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Electron Isolation in

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					Electron Isolation in 22X

       Adish Vartak




                            1
             Samples Used

• Drell Yan Sample
  – /Zee/Summer08_IDEAL_V11_redigi_v2/GEN-SIM-RECO
• QCD Sample
  – /QCDpt80/Summer08_IDEAL_V11_redigi_v1/GEN-SIM-
    RECO




                                                     2
                Tracker Isolation

• Choice of Electrons
   •   Pt > 15.0 GeV
   •   Electron ID : Loose
   •   d0 w.r.t beam-spot < 0.2
   •   Number of hits in the tracker >= 11

• Isolation Cone
    Inner cone radius: 0.015
    Outer cone radius: 0.3


                                             3
Quality Cuts on Tracks in Isolation
              Cone




                                      4
5
Comparison With Muons




                        6
                   Gun Study
• FlatRandomPtGun used with single electrons
• 20.0 GeV < Electron Pt < 70.0 GeV
• Two samples considered
  – -1.479 < Electron η < 1.479 (Barrel)
  – 1.479 < Electron η < 2.5 (Endcap)
  – Entire φ coverage in both samples




                                               7
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Profile of Tracks




                    16
 Improvement in Endcap Performance
• Gun study indicates that a possible way to
  remove the signal tracks from the isolation
  cone is to put an eta strip veto similar to ECAL
  isolation.
• Eta strip of width 0.01 was tried.




                                                     17
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                ECAL Isolation
•   Noise cut in the barrel region: 0.08 GeV (2σ)
•   Noise in the endcap : 0.3 GeV (2σ)
•   Inner cone radius: 0.045 (Barrel)
•   Inner cone radius: 0.07 (Endcap)
•   Outer cone radius: 0.4
•   Eta Strip : 0.02
•   Isolation done using Rechits

                                                    19
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50 GeV Electron Profile in the ECAL




      Eta 0.1             Eta 1.3
                                    21
         Possible Improvement
• The eta strip acquires a bend as the absolute
  value of eta of the electron increases.
• Simplest model : Parabola
• Veto : |Δη – aηelΔφ2| < strip width (‘a’ is a
  parameter)
• A quick study gives an optimal value of 0.3 for
  the parameter ‘a’.


                                                22
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                   Results
• Small improvement in barrel, possible scope
  for further optimization
• Decrease in performance in the endcap !
• Another possible strategy to increase
  performance is to apply a leakage correction
  to the isolation value depending on the eta of
  the electron.
• However, preliminary attempts show no
  improvement.
                                                   25

				
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posted:7/20/2011
language:English
pages:25