Update
Karol Krizka and Michele Petteni
Simon Fraser University
CERN, 23/06/2009
Outline
Variable Definitions
Possible Backgrounds
Building Z → nunu Templates
Building Z → ll/W → lnu Templates
Karol and Michele (Simon Fraser University) Update 23/06/2009 2 / 28
Variable Definitons
→
− →
−
HT = PT + E T
TwoJets
−→
−− →
−
MHT = PT
TwoJets
−→ −
−− →
MET = ET
Note: For the vector variables, we plot the magnitude.
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Background Sources
Electroweak Background
Missing ET
Z → nunu
Unreconstructed Z → mumu and W → munu
Extra Jets and Missing ET
Z → ee
W → enu
QCD Backgrond
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Generator Level Cuts
Z → nunu has a generator level filter applied, so is inconsistent with the
other samples.
Filter:
Require at least one jet with
PT > 30 GeV
Eta 30GeV
Second Leading Jet ET > 30GeV
Third Leading Jet ET 100GeV
At least two reconstructed leptons (except Z → nunu)
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Missing ET
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Missing HT
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HT
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Building Z → ll / W → lnu Templates
Further assumptions:
There is no difference between reconstructed and non-reconstructed
Z’s.
There is no difference between non-reconstructed W’s and
reconstructed Z’s.
If these assumptions are true, we can combine all of the electroweak
background into one template.
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My Cuts
First Leading Jet ET > 30GeV
Second Leading Jet ET > 30GeV
Third Leading Jet ET 100GeV
No Reconstructed Leptons
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Background Cross Sections
Process Np0 Np1 Np2 Np3 Np4 Np5 Total
Z → nunu 0.000 1.318 18.291 8.461 2.042 0.305 30.42
Z → mumu 0.000 0.007 0.117 0.046 0.012 0.001 0.18
Z → ee 0.000 0.000 0.000 0.000 0.000 0.000 0.00
W → munu 0.003 0.546 6.639 2.941 0.719 0.106 10.95
W → enu 0.004 0.761 2.406 0.989 0.220 0.037 4.42
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Missing ET
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Missing HT
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HT
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Electron-Jet Contamination
It is possible that the electron in W → enu is detected as a jet, but not
reconstructed as an electron. This would drive missing ET down.
Solution:
Cut on the EM fraction of the two leading jets such that
0.1 < EM Fraction < 0.9
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W → enu Cut On EM Fraction, No MET Cut
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W → enu Cut On EM Fraction
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Detector Problems
It is possible that the difference between the reconstructed and
non-reconstructed plots could be due to kinematics that kept the leptons
from being reconstructed. For example, the muon chambers end at Eta of
about 2.6. Test:
Compare the truth ET of the reconstructed and non-reconstructed Z’s
Define a lepton as reconstructed if it lies within eta of 2.6
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Truth Z ET Distributions
Based on Monte Carlo
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Truth Z PT Distributions
Based on Monte Carlo
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Reconstructed Z → mumu Missing ET
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Detector Problems
The ET of the Z depends on eta and exhibits the same pattern as in
the reconstructed vs non-reconstructed missing ET plot
The PT of the Z depends on eta, but not as much as ET
We are currently modifying the missing ET of the event based on the
leptons’ ET . Maybe we should switch to PT ?
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Z → mumu Missing ET , Modified With Mu’s PT
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