University of Iowa

1
University of Iowa
2
Higgs production and decay
qqH has second largest cross section
Final state topology two forward jets
Second largest Br for heavy H decay to ZZ
3
Event generation and reconstruction
Signal events - qqH 300,350 and 500 GeV mass
Higgs were generated.
PYTHIA 6.2, CMSIM , ORCA version 7.6.0, Pileup
Higgs and Z decay (forced) modes
H Z Z ee-??
WW fusion
ZZ fusion
WBF total
Background considered in this analysis
Has to be increased
4
Electron identification, issues Cuts for leptons
missing ET and jets
Since No tracker was simulated electron
identification efficiencies were derived from
the DAQ TDR numbers. Rate of Z? ee after L1 and
HLT and for low luminosity 1Hz, Derived
efficiency 0.26 correction factor for
background using L1 and HLT efficiencies for
ttbar 0.44
Leptons (e e- ) were selected from generator
particles data. Lepton cuts ET gt 20GeV
for background M(e e-)-M(Z)lt15GeV,
Leptons are between tag jets
Jet preselection
1) Iterative cone algorithm Cone radius
0.5 with Et gt 20 GeV 2) Jets are well
within CMS detector acceptance ??5
Cut for reconstructed missing ET gt 50GeV
5
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
6
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
7
Central Jet veto
Standard approach first to find tag jets,
then to veto events with additional central jets.
one of the jet is in central region (?1
-1) another in forward region (?2 3.5)
and satisfies tagging jet selection criteria
anti b-tagging is necessary to reject the
background events
First veto events with central jets, than search
for tag jest
Central region definition
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
8
Central Jet veto Acceptances
Overall acceptances when Forward Jet were Tagged,
then additional Central Jets were Vetoed (second
row) and with this cuts reversed (third row)
.
More than factor 3 is achieved in background
reduction by reversing of this cuts
Not corrected for electron identification
efficiencies
9
Acceptance and
significance
For 60 fb1 LHC integrated luminosity
Significance calculated using formula from
reference Expected signal observability at
future experiments V. Bartsch, G. Quast. CMS
note 2005/004
10
Significance
SIGNAL SIGNIFICANCE 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
11
SUMMARY