Higgs PhysicsHiggs Physics
with ATLASwith ATLAS Markus Schumacher, Bonn University
Seminar über Teilchenphysik, Wuppertal, November 10th 2005
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 2
Outline
the Higgs Mechanism and SM Higgs phenomenology at LHC
discovery potential for SM Higgs boson
investigation of the Higgs boson profile
phenomenology of SUSY Higgs bosons
discovery potential for MSSM Higgs bosons
discriminating the SM from extended Higgs sectors
conclusion and outlook
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 3
The Higgs Mechanism in the Nut Shell
consistent description of nature seems to be based on gauge symmetry
SU(2)LxU(1) gauge symmetry no masses for W and Z and fermions „ad hoc“ mass terms spoil
The problem:
The „standard“ solution:
new doublet of complex scalar fields
with appropiately choosen potential V
vacuum spontaneously breaks gauge symmetry
one new particle: the Higgs boson H
= v + H
• renormalisibilty no precise calculation of observables
• high energy behaviour WLWL scattering violates unitarity at ECM~1.2 TeV
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 4
Mass generation and Higgs couplings: = v + H
effective mass = friction of particles
with omnipresent „Äther“
v =247 GeVx
fermion
gf
mf ~ gf v Yukawa coupling
MV ~ g v gauge coupling
x x
W/Z boson
g gauge
Interaction of particles with v=247 GeV
Fermions gf ~ mf / v
W/Z Bosons: gV ~ 2 MV / v
Interaction of particles with Higgs H
fermion
gf
x
W/Z boson
g gauge
Higgs
Higgs v
2
2VVH coupling ~ vev
only present after EWSB breaking !!!
1 unknown parameter in SM: the mass of the Higgs boson
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 5
50 100 200 100010-3
10-2
10-1
100
bb cc tt gg WW ZZ
Bra
nchi
ng r
atio (Higgs
)
mH (GeV)
bb
WW
ZZ
tt
ccgg
Higgs Boson Decays in SM
for M<135 GeV: H bb, dominant
for M>135 GeV: H WW, ZZ dominant
tiny: H also important
HDECAY: Djouadi, Spira et al.
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 6
Status of SM Higgs Searches I: LEP
MH < 186 GeV
at 95% CL ,mtop=172 GeV
(MH<216 GeV for mtop=175 GeV)
MH<114.4 GeVexcluded at 95% CL
Direct search:
Electroweak fit:
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 7
Status of SM Higgs Searches II: TEVATRON
Expected sensitivity:
95% CL exclusion up to 130 GeV with 4fb-1 per experiment
3 sigma evidence up to 130 GeV with 8fb-1 per experiment
Current sensitivity::
Cross section limits at level of
~ 10 x SM cross section
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 8
1) mass
2) quantum numbers:
spin and CP
3) BRs, total width, couplings
4) self coupling at SLHC
Higgs Physics at LHC
discovery of 1 neutral scalar Higgs boson
(determination of mass, spin, CP