Alexi Mestvirishvili

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Status of the qq ? qq h study
Alexi Mestvirishvili University of
Iowa Department Physics and Astronomy
Comments and question direct to
Alexi.Mestvirishvili_at_cern.ch
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• Events generation by PYTHIA 6.1.52
• Detector response simulation by CMSJET

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Signal events

• fi fj ? fi fj h
• (Higgs production via WW
  fusion)
• Higgs mass was chosen to be 300 GeV
• Higgs decay h ? ZZ
• Z decay Z(1)? ee- Z (2) ? ?
  ?
• Two forward jets are generated after
  the
• quarks from incoming protons radiates W
  s

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Background processes considered so far
2) WW ? ZZ 3) ZZ
Z(1)? ee- Z (2) ? ?
? 4) Zjet fi fi ?
Z0
f g ? f Z0 Z ?
ee- N number of
events in each set 100000
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Cross-sections and luminosities ( ? given by
PYTHIA)
Tab.1
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Jets selection
1) All
reconstructed jets must be well within CMS
aperture -5 lt
? lt 5 2) Forward jets selection
2.5 lt ? lt 5 3) Jet
transverse energy
Et gt 20GeV 4) At least one tagged forward jet
satisfying the criteria above
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leptons (ee- ) selection

• 1) Presence of two isolated lepton required
• (one electron, one
  positron)
• 2) ?(lepton) lt 2.4
• 3) Et (lepton) gt 20GeV
• 4) Invariant mass of two leptons must be in
  vicinity of Z mass --- M(ee-) M(Z) lt
  5GeV

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Jets multiplicity
Two jet events are dominant in the signal sample
N of jets
N of jets
NOT NORMALIZED
N of jets
N of jets
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Forward jet multiplicity
Most of the events has one forward jet in all
samples
N of jets
N of jets
NOT NORMALIZED
N of jets
N of jets
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Missing transverse energy E miss distribution
t
NOT NORMALIZED
Z jet events are almost completely killed by
the E miss cut
t
Emiss gt50GeV was required
t
Emiss (GeV)
t
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Efficiency
Tab.2
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Number of events
Nev ? ? L(lhc
year) where ? efficiency for
particular process L(lhc year) one year
LHC running integrated luminosity ?
particular process cross-section
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Number of events
Assuming one year running at low luminosity L
60fb-1
Assuming one year running at high luminosity L
100fb-1
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Bkg sources to be considered in near future

• t t Z
• Each t decays to W b with consecutive W decay to
  e?. Z decays to ee-.
• two neutrinos from W generates large missing
  transverse energy.
• Charged leptons
• A) two e from W are out of tracker
  acceptance, two e from Z are in
• one electron/positron from Z and one
  positron/electron from one of the W are in the
  tracker acceptance others out
• Jets
• C) both b jets from t decay are forward
  i.e. could not be tagged as a b jets.
• one b central, another forward and one forward
  jet is generated by ISR or FSR.
• both b jets central, two forward jets are
  generated by ISR or FSR

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Bkg sources to be considered in near future
A) C) worst case scenario, final
state configuration exactly as in signal
events. Significantly will
affect the signal to background ratio. A) D)
and A) E) b jet tagging will suppress this
kind of configuration, but
assuming b tagging efficiency
is expected to be 60-70
will contribute to the signal
to background ratio. B) C), B) D)
in addition to the b jet tagging needs to
investigate or
dilepton mass distribution, in order to
determine the B) E)
distribution exact shape to use side band
subtraction
method.
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Bkg sources to be considered in near future

• t t
• Each t decays to W b with consecutive W decay to
  e?. two neutrinos from W
• generates large missing transverse energy.
• Charged leptons stays central and they are
  detectable.
• Jets
• both b jets from t decay are forward i.e. could
  not be tagged as a b jets
• one b central, another forward and one forward
  jet is generated by ISR or FSR.
• both b jets central, two forward jets are
  generated by ISR or FSR
• Needs to investigate dilepton mass
  distribution, in order
• to determine the distribution exact shape
  to use side band subtraction method.