University of Iowa

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University of Iowa
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Event generation and reconstruction
PYTHIA 6.2, CMSIM , ORCA version 7.6.0, Pileup
Signal events - qqH 300,350 and 500 GeV mass
Higgs were generated.
No tracker was simulated, e e- were selected
from generator particle information
Higgs and Z decay (forced) modes
Background considered in this analysis
All cross sections listed here are basically ??BR
decay chain
Analysis note submitted CMS AN 2005/014 In
stage of review Presented on HIGGS working group
meeting -- good response. Closely working with
referees.
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Pre selection cuts

• At least two tracks with opposite charge,
• which then can be Identified as
  electron/positron
• Soft cut on Pt of tracks gt 10 GeV

1) Iterative cone algorithm Cone radius
0.5 2) At the preselection stage as jet was
Accepted any object found by the jet
finder with Et gt 20 GeV 3) Jets are well
within CMS detector acceptance ? ? 5 4)
No calibration
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Some assumptions
VERY PRELIMINARY
Main assumption in this analysis is made on
the Electron identification and its
efficiency.
IT IS ASSUMED THAT ELECTRON IDENTIFICATION
EFFICIENCY WILL BE AT THE LEVEL OF 94 95
In a region between arrows Falls more than 90
of Electrons, provided selection Cuts are
applied on tracks
Assumption is based on Many different
sources. One of them DC04 data with full track
simulation MY STUDY
a) Well isolated two opposite charge
tracks b) Cut on Et of the tracks etc.
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Cuts for leptons and missing ET
Leptons (e e- ) were selected from generator
particles data. Lepton cuts ?lt2.4, ET
gt 20GeV, M(e e-)-M(Z)lt15GeV,
Leptons are between tag jets
Cut for reconstructed missing ET gt 50GeV
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FORVARD JET TAGGING Jets
selection
Forward jets were searched using rapidity gap
method Over all pseudo rapidity range.
Jets ET ? 30GeV reduces Pileup contamination
Jet pairs per event
Jet isolation criteria nothing around the
jet in cone 0.5 Jets must be in opposite
hemisphere ?1 . ?2 lt
0 Difference between jets Pseudorapidity
more than 4.0
If more than one combination of such jets found,
jets with largest rapidity difference were
accepted as a tagged jets
Majority of signal events has At lest one pair
of tagged jets
If no such combination was Found, event was
dropped
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FORVARD JET TAGGING Jets Et and
di jet mass
Di Jet mass distribution for Signal and
background events
E t of tagged jets
Cut is applied at 500 GeV
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Central Jet veto
Standard approach first to find tag jets, then
to veto events with additional central jets.
First veto events with central jets, than search
for tag jest
Pseudo rapidity range -2.0 lt?lt 2.0
Events with central jets were vetoed before
forward jet tagging
No need to use b tagging at all
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Signal Significance
Signal Significance for different ? range
BUT SIGNAL SIGNIFICANCE IS STILL WELL BELLOW THE
ACCEPTABLE 5? LEVEL
.
Even the background events Are suppressed
substantially, Small cross section for
signal Events and huge cross section For
background is main reason For such low
significance.
Significance is calculated For 60 fb1 LHC
integrated luminosity
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Significance extrapolation
Decays considered --- One Z decay to
electrons Second Z to any kind of neutrino
BUT Anyway below the 5? level For 60 fb1 LHC
integrated luminosity
Significance is calculated For 60 fb1 LHC
integrated luminosity
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Significance extrapolation
Taking into account Z decay to muons electrons
And neutrinos -- Very similar Analysis. High
efficiency For muon identification (?97)
according DAQ TDR
Significance is calculated For 60 fb1 LHC
integrated luminosity
Extrapolation gives 6 times More events
for signal, while background goes up by factor
2. Increase factor for significance is app. 4.26
Could be considered as An upper limit muon
Efficiency is not included
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SUMMARY