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MissingET reconstruction: From basic EtMiss to Refined Calibration

This workshop presentation discusses the roadmap for the validation of EtMiss in the context of ATLAS Hadronic Calibration. Topics covered include data quality, noise, dead channels, and the steps involved in the reconstruction of missing transverse energy.

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MissingET reconstruction: From basic EtMiss to Refined Calibration

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  1. MissingET reconstruction: From basic EtMiss to Refined Calibration ATLAS Hadronic Calibration Workshop2009 Foz do Arelho, Portugal S. Resconi

  2. Roadmap for Validation of ETmiss • Before Collisions: Data Quality • Noise • Dead channels • 2009 data: First collisions • From basic EtMiss: • Minbias • Dijets • to Refined EtMiss: • Use reco objects as soon as validated • Surprises in data: pile-up, tails • 2010 data: 10-100 pb-1 • Observables • Zee, Zmumu • Neutrinofication • Ztau tau • Wlnu • ttbar • MET Tails in SUSY (next talk)

  3. Sp=0 Spi=0 Transverse Missing Energy: EtMiss= ExMiss2+EyMiss2 ExMiss =-SEx EyMiss =-SEy SumET = SET pi p p Sum of energy of all particles seen in the detector p SEx e SEy EtMiss measurement in ATLAS EtMiss is event quantity • all detectors contribute • It is calculated from all significant signals • All calorimeter signals • Calorimeter signals in physics objects • Calorimeter signals not used in physics objects • Muons • Tracks in regions where calorimeter/muon spectrometer are inefficient • Correction for energy lost in dead materials

  4. MissingET reconstruction: step by step procedure Event Data Model and AlgTools structure provide high level of modularity: this allows to implement a step by step procedure of increasing complexity for the commissioning of the EtMiss  Event Data Model (MissingETEvent package):  EDM is made of simple and general classes that use enumerators to specialize data:  is suitable for MissingET data: basic unit is made of the 3-vector: (m_exMiss, m_eyMiss, m_etSum) but can have many different sources : calorimeters, muons, truth, DM regions…  permits to minimize the number of data classes  gives flexibility to the architecture,easy to be extended: to add a MET new object just add a new source, no EDM changes !  AlgTools structure and flow (MissingET package):  implementedtwo main Algorithms: METAlg and METRefAlg to handle two main approaches for EtMiss calculation and calibration:  Global Calibration (MET_Final) Refined Calibration (MET_RefFinal)  AlgTools configuration in /python/METGetter.py and METRefGetters.py  each AlgTool is responsible to create/fill and record in StoreGate one MET object  different levels of “descoping” for EtMiss reconstruction already tested in the reprocessings of the cosmics and single beam data during 08/09

  5. Basic EtMiss calculation • METCellMaskTool provides an interfaces to BadChanTools by LAr and Tile Calo that access channel quality and mask channels • LArBadChanTool/Masker, TileBadChanTool combined in CaloBadChanTool • See previous session: contribution by Behi “Large Scale MET Cosmic Study” (1) CaloCellContainer (2) CaloTopoClusters METtopoObjTool METCaloCellTool Cell Loop Loop on TC and backnavigate to TopoCells 2 noise cut METSelectorTool TopoCell CaloCell METCaloTool MET_Topo MET_Base METCellMaskTool MET_Topo_Mask MET_Base_Mask METCaloTool With the higher level of descoping very basic cell-based EtMiss Calculation applying two different noise suppressions: (1) from all Cells with |E|>2 noise (2) from all Cells inside TopoClusters  Provided also the possibility to mask bad channels  No calibration

  6. • Significant improvements in events with random triggers in cosmics in last year: improved bad-channel data base and masking of bad channels at calorimeter level improved energy reconstruction improved noise description SumET= scalar sum of Cell ET with |E|> 2 noise •  miss = atan(Ex miss/Ey miss)  should be gaussian centered to zero in random trigger evts ( expected)  improvements from 1° reprocessing to last reprocessing Basic EtMiss with random trigger E.Petit D. Varouchas METbase: from all Cells with |E|> 2 noise METtopo: from all Cells in TopoClusters  provides better perfomance !

