observing heavy higgs in weak boson fusion with forward jet tagging at the cern cms experiment
DESCRIPTION
Observing Heavy Higgs in Weak Boson Fusion with Forward Jet Tagging at the CERN CMS Experiment. HATICE DURAN YILDIZ DUMLUPINAR UNIVERSITY TURKEY. LHC, PRAHA CONFERENCE JULY 6-12, 2003. Outline. Standard Model & Higgs Mechanism Higgs Observation LHC-CMS experiment Weak Boson Fusion (WBF) - PowerPoint PPT PresentationTRANSCRIPT
Observing Heavy Higgs in Weak Boson Fusion with Forward Jet Tagging at the
CERN CMS Experiment
HATICE DURAN YILDIZ
DUMLUPINAR UNIVERSITY
TURKEY
LHC, PRAHA CONFERENCE JULY 6-12, 2003
Outline Standard Model & Higgs Mechanism Higgs Observation LHC-CMS experiment Weak Boson Fusion (WBF) Analysis of qqqqH, HWWljj qqqqH, HZZlljj qqqqH, HZZll Results
mH300 GeV
Limits of the Higgs Mass :• The mass of the Higgs boson is a free parameter because
of the unknown coupling λ, but• SM gives us information about the allowed mass range, by choosing
2Hm)( & finite &
Theoretical constraints & experimental limits :TeVmH 1 : unitarity purpose
Above this value, perturbation theory is not valid.
• Another hint for the mass of the H boson comes from the precision fits to electroweak observables : GeVmGeV H 21298
• Direct experimental search at LEP2 gives the lower bound on Higgs mass as : .1.114 GeVmH
gg fusion WW/ZZ fusion
associated Httassociated WH, ZH
BR
Characteristics of WBF
Forward Jets
Centrally produced Leptons
Color coherence between forward quarks
q
q
HW
W
W
l
q
q
W
qqqqH, HWWljj
# Events are generated with PYTHIA (6152).
# Calorimeter simulation, jet and ETmiss reconstruction
with CMSJET
# Jet reconstructions cone size = 0.5 for mH=600 GeV
= 0.7 for mH=300 GeV
# For pile-up:
--> 2 min. bias events superimposed at low luminosity
# We assume 90% efficiency to account for lepton reconstruction and trigger
Simulation of Events
I have looked the final states ofOne isolated lepton
Two central jets from W & ZOne forward jet + one backward jet
Main Backgrounds fromtt events
W + jets eventsZ + jets events
We show our results;For low luminosity only
For low (300 GeV) and for high mass (600 GeV) HIGGS
mH = 200 & 800 GeV studied too
How to isolate Higgs events?Signature, mass peakFind two vector bosons in event as H WW, ZZWl and Z Z llZ jj and W jjReconstructed Higgs WW or ZZ system
Exploit special Kinematics Pt(WW,ZZ) Pt(W,Z) Pt(l)Angular cuts
Higgs Production ModeWeak Boson Fusion: Tagging jets with very high mass
SELECTION CUTS:One isolated leptonNo charged track with pt>2 GeV in a cone R<0.3 around the lepton
pTl >30 GeV
Reconstruction of Leptonic W:
Pl is resolved from mW constraint
The smaller of the two solutions is selected
ETmiss >60 GeV
for 600 GeV & nocut for 300 GeV
PTWl>200 GeV for 600 GeV & no cut for mH=300 GeV
GeVEwith jetT 302
)1( jetjjW
Central jet cuts: No extra jet in
Top mass veto cut: Reconstruct top mass from 3 central jets
cut on
GeVmtop 220120
Etjets > 40
Reconstruction of Hadronic W for 600 GeV
Start asking 2 jets, ET > 40 GeV for Wjj and reconstruct mjj
No mass reconstructed since only 1j found (36%)
Reconstr. W mass in thecalorimeter for events with
1 central j & for events inthe tail mjj > 100 GeV.
Start from the directionof harder jet (or single jet), add cells in a cone R=0.9
Large tail dueto merging jets
W Reconstruction of hadronic W for mH=300 GeVTwo central jets with jet< 2
ETjet> 40 GeV
Problem of merged jets not too serious for mH=300 GeV.
Mass window cut65 < mjj < 100
Cut on PTW Hadronic >200 for mH=600 GeV
>100 for mH=300 GeV
PtHiggs
> 40 GeV
jjlWWH
S + B
Signal
Forward Jet Tagging
One forward & one backward jet with
2.0<jet<5
ETjet>20 GeV
For mH=600 GeV
Forward jet selection for mH=300 GeVForw. jet: Take the most energetic jet with >0 not in Wjj
Back. jet: Take the most energetic jet with >0 not in Wjj
Cut in | forw-back|>5
Cut in
|forw-back|>5
signal
W+jetstt
Forward jet energies for signal and backgrounds
How Big!!
300 GeV 600 GeV
Signal 25.3% 23.9%
tt 1.13% 1.6%
W + Jets 0.38% 0.6%
Efficiency for forward jet tagging
GeVE jetforw 300.
cutAsymGeVEGeVE jT
jT .50,30 21
TeVm jj 11. jetforwl
jjjj ,
Tagging cuts:
We have also tried
Event Selection for HWWlvjj for mH=300 GeV
Tagging jet
reductions
Com
pare
?
X 1000
Event Selection for HWWlvjj for mH=600 GeV
X 100
Com
pare
?
Event Selection for HZZlljj for mH=300 GeV
Event Selection for HZZlljj for mH=600 GeV
jjlWWH
mH=300 GeV
jjlWWH
jjlWWH
llZ
Same selection criterion used for Zlljj except Zll
lljjZZH
jjZ
lljjZZH
S+B
lljjZZH
Signal + backgro
und
GeVmforllZZH H 600
Channel mH=300GeV mH=600GeV mH=800GeV mH=200GeV
HWWllvj 10.3 7.8 6.2 3.9HZZlljj 7.8 8.5 6.3HZZllvv 3.6 5.5 3.2
Expected luminosities in fb-1 for 5 discovery
S / For an integrated luminosity of 30 fb-1B
Channel mH=300 GeV mH=600 GeV mH=800 GeV
HWWllvj 7.1 12.3 19.5
HZZlljj 12.3 10.4 18.9
HZZllvv 57.8 24.8 73.2
Channel Signal tt W/Z+jets
HWW l lvj x BR=0.015 pb
53 20 53
HZZ l ljj x BR=0.005 pb
16 6.2
HZZ l lvv x BR=0.0009 pb
6.4 4.1
Signal and background for H WW / ZZ with
mH=800 GeV
CONCLUSIONSIf Higgs Boson exists; HWWlvjj
HZZlljj
Channels via Weak Boson Fusion mechanism are potential Discovery channels at CMS experiment at CERN, LHC accelerator.
In 1 year of LHC running, CMS experiment would manifest with mass 300-800 GeV in WBF.
The analysis,HWWllvj for mH=200 GeV is still statistically acceptable.
Channel is MSSM is hopeless to observe any Higgs signal.