HIGGS’ SELF COUPLING λ
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F. Duru, CMS HCAL Meeti ng, Fermilab 1 HIGGS’ SELF COUPLING λ F. Duru, M. H. Reno The University of Iowa
description
HIGGS’ SELF COUPLING λ. F. Duru, M. H. Reno. The University of Iowa. Higgs self-coupling. To understand the shape of the Higgs potential Higgs Potential: V H = - λ ν 2 ( Ф † Ф ) + λ ( Ф † Ф ) 2 where ν =((2) 1/2 G F ) -1/2 and Ф is the Higgs field - PowerPoint PPT Presentation
Transcript of HIGGS’ SELF COUPLING λ
F. Duru, CMS HCAL Meeting, Fermilab
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HIGGS’ SELF COUPLING λ
F. Duru, M. H. Reno
The University of Iowa
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Higgs self-coupling
• To understand the shape of the Higgs potential
• Higgs Potential:
VH = -λν2(Ф†Ф) + λ (Ф†Ф)2
where ν =((2)1/2 GF)-1/2 and Ф is the Higgs field
• λ = λSM= mH2/2ν2 λ is per se a free parameter
• The strength of λ affects the production rate of Higgs pairs in SM.
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SM Channel: g g HH
• Dominant Higgs pair production mechanism : gluon-gluon fusion
“Our” signal channel:g g HHW+W-W+W-(l± v j j) (l± v j j)
150 GeV < mH < 200 GeV (So far, mH = 180 GeV)
mH > 140 GeV H W+ W-mH < 140GeV H
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“The Code”
• Code (U. Baur’s) we use to generate events is a Fortran 90 and Fortran 77 combination
• CTEQ4 PDFs were replaced by CTEQ6 PDFs
αS= 0.118 CTEQ6L is the set used.
• Variables were changed to CMS Software variable format
• Ntuples are about to be ready
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Generated Event Plots
Higgs’ masses were set at 180 GeV
Plots are consistent with the set value.
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Generator Level W’s
Reconstructed W masses from generator information: Peaks around 80 GeV.
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Generated Higgs Bosons
Differential cross section vs Higgs boson’s Pt. Mean at 112.7 GeV.
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Pt & m
Mean: 310.1 GeV Mean: 381.3 GeV
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Rjl max, Rjj max, Rjl min, Rjj min
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Pt j max, Pt j min, Pt miss
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Backgrounds
Largest contribution:
W± W+ W- j j
Other backgrounds:
W W j j j j
W Z j j j j
1 top quark decays leptonically, the other one hadronically
W+ b W- b- j where 1 b quark decays semileptonically
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Background cross sections (fb)
For 180 GeV mH, √s = 14 TeV:
HH : 0.18
W± W+ W- j j : 0.40
: 0.22
: 0.08 : 0.05
: 0.002 W W j j j j : 0.005
U. Baur et al. (2002)
W Z j j j j : 0.15
Pileup ~ 0.03
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Backgrounds
• All the background channels are being produced with Alpgen
Cuts: pT(j) > 15 GeV pT(l) > 15 GeV
dR(jj) > 0.6 dR(ll) > 0.2
| η | < 3.0
• Interfaced with cmkin
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WWWjj W+ Plots
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W- plots
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MET
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Future plans
• These events will be put in CMS detector software: OSCAR + ORCA
• We will apply necessary cuts: PT, ΔR, η …
• mvis is an important value to distinguish the signal and background channels (value is much smaller for the signal).
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Future plans (cont.)
• Use χ2 test to obtain quantitative bounds on the Higgs boson self-coupling
• Plotting ΔλHHH [(λ-λSM)/ λSM] versus different Higgs boson masses will make possible to see upper and lower limits.
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λ bound