  7. EtMiss Global Calibration (1) CaloCellContainer (2) CaloTopoClusters (3) CaloCalTopoClusters MET_TopoObj METtopoObjTool NO calib METCaloCellTool Cell Loop Loop on TC and backnavigate to TopoCells MET_LocHadTopoObj 2 noise cut METSelectorTool LocHad calib TopoCell CaloCell METCaloTool MET_Topo NO calib MET_Base NO calib MET_Calib MET_CorrTopo METCalibTool H1 calib H1 calib MET_LocHadTopo LocHad calib  Cell weights are applied for EtMiss Global Calibration: • H1-style calibration: • cell weights, depending on cell energy density E/V, on |h| and on calorimeter region, determined optimizing the jet resolution • LocalHadron calibration: • cell weights obtained using MC calibration hits info: energy deposition (active and inactive parts) in detector and dead material. • EtMiss from calibrated cells and from calibrated TopoClusters: similar results

  8. MET_CorrTopo MET_Final METFinalTool MET_MuonBoy MET_Cryo Final EtMiss reconstruction • To calculate the Final MET should be added also: • MET_Cryo = Correction for energy lost in cryostat between EM and Had calorimeters, Sum Ex and Ey cryostat correction from each jet: MET_MuonBoy = Muon term, calculated adding contribution from: • isolated muons: use combined tracks plus CaloMuons MuTag tracks to take into account also muons in crack regions respectively: |h| < 0.1, 1<|h| < 1.3 • To avoid energy double counting the muon energy deposited in calorimeter is not added in the Final MET calculation • non-isolated muons: using combined reconstructed muons but taking the momentum from the external muon spectrometer only • For first dataa more robust approach is forseen: no separation between isolated and non-isol, and use for ALL muons the combined reconstructed muons taking the momentum from the external muon spectrometer only (no problem of double counting in calos)

  9. < 1 pb-1 data: in-situ EtMiss validation with minbias evts • control sample to test EtMiss resolution up to SumET~200 GeV • no MC Truth needed to build the resolution curve  No MET expected in minbias events  (minbias) = 80 mb  Resolution curve done with 100k evts Final Ex(y)miss Resol = p0 *  SumET • METbase: from all Cells with |E|> 2 noise • METtopo: from all Cells inside TopoClusters  provides better perfomance !

  10. < 1 pb-1 data: in-situ EtMiss validation with QCD di-jet evts  control sample to test EtMiss resolution for SumET >200 GeV  J4 pt(jet)=140 – 280 GeV,  (j4) = 150 nb  Resolution curve done with 250k evts Final Ex(y)miss Resol = p0 *  SumET Reconstruction and calibration steps resolution improves from MET_Topo toMET_Final: MET_Topo  p0=0.56  no calibration applied MET_TopoCorr  p0=0.54 apply H1 calib MET_Final  p0=0.51 add cryostat correction MET_LocHadTopo_Final  p0=0.55  apply LocHad calib

  11. Refined EtMiss Calibration • implementation in Athena is based on an association map • between reconstructed objects and their constituent CaloCells and/or TopoClusters.  the association map allows to remove overlaps at cell level The set of METRefTools which access/fill the association map for each reconstructed object: METRefEleTool METRefTauTool METRefJetTool METRefMuoTool METRefCellOutTool METRefCellOutTool : loop on all CaloCells in TopoClusters not associated to any reco objects fill the association map with: *CaloCell, *TopoCl, CaloCell weight calculate METRef_CellOut Each RefTool : loop on identified Reco Objects collections for each Reco Obj backnavigate to its CaloCells fill the association map with: *CaloCell, *RecoObj, CaloCell weight calculate METRef_obj METRef_Ele METRef_ METRef_Tau METRef_BJet METRef_Jet METRef_Muo MET_CellOut + + + + + + + MET_MuonBoy + MET_Cryo = METRef_Final • cell weights depend on the type of the reconstructed object (e/, , b-jet, jet, m …) • particle identification driven by MissingET package jobOptions. •  each contribution is individually available in ESD/AOD, degrees of freedom in physics analysis

