ATLAS Sensitivity to Standard Model and SUSY Higgs Bosons
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Transcript of ATLAS Sensitivity to Standard Model and SUSY Higgs Bosons
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
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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
19-July-2005 ATLAS Sensitivity to SM and SUSY Higgs
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SM Higgs: SM Higgs: ATLAS Discovery PotentialATLAS Discovery Potential
19-July-2005 ATLAS Sensitivity to SM and SUSY Higgs
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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)
Intermediate mass: 115 < MH < 180GeVChallenging for MH < 130GeV
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115GeV Higgs: first year (10fb115GeV Higgs: first year (10fb-1-1))
Total S/ B : ~ 4.2 Systematic errors included
complete detector
H->H-> ttH-ttH->ttbb>ttbb
qqH-qqH->qq>qq
SS 150150 1515 ~10~10
BB 39003900 4545 ~10~10
S/BS/B 0.040.04 0.330.33
S/√BS/√B 2.42.4 2.22.2 ~2.7~2.7
• 3 Channels all around 2, large backgrounds.
• Quite challenging.
Large K-factor~2 not included
L=30fb-1
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115GeV Higgs: Experimental 115GeV Higgs: Experimental ChallengesChallenges
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
19-July-2005 ATLAS Sensitivity to SM and SUSY Higgs
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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.
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CPConserving Benchmark CPConserving Benchmark ScenariosScenarios
MHMAX scenario maximal mh < 135 GeV (Xt ~ sqrt(6)*MS)
Nomixing scenario small mh < 116 GeV (Xt = 0)
Examples:
At MA>>MZ or MA~Mh,max and tan>>1, the heavy bosons degenerate in mass while the h decouples at Mh~130 GeV (decoupling regime of MSSM)
Maximum Mh depends on stop mixing Xt
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Discovery potential in tanDiscovery potential in tan vs M vs MAA planeplane
LEP tan exclusion: no exclusion for mt larger ~183 GeV !
two expected data volumes
30 fb-1 @ low lumi
300 fb-1 = 30 fb-1@ low lumi.
+ 270fb-1 @high lumi
discovery = 5 sigma excess
using Poissonian statistics
no systematic uncertainties yet
Is at least 1 Higgs boson observable in the entire parameter space?
How many Higgs bosons can be observed?
Can the SM be discriminated from extended Higgs sectors?
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H,h Discovery Potential H,h Discovery Potential 30fb30fb-1-1
almost gurantees
discovery of at least one
h or H with 30 fb-1
studied for MH>110GeVat low lumi running
SM like h with 30 fb-1
ll4
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h Discovery Potential 30fbh Discovery Potential 30fb-1-1
In Maximal Mixing Scenario: VBF hcovers most of the MSSM plane with 30fb-1
The VBF hchannel is also important for other MSSM scenarios
VBF h
Experimental Challenge:
Missing Et Reconstruction
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at least one Higgs boson
observable for all parameters
(true not only for MHMAX)
significant area where only lightest Higgs boson h is observable
can SM be discriminated from
extended Higgs sector by
parameter determination?
similar results in other benchmark scenarios
VBF channels , H/Aonly used with 30fb-1
300 fb-1
Overall Discovery Potential: 300 Overall Discovery Potential: 300 fbfb-1-1
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SM vs MSSM Higgs SM vs MSSM Higgs discriminationdiscrimination
BR(h WW) BR(h )
estimate of sensitivity from rate measurements in VBF channels (30fb-1)
R =
300 fb-1
only statistical errors
assume Mh exactly known needs further study incl. sys. errors
compare expected measurement of R in MSSM with prediction from SM
=|RMSSM-RSM|exp
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The CP violating CPX The CP violating CPX scenarioscenario
maximise effect CPX scenario (Carena et al., Phys.Lett B495 155(2000))
arg(At)=arg(Ab)=arg(Mgluino)=90 degree
scan of Born level parameters: tan and MH+-
CP eigenstates h, A, H mix to mass eigenstates H1, H2, H3
CP conserving at Born level, but CP violation via complex At, Ab Mgl
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CPX PhenomenologyCPX PhenomenologyH1,H2,H3 coupling to W,Z
H3
H2
H1
H2,H3 H1H1, ZH1,WW, ZZ decays
sum rule:
i gi (ZZHi)
= gSM
no absolute limit on mass of H1 from LEP
strong dependence of excluded region
on value for mtop
on calculation used FeynHiggs vs CPH
2
2
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CPX scenario: overall discovery CPX scenario: overall discovery potentialpotential
MH1: < 70 GeVMH2: 105 to 120 GeV
MH3: 140 to 180 GeV
small masses below 70 GeVnot yet studied in ATLAS
FeynHiggs with Mt=175 GeV
OPAL exclusion for Mt=174.3GeV
small uncovered area at low MH+-
FeynHiggs and CPSUPERH calculations
300 fb-1
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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.
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4 CPConserving Benchmark 4 CPConserving Benchmark ScenariosScenarios Carena et al. , Eur.Phys.J.C26,601(2003)
Gluophobic scenario small gh,gluon mh < 119 GeV
Small scenario small ghbb and gh mh <123 GeV
MHMAX scenario maximal mh < 133 GeV
Nomixing scenario small mh < 116 GeV
Affects gluon fusion channels:gg h, h and hZZ4 l
Affects:VBF, h tth, hbb
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MSSM experimental inputsMSSM experimental inputschannelchannel lumi lumi Mass rangeMass range PublicationPublicationVBF, HVBF, HWWWW lowlow M>110 GeVM>110 GeV SN-ATLAS-2003-024SN-ATLAS-2003-024
ttH, HttH, Hbbbb low+higlow+highh
M>70GeVM>70GeV ATL-PHYS-2003-003ATL-PHYS-2003-003
bbH/AbbH/A low+higlow+highh
70<M<135GeV70<M<135GeV
M> 120 GeVM> 120 GeV
ATL-PHYS-2002-021ATL-PHYS-2002-021
ATL-PHYS-2000-005ATL-PHYS-2000-005
bbH/AbbH/Alep.had,lep.had,had.Hhad.Hadad
lowlow
lowlowM>120GeVM>120GeV
M > 450 GeVM > 450 GeV
ATL-PHYS-2000-001 ATL-PHYS-2000-001 ATL-PHYS-2003-008ATL-PHYS-2003-008
gbgbtH+-, HtH+-, H,tb,tb low+higlow+highh
M >180 GeVM >180 GeV SN-ATLAS-2002-017SN-ATLAS-2002-017
ttttbW bH+-, H+-bW bH+-, H+- lowlow M < 170 GeVM < 170 GeV ATL-PHYS-2003-58ATL-PHYS-2003-58
H/AH/A low+higlow+highh
M > 350 GeVM > 350 GeV TDRTDR
AAZhZhllbb, llbb, HHhhhhbbbb
low+higlow+highh
60 <ML<130 60 <ML<130 100<MH<360100<MH<360
TDR TDRTDR TDR
HH low+higlow+highh
M > 70 GeVM > 70 GeV TDRTDR
ZZZZ4l 4l low+higlow+highh
M > 100 GeVM > 100 GeV TDRTDR
WWWWllll low+higlow+highh
140<M 140<M <120GEV<120GEV
TDRTDR
WHWHllbbbb lowlow 70<M<130GeV70<M<130GeV TDRTDR