discovery potential of the sm higgs at the lhc
DESCRIPTION
Discovery Potential of the SM Higgs at the LHC. Junichi Tanaka ICEPP, University of Tokyo. Contents. LHC and ATLAS SM Higgs Production cross section and branching ratio VBF process Key issues Tau identification TauID performance Discovery potential with ~10/fb (~1 year run) - PowerPoint PPT PresentationTRANSCRIPT
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Discovery Potential ofthe SM Higgs at the LHC
Junichi TanakaICEPP, University of Tokyo
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Contents
LHC and ATLAS SM Higgs
Production cross section and branching ratio VBF process
Key issues Tau identification TauID performance
Discovery potential with ~10/fb (~1 year run) MSSM : Lighter Neutral Higgs Conclusions
CMS, Triggers, SUSY -> Roberto.C’s talk
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What is the LHC?
Proton-Proton (pp) Collider 14TeV
• 27km LHC tunnel• Installed in the existing LEP tunne
l
• 1232 superconducting dipoleswith B = 8.3 T working at 1.9 Kelvin
• Two general-purpose pp experimentsATLAS vs CMS
14m x 1232
image
Dipole magnet
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Geneva Airport
LHC tunnel (27km in circumference)( ~100m underground)
CERN
Swiss side
France sideJura Mountains
Large Hadron Collider
ATLAS CMS
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ProcessEvent rate at 2×1033
2007-8 L=10fb-1
Comparison(estimation at
2007)tt 1.6 Hz 107 104 Tevatron-2
bb: PT>10GeV200 KHz
(HLT 10Hz)2×1012
(108 inc. di-)109 Belle/BaBar
Higgs (130GeV)
200/h 5×105 ---------
SUSY (1TeV) 20/h 5×104 ---------
At the first year 2007~8 (L=10fb-1)
LHC is Top & B-factory.
LHC can be Higgs & SUSY factory!!!
Why is the LHC?
- Discovery of SM Higgs~ the last unobserved particle
- Discovery of New Physics
Measurement ofSM Higgs properties etc.
High energy High luminosity
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Time Schedule of LHC• April, 2007 : first beam, commissioning• September, 2007 : 7 months with L=2x1033 cm-2s-1 ” Low luminosity” r
un
Physics : L=10fb-1 -> Higgs/SUSY?
• 2007~2009 : Low luminosity run• ~2009 : L=1034 cm-2s-1 ”High luminosity” run
Sep. 11th, 2004ATLAS
ATLAS has started theinstallation of the detector.
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ATLAS (A Toroidal LHC ApparatuS)
• Inner tracking system : 2T solenoid magnet• Liq. Ar EM calorimeter• Muon spectrometer : air-core troidal magnet
E,P resolution (P ~ 100GeV) :
~ 2% e, ~ 1.5%Jets ~ 8%
•40MHz beam crossing•Readout channel = 160M channels•Raw data = 320Mbyte/sec (1TB/hour)
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SM Higgs Production at LHCGluon Fusion
Vector Boson Fusion (VBF)
Excluded by LEP
Associated WH, ZH
Associated ttH, bbH
VBF
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SM Higgs Decay
bb, , , WW, ZZare important at the lowmass region.
Observation of Higgs by multi modes
114.4 < mH < 193 GeV/c2 @95% C.L.
LEPEWWG Summer2003
Branching ratios
Can study Higgs properties in detail.
Couplings…
Difficult but interesting!
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Vector Boson Fusion Process
Characteristics High Pt jets in forward region Rapidity gap <- no color flow : no jet activitiesQCD background can be reduced by these features.
VBF H-> at low-mass region (mH = ~120GeV) Large production cross section and branching ratio Can reconstruct M(=mH) -> Can see a peak-> Discovery channel!!
Rapidity gap
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Branching ratio of H-> :• BR(lep-lep) = ~12%• BR(lep-had) = ~46%“Lep-had” mode plays an important role for the Higgs discovery.
MH =120GeV
h
4M Distributions of VBF H->
Hadronic tau decay mode
factor of ~4
(e only)
CMS
ATLAS
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Key Issues : Strategy for Discovery
For “VBF H->->lep,had” channel : More signals
Tau jet identification High efficiencies of tau jets with high rejection power of QCD jets
Less backgrounds Missing Et
Better resolution Make a tail of Z smaller Make a signal peak shaper
ATLAS
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Tau-jet identificationTau-jet = jet originated from hadronic tau decay We need to identify tau-jets from many QCD-jets.
Properties of tau-jet Hadronic decay modes of tau Narrowness Shower shape related with decay products (0,+-) of
Number of charged tracks
Next slide
Studying now
Most/Half of energy are deposited at EM.
Charged tracks : 1 or 3Photons from 0
Can be measured at InDet.
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Fraction of energy in R<0.1
20 < Pt < 30
40 < Pt < 5070 < Pt < 130Tau-jetsQCD-jets
R<0.4
R<0.1 ~90% of energy are depositedin R<0.1. -> narrow jet
ET(R<0.1)ET(R<0.4)
(transverse energy)
These distributions depend on luminosity due to the pile-up.
ATLAS, preliminary
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TauID Performance
No new result.-> studying …
ATLAS TDR 1999
We achieved eff=50% withRejection factor > ~100 forPt > ~40GeV.
We misidentify one QCD jetas a tau jet in ~100 QCD jets.
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Production Decay Mass region and purpose
Gluon FusionH -> 110-140GeV Mass
H -> ZZ-> 4 l 140-1000GeV Discovery, Mass, Spin, Coupling
H -> WW 130-170GeV Discovery
Vector BosonFusion
H -> 110-140GeV Discovery, Mass, Coupling
H -> WW 130-200GeV Discovery, W coupling
H -> 110-140GeV Discovery, Mass
H -> bb 110-140GeV Yb coupling
ttH
H -> bb 110-130GeV
Yt couplingH -> 110-130GeV
H -> WW 130-180GeV
WH H -> WW 140-170GeV Discovery, W coupling
Summary of SM Higgs StudiesATLAS
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Discovery potential of SM Higgs
Can discover Higgs withL=30fb-1 by >8(MH>114GeV:LEP limit)
MH < 200GeV:- Light case: VBF - Heavy case: VBF WW- Can observe Higgs
by multi-modes.
MH >200GeV:- H->ZZ->4lepton by >20
ATLAS
~5 with L=10fb-1
-> Discovery of Higgs within ~ 1 year
10fb-1
30fb-1
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Discovery potential of SM Higgs
CMS
10fb-1
30fb-1
60fb-1
~5 with L=10fb-1 -> Discovery of Higgs within ~ 1 year
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MSSM : Lighter Neutral Higgs
CMS
The lighter neutralhiggs h ~ SM Higgs
h mass increases withmA, tan, top mass,stop mass, stop mixing.
bbh coupling is enhanced stronglyat large tan.
h->, and bb+
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VBF process becomes important for the Higgs discovery in the low-mass region, mH=110~130GeV. Higher efficiency of tauID with a high purity is necessary to
discover Higgs as early as possible. We need to confirm our tauID using 10fb-1 of real data, Z->
. Study of missing Et is also important.
Conclusions SM Higgs can be discovered within 1 year ~ L=10fb-1
at both ATLAS and CMS.
LHC will start at 2007!-> SM Higgs!! and New Physics@TeV!!
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END
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CMS (Compact Muon Solenoid)
4T solenoid Compact muon spectrometer EM calorimeter PbWO4
Width: 21.5mDiameter: 15mWeight: 12500T