Searches for ZZ Diboson decays in 3 lepton channels

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Searches for ZZ Diboson decays in 3 lepton
channels

• Azeddine Kasmi
• Bob Kehoe

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OUTLINE

• A summary of December talk on ZZ ? 3e
• Attempts to locate the unfound electron using
  various algorithms
• Jets Algorithm
• Tau Algorithm
• Raw egamma
• Tracking Algorithm

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Signal and Background after Pt cuts ETmiss
Isolation
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Use Z mass as a cut
e2
Z

• Find which combination of 2 electrons makes a Z
  for both samples ZZ and Zbb (with opposite sign
  cut).
• Define a variable MZ_Best.
• Check the two combination M13 and M23
• The closest of them to the MZPDG is the
  MZ_Best.
• This Z_Best will be used to distinguish between
  ZZ and Zbb

e4

e3
e1
e1
Z
Z
e2
b
b
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Pt cut ETmiss lt 20 GeV Isolation
(etcone/et)on 3rd leading electron lt 0.1 MzPDG
MZBest lt 10 GeV

• Sig_eff 40
• (w/respect to the 671 (3e)
• That passed the Pt cuts)
• Bkg_rej 98
• Bkgsig 151
• helps a lot but want a better e

Try to find the 4th candidate electron to use it
to find the second Z peak
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The 4th Electron might be seen as a jet
In the event of 3 Medium electrons are
reconstructed With Pt gt 7 GeV and at least one
of them has Pt gt 20 GeV
Remove jets within dR lt 0.2 From any Medium
electron
ZZ sample
Does the jet candidate match The unfound
electron
Jet Candidate
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DR between Medium 3 electrons and jets
Most jets are electrons
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Jets vs Jet candidates in ZZ
Jets
Jet Candidates
Most events have at least 1 jet not matching a
medium electron
Looks like a Pt distribution of an electron from Z
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Jets and Jet candidate in Zbb sample
Jets in Zbb sample
Jet candidate in Zbb sample
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dR between a jet candidate and a truth electron
Most of jet candidate Match the unfound electron
There are 599 matches In dR lt 0.2

• e 599/671
• 89

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The Pt of unfound Electron(Left) in the jet
candidate(Middle) in the truth electron that do
not match the 3 medium
electron(Wright) its eta distribution
Wide range in eta coverage
Similar shapes
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Jet candidate eta and phi resolution
RMS 0.020
RMS 0.028
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Jet candidate Pt resolution in EMbarrel, EndCap
and FCAL
?
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In Tau Algorithm in ZZ sampleRemove jets within
dR lt 0.2From any Medium electron
Log
663 within dR lt 0.2
593 within dR lt 0.2
668 within dR lt 0.2
Most Taus are Medium electrons
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DR between a Tau candidate and the unfound
electron
In Tau Algorithm in ZZ sampleRemove jets within
dR lt 0.2From any Medium electron
Most Taus are Medium electrons
e 365/671 54
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Pt of the tau electron candidate
Eta coverage is narrower than it is jet algorithm
Similar shapes in that region
Pt threshold
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Eta, Phi and Pt resolutions in taus
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The 4th Electron might be an egamma object that
did not pass the electron ID cuts
In the event of 3 Medium electrons are
reconstructed With Pt gt 7 GeV and at least one
of them has Pt gt 20 GeV
Remove egamma objects within dR lt 0.2 From any
Medium electron
ZZ sample
Do the raw egamma match The unfound electron

Raw egamma objects
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DR between a raw egamma and the unfound truth
electron
e 409/671 60
Eta of raw egamma object that match the unfound
truth electron within dR lt 0.2
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Pt of a raw egamma object and the truth unfound
electron
Similar shapes
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Eta Phi and Pt resolution Resolution Raw egamma
candidate
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Pt of the track with no match in the egamma
cluster vs the unfound truth electron
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Summary table
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Conclusion and Future Plan

• Try to use the 4th electron efficiently to
  reduce the background.
• There is a variable in AANTuple of release 13
  which gives the EM fraction. This would be
  another tool to reduce the background.
• Optimization of the cuts

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Back up slides
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1st and 2nd leading jet candidate in ZZ sample
This 0 peak corresponds to events where there is
only ONE jets
This 0 peak corresponds to events where there is
not jets
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1st and 2nd leading jet candidate in Zbb sample