Electron Isolation in 22X
Adish Vartak
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Samples Used
• Drell Yan Sample
– /Zee/Summer08_IDEAL_V11_redigi_v2/GEN-SIM-RECO
• QCD Sample
– /QCDpt80/Summer08_IDEAL_V11_redigi_v1/GEN-SIMRECO
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Tracker Isolation
• Choice of Electrons
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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
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Quality Cuts on Tracks in Isolation
Cone
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Comparison With Muons
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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
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Profile of Tracks
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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.
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ECAL Isolation
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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
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50 GeV Electron Profile in the ECAL
Eta 0.1
Eta 1.3
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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’.
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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.
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