ATLAS Sensitivity to ATLAS Sensitivity to Standard Model and Standard Model and SUSY Higgs Bosons SUSY Higgs Bosons Stathes Paganis Stathes Paganis University of Sheffield University of Sheffield On Behalf of the ATLAS On Behalf of the ATLAS Collaboration Collaboration SUSY05, 19-July-2005, Durham UK SUSY05, 19-July-2005, Durham UK
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ATLAS Sensitivity to Standard Model and SUSY Higgs Bosons
ATLAS Sensitivity to Standard Model and SUSY Higgs Bosons. Stathes Paganis University of Sheffield On Behalf of the ATLAS Collaboration SUSY05, 19-July-2005, Durham UK. Outline. Discovery potential for Standard Model Higgs boson Higgs boson properties - PowerPoint PPT Presentation
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ATLAS Sensitivity to ATLAS Sensitivity to Standard Model and Standard Model and SUSY Higgs Bosons SUSY Higgs Bosons
Stathes Paganis Stathes Paganis University of SheffieldUniversity of SheffieldOn Behalf of the ATLAS On Behalf of the ATLAS
CollaborationCollaboration
SUSY05, 19-July-2005, Durham UKSUSY05, 19-July-2005, Durham UK
19-July-2005 ATLAS Sensitivity to SM and SUSY Higgs
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OutlineOutline
Discovery potential for Standard Model Discovery potential for Standard Model Higgs bosonHiggs boson
Higgs boson propertiesHiggs boson properties
Discovery potential for MSSM Higgs Discovery potential for MSSM Higgs bosonsbosons
19-July-2005 ATLAS Sensitivity to SM and SUSY Higgs
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ATLAS @ LHCATLAS @ LHC
Inner Tracker
EM Calorimeter
Hadronic Calorimeter
Muon Detectors
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SM Higgs: SM Higgs: ATLAS Discovery PotentialATLAS Discovery Potential
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SM Higgs xsections and branching SM Higgs xsections and branching ratios ratios
BR
bb
WWZZ
LEP excluded
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SM Higgs Discovery Potential SM Higgs Discovery Potential (Review)(Review)
2004High mass: MH > 180GeVH->ZZ->4lepton Has a narrow peak on top of a low background (pp->ZZ)
H -> 2photon- EMCalorimeter response uniformity to ~1% is required.
ttH -> WW bb -> blv bjj bb- b-tagging for all 4 b-jets to reduce combinatorics.
qqH -> qq- Forward jet-tagging needed.- Central jet-veto to reduce background.
Common:- Good knowledge of the background 1-10%.- All require low threshold triggers.
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130GeV Higgs: first year (10fb130GeV Higgs: first year (10fb-1-1))
Total S/ B : ~ 6
complete detector
• H->4l small signal but small background• 3/4 channels with less than 3• qqH->qqWW counting channel (no clear
peak); relies on knowledge of background
H->H-> H->4lH->4l qqH->qqH->
qqWWqqWWqqH->qqH->
qqqqSS 120120 55 1818 ~8~8
BB 25002500 <1<1 1515 ~6~6
S/BS/B 0.050.05 ~1~1
S/√BS/√B 2.42.4 2.82.8 3.93.9 2.62.6
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SM Higgs SummarySM Higgs Summary
For MFor MHH>180GeV, discovery should come >180GeV, discovery should come quickly mainly due to the H->4leptonquickly mainly due to the H->4lepton
For MFor MHH<180GeV a few tens of fb-1 will be <180GeV a few tens of fb-1 will be needed (a few years of low luminosity needed (a few years of low luminosity running)running)
The region around the LEP limit (115GeV) is the most challenging
All channels present experimental All channels present experimental challenges:challenges:
Uniformity/Linearity/Calibration of the calorimeters Missing-Et reconstruction b-tagging EM isolation, e/mu efficiencies, tau-ID, ...
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Higgs PropertiesHiggs Properties
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Higgs PropertiesHiggs Properties
Higgs MassHiggs Mass Expect ~0.1% accuracy using H->ZZ->4leptons
300fb-1 and H-> for MH<400GeV (ATLAS+CMS)
Higgs JHiggs JCPCP
Spin from H->ZZ and H->WW. Parity sensitive to angular correlations in H->ZZ-
>4lepton. Needs full luminosity.
Higgs CouplingsHiggs Couplings Only ratios of couplings (or partial widths) are
measured in a fairly model independent way. Absolute coupling determination requires further
theoretical assumptions. Needs full luminosity.
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Coupling Ratio Coupling Ratio determinationdetermination
A single JCP=0++ Higgs
Assumptions
No extra particles in loops,Only SM particles coupleto Higgs boson
Experimental and theoretical uncertainties for signal and background
Taken into account
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Absolute couplings after Absolute couplings after assumptionsassumptions
Assumptions:
Upper limit for either a coupling or a total width is required. The couplings to W,Z are not stronger than in the SM ( true for any n-Higgs Doublet Model )
Duehrssen et al hep-ph/0407190
Channels considered:
H->ZZ(*)->4lH->H->WW->ll+Et,miss
H->ttH, H->bb
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MSSM Higgs MSSM Higgs
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MSSMMinimal Supersymmetric extension: two Higgs doublets 8 degrees of freedom (5 particles):
CP-even : h,H CP-odd: A Charged: H+,H-
gu gd gV
h cos/sin -sin/cos sin(-)
H sin/sin cos/cos cos(-)
A 1/tan tan 0
Couplings to SM particles modified w.r.t. SM.
19-July-2005 ATLAS Sensitivity to SM and SUSY Higgs
19-July-2005 ATLAS Sensitivity to SM and SUSY Higgs
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Not just science fiction ...Not just science fiction ...
First Cosmic rays observed by theATLAS Tile calorimeter in the underground cavern in mid-June
Huge effort from ATLAS physicists to understand the detector (calibration, alignment, etc)
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SummarySummary SM Higgs should be discovered with a few SM Higgs should be discovered with a few
tens of fbtens of fb-1-1 over the full mass range. over the full mass range.
Higgs coupling measurement will require Higgs coupling measurement will require full luminosity. Accuracies of 15-50% are full luminosity. Accuracies of 15-50% are expected depending on the channel.expected depending on the channel.
At least one of the MSSM h or H should be At least one of the MSSM h or H should be discovered with a few tens of fbdiscovered with a few tens of fb-1-1
Studies of the CPX scenario have started.Studies of the CPX scenario have started.
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Backup SlidesBackup Slides
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Absolute couplings after Absolute couplings after assumptionsassumptions
SM-like Higgs assumptions:
Couplings to W and Z as in the SM.No new particles enter the loop for decay.
19-July-2005 ATLAS Sensitivity to SM and SUSY Higgs