  12. Refined EtMiss Calibration • Electrons/photons (MET_RefEle, METRefGamma):  Default Calib = EM Scale RefCalib = CalibHits based e/g calibration  the different effects (sampling, material in front, longitudinal leakage, out of cone)are separately corrected • include corrections for sampling, material in front, longitudinal leakage, BUT NOT the out-of-cone to avoid double counting  will become the default after some more tests • Jets (MET_RefJet): Default Calib = H1-style, Other possibility = LocHad RefCalib = possibility to apply jet scale if out-of-cone correction is not included to avoid energy double counting • Taus (MET_Tau): Default Calib = H1-style,Other possibility = LocHad RefCalib =Use the best Tau calibration to improve mass reconstruction of tt final states (apply scale factor ? ) • Cells outside reco objects (MET_CellOut):  Default Calib = H1-style  Other possibilities = LocHad, MiniJet MiniJet = special calib for low pT depositions integrated in MissingET package from ObjMET: • build the MiniJet Collection (jet threshold=20 GeV) on the remaining TopoClusters not belonging to any reco object: • if the TopoCluster belongs to a MiniJet  weights depend to the  / classification of the MiniJet (sampling calibration) • if the TopoCluster does not belong to a MiniJet  weights depend on the CaloRegion of the TopoCluster (Barrel, Endcap, FCal) (region calibration)

  13. Resolution and Linearity for all reco STEPS Ztt D. Cavalli MET_Base |E Cell|> 2 noise,no calib MET_Topo Cells in TC, no calib MET_Calib  |E Cell|> 2 noise, H1 calib MET_CorrTopo Cells in TC, H1 calib MET_LocHadTopo p0=0.5  Cells in TC, LocHad  Added Muon term to all previous STEPS METFinal p0=0.49 METRefFinal p0= 0.48 |E Cell|> 2 noise Cells in TC Final Ex(y)miss Resol = p0 *  SumET No calib  Linearity is more sensitive to calibration !  below 20 GeV the reconstructed MET is expected to be larger then Truth LocHad gives best Linearity within 5% calib 5% Linearity = (TruthE T miss – RefFinal)/TruthE Tmiss

  14. Resolution and Linearity for all reco STEPS Wen D. Cavalli MET_Base |E Cell|> 2 noise,no calib MET_Topo Cells in TC, no calib MET_Calib  |E Cell|> 2 noise, H1 calib MET_CorrTopo Cells in TC, H1 calib MET_LocHadTopo p0=0.45  Cells in TC, LocHad  Added Muon term to all previous STEPS METFinal p0=0.5 METRefFinal p0= 0.44 |E Cell|> 2 noise Cells in TC Final Ex(y)miss Resol = p0 *  SumET • Linearity depends on topology  S-shape, jump at ~ 40 GeV •  for True MET  40 GeV RefEle term dominates • for True MET > 40 GeV RefEle,RefJet+CellOuthave similar Mean value  RefFinalandLocHadTopogive the best linearity within  5% No calib calib +5% -5% Linearity = (TruthE T miss – RefFinal)/TruthE Tmiss

  15. MET Linearity: Wen changing calibration for MET_RefEle Standard Calibration RefEle=Refined CalibHit(no out of cone) RefEle=EMScale +10% +10% +5% +5% -5% -5% -10% -10% Preliminar results: low statistics Linearity of response = (MET_Truth – MET_RefFinal)/ MET_Truth Linearity is within  5% for 20<True MET< 60 GeV for EMScale and Refined CalibHit • Below 20 GeV the reconstructed MET is expected to be larger then Truth •Above 60 GeV statical error too large Including the complete electron calibration spoils the linearity  double counting the out of cone energy !!! RefEle=Completeele calib (without of cone) +10% +5% -5% -10%

  16. TTbar BACK-UP SLIDES

  17. MissingET reconstruction on AOD • Request from physics:possibility to rerun quickly MET reconstruction changing calibration and/or particle identification. • New code is ready in rel 15.2.0: • Provides the possibility to rerun refined calibration on AOD • New design by P. Loch permits to use same METRefTool for ESD and AOD reco configuring themselves with processors according to cell or cluster use • Which constituents are used at AOD level ? • constituent TopoClusters of taus and jets (no more cell connection on AOD) • constituent CaloCells of electons/photons/muons (available on AOD) • How to apply overlap removal at AOD level ? • cannot use only TopoClusters because ele/photons/muons are not built on TopoClust • new method to associate CaloCells to TopoClusters:Calculate likelihood that a cell is within the Topocluster envelop around barycenter (see talk by Peter) •  What is missing at AOD level ? • calibration available at AOD level are: RefEle, EM Scale (for ele/photons) • LocHad  NO H1 (for jet/taus/cellout) •  to have all possible calibrations also at AOD level: • need to use all 3 signal states (H1, LocHad, EmScale) of TopoClusters •  still to test H1 signal state inside the MissingET

