QCD%20Background

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QCD Background and the Resolution

• Saminder Dhaliwal
• August 30th 2005

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Resolution!!!!

• Z -gt e- e aods
• Herwig and Jimmy
• Resolution as a function of Energy
• Resolution as a function of eta

• Formula (Reconstructed E True E) /
  (0.1)(sqrt True E)

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Resolution at different Energys
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RMS and Sigma
Full range of E 40GeV lt E lt 70GeV 50GeV lt E lt 70GeV 70GeV lt E lt 150GeV E gt 150GeV
Entries 35376 1684 1776 3056 1612
RMS 4.349 2.195 2.901 5.616 5.403
sigma 1.342 1.118 1.216 1.83 1.565
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Resolution at different etas
-2.5 lt eta lt -2.0
-2.0 lt eta lt -1.5
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-1.5 lt eta lt -1.0
-1.0 lt eta lt -0.5
-0.5 lt eta lt 0.0
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0.0 lt eta lt 0.5
0.5 lt eta lt 1.0
1.0 lt eta lt 1.5
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Resolution at different etas
2.0 lt eta lt 2.5
1.5 lt eta lt 2.0
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RMS (Black) and Sigma (Red) at eta
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QCD background Full Production
Begin by Filtering events to have a background
with a Lead jet and Second jet with certain Pt
requirements. As well as this we filter for a
possible Taujet and electron.

• Background mimics Higgs -gt TauTau signal
• Two tag Jets
• One Tau Jet and one electron

Higgs
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Filters 50 000 events generated with each filter
Filter Off 90
Filter 1 Filter 2 Filter 3 Filter 4
Lead Jet Pt 40 30 40 30
Second Jet Pt 20 15 20 15
eta gap 3.5 3.5 3.0 3.0
Number of Electrons 4 9 8 13
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Electron Pt with and without filter
Lead Jet Pt gt 30GeV Second Jet Pt gt 15GeV eta
gap gt 3.0
No Filter used
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Jet Pt with and without filter
Jet 2
Jet 1
Jet 3
Jet 4
Black Filter OFF Green Hard Filter (ON)
Red Soft Filter (ON)
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Jet Eta with and without filter
Jet 1
Jet 2
Jet 3
Jet 4
Black Filter OFF
Red Filter ON
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Delta Eta
Black Filter OFF
Red Filter ON
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Full Production

• Filter that asks for Lead Jet Pt gt 30GeV, Second
  Jet Pt gt 15GeV and eta gap gt 3.0
• We have at least 10 000 events with filters
  generated daily (about 5 of events pass filter).
  About 40GB/day
• Expect about 52 electrons of which 4-5 have
  Ptgt20GeV to be generated daily.

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Results so far

• Identifying electrons
• hasTrack and Pt gt 20GeV
• egamma
• isEM
• Minimizing background electrons, (while keeping
  optimum signal)
• Isolation cut (etcone)
• E/P restrictions

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Identifying Electrons

• HasTrack
• Cluster matched to track by
• 1) eta and phi at origin of track are compared to
  eta and phi of cluster. Need 0.05 agreement in
  eta, 0.1 in phi and E/P lt 4
• 2) Track extrapolated from cluster to origin, at
  each compartment deltaEta and deltaPhi are
  calculated. Required to be 0,025 and 0.05
  respectively.
• Egamma
• Differentiates between egamma object and soft
  electrons
• Considers shape of cluster and requires certain
  energy thresholds

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Identifying Electrons

• isEM
• A selection tool that considers the following
• ClusterEtaRange, ClusterHadronicLeakage,
  ClusterMiddleSampling, ClusterFirstSampling, Track
  EtaRange,TrackHitsA0, TrackMatchAndEoP, TrackTRT
  (not used now)
• Stricter than egamma, looks closer at the shower
  shape and track to calorimeter tracking.

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Identifying electrons Pt
hasTrack and Pt lt 20GeV
egamma
isEM
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Identifying electrons eta
hasTrack and Pt lt 20GeV
egamma
isEM
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Identifying Electrons
No Cuts hasTrack Pt gt 20 GeV egamma isEM
Number of electrons candidates 1.93646e06 129223 20372 264
of original candidates 6.67317 1.05202 0.0136332
Number of e- matched to Truth 1.25796e06 109705 17025 232
Fake Rate 53.9358 17.7913 19.6593 13.7931
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Minimizing Background electrons
etcone cut
etcone and E/P cut

• First Reduction by Etcone lt 10GeV
• Secondly 1.8 lt E/P lt 1.4
• Cut selection minimizes background whilst keeping
  signal efficiency as high as possible.

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Minimizing Background
hasTrack Pt gt 20GeV egamma isEM etcone lt 10GeV etconelt10GeV 1.8 lt E/P lt 1.4
Number of electron candidates 129223 20372 264 91 39
of original candidates 6.67317 1.05202 0.0136332 0.00469931 0.00201399
Number of e- matched to Truth 109705 17025 232 79 35
Fake Rate 17.7913 19.6593 13.7931 15.1899 11.4286