. Basic kinematics plots Cut at 500 GeV Due to Z’ Pic at 1 TeV Due to Z’ Pic at 1 TeV

  6. Electron 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 ==0 Medium : IsEM & 0x3FF ==0 Tight : IsEM ==0 Efficiency Efficiency Crack 1.4 – 1.5 Average efficiency of 95% for loose electrons and around 80% for medium electrons

  7. Electron selection criteria and efficiency Results for tight electron : splitting the different bit of IsEm up to IsEm == 0 Identification based on TRT and E/P are the main sources of loss. E/P loss increase with pT Average efficiency around 60% after isolation cut for tight electrons

  8. Electron resolution and linearity We can compute the resolution and linearity for the selected electrons : 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) Central Crack End-Cap

  9. The “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.

  10. DiElectron pairs selection criteria and efficiency • Dielectron pairs selection cuts : • 2 gene elec with |h|<2.5 • 2 reco elec • 2 reco elec with opp ch • IsEM Medium Average eff ~40% Loose Tight Average eff ~20% Average eff ~50%

  11. DiElectron mass resolution and linearity Barrel -Barrel Crak -Crak Barrel - EndCap Resolution = (0.82 ± 0.02) % Linearity = (0.07 ± 0.02) % Resolution = (0.84 ± 0.03) % Linearity = (0.15 ± 0.04) % Tight electrons 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)

  12. Photons

  13. Dataset and Athena (Kamile Dindar, Bob Kehoe and Haleh Hadavand) • Athenaversion : 12.0.6 • HighPtView-00-00-30 • Process : • Ggg(500 GeV) 4500 events • Data Set: • trig1_misal1_mc12.005623.Ggammagamma_500_pythia.recon.AOD.v12000601_tid006263 • trig1_misal1_csc11.005310.PythiaH120gamgam.recon.AOD.v12000502_tid005427

  14. HighPTView - 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.

  15. Photon kinematic distributions pT, h, j and E distribution for gamma coming from 500 GeV Graviton Generation Reconstruction

  16. Photon selection efficiency for photon coming from 500 GeV Graviton isolation on with ID cuts Drop at high pT Central Mean = 0.884±0.003 isolation off no ID cuts Central g pT (GeV) Mean = 0.902±0.003 isolation on with ID cuts Drop at high pT End-cap Mean = 0.652±0.005 isolation off no ID cuts End-cap g pT (GeV) Mean = 0.786±0.004

  17. EM clusters at high h

  18. Dataset and Athena version • Athenaversion : 12.0.6 • Data Set : • Process: 5144 Zee Ze+e- • BackGround :5802 JF17 Filter Dijet • Number 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 = Large h region : • EMEC : 2.5 < h < 3.2 • FCAL : 3.2 < h < 5.0 • Selection of topocluster with |h|>2.5 and 20GeV<Et<60GeV from CaloCalTopoCluster (Ning Zhou and John Parsons)

  19. Goal of the study In ATLAS, only |h| < 2.5 range is fully reconstructed as egamma objects. However, out of it, electrons could be approximated by EMlike clusters. TopoCluster compared with matched Truth Z decay electron There is a reco energy bias for EMlike clusters in FCAL : Et shift ~ 15% The goal of the study is to find a way to identify EMlike Cluster in order to reconstruct events with very large h electron (h>2.5). The large QCD background imposes a powerful method to identify EMlike Cluster.

  20. EM 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) EMEC FCAL 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. In release 13, all the used cluster moments are available in the AOD

  21. With info from clusters at EMEC and FCAL … For instance, for a 500 GeV graviton : We can reconstruct 10% more events in the h >2.5 region keeping a good resolution and linearity : • 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 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.

  22. 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

  23. Backup slides

  24. Results obtained for Zee • 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

  25. Results obtain for Zee angular distribution Difference between spin 1 and 2 is only sensitive to extreme fwd/bwd regions. Leptons with high pseudorapidity are important for the spin evaluation . With info from clusters at EMEC and FCAL, angular distribution in extreme fwd/bwd regions are able to be recovered … …And the spin of resonance is crucial to understand what kind of physics we are dealing with.

  26. Kinematic distributions pT, h, j and E distribution for gamma coming from 120 GeV Higgs Generation Reconstruction

  27. Kinematic distributions pT, h, j and E distribution for gamma coming from Diphoton events Generation Reconstruction

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