  18. MET reco on ESD (nightlies for rel 15.1.0) MET reco on AOD (nightlies for rel 15.1.0) validation of MissingET reconstruction on AOD mc08.106052.PythiaZtautau MET_RefEle MET_RefGamma MET_RefJet MET_CellOut • Some differences expected in AOD reco : • • Different calibrations for taus/jets/cellOut: • on ESD H1 applied at cell level • on AOD locHad at TopoCluster level • • MET_RefJet (include also taus) MET_RefFinal

  19. BACK-UP SLIDES

  20. PEMB EMB PEMEC EMEC TILE HEC FCAL (MET_BASE – MET_BASE_MASK) vs MET_BASE_MASK MET_BASE – MET_BASE_MASK 400 MET_BASE MET_TOPO 20 Masking of bad channels in MissingET Some results on single beam data: run 87764/physics_L1Calo/ with rel 14.5.0.5 • After masking all bad channels: •  big effect on smallMET and SUMET values •  few events particularly affected for MET > 20 GeV • Tile Calo gives the main contribution (probably needed a more refined classification of “affected” channels in Tile)  Masking of bad channels should be done at Calorimeter Cell level to provide coherent reconstruction of the entire event, but if needed possibility to mask only in MET reconstruction • Control plots in different subdetector regions

  21. MET Linearity changing calibration for MET_CellOut mc08.106020.PythiaWenu_1Lepton RefEle=Refined CalibHit (no out of cone) RefGamma= EMScale RefJet, RefTau=H1, CellOut=EM RefEle=Refined CalibHit(no out of cone) RefGamma= EMScale RefJet, RefTau, CellOut=H1 +10% +10% +5% +5% -5% -5% -10% -10% RefEle=Refined CalibHit (no out of cone) RefGamma= EMScale RefJet, RefTau=H1, CellOut=MiniJet RefEle=Refined CalibHit (no out of cone) RefGamma= EMScale RefJet, RefTau=H1, CellOut=LocHad +10% +10% +5% +5% -5% -5% -10% -10%

  22. Event Data Model (MissingETEvent) : Enums for Source of Signals: Calo, Calib, Truth, Muon, Final, Cryo, Topo, Ref, ObjElectron ObjMuon, ObjJet, ObjIdTrk, ObjMiniJet, ObjRest, ObjFinal Enums for  Regions: Central, EndCap, Forward Enums for Truth Source: Int = all int particles till abs(eta) <= 5 NonInt = non interacting particles IntCentral = int particles in abs(eta) <= 3.2 IntFwd = int parts in Forward region IntOutCover= int parts with abs(eta) > 5 Muons = truth muons ( all ) Enums for Calo Regions: PEMB, EMB , PEMEC , EMEC , TILE, HEC, FCAL

  23. MET Tails D. Cavalli From resolution plot: Tail = (Nevts in bins > Mean  3 s) / Nevts

  24. +5% MET Performance: Wen D. Cavalli True MET > 40 GeV True MET  40 GeV Resolution and Linearity for all MET reco STEPS: •Resolution= Final Ex(y)miss Resol = p0 *  SumET  METRefFinal p0= 0.44,MET_Final p0=0.5 MET_LocHadTopo p0 = 0.45 •Linearity = (MET_Truth – MET_RefFinal)/MET_Truth  depend on topology: S-shape, jump at ~ 40 GeV for True MET  40 GeV RefEle term dominates for True MET > 40 GeV RefEle,RefJet+CellOut similar Mean value  METRefFinal and MET_LocHadTopogive the best linearity within  5% MET_RefEle andRefJet+CellOut distributions -5%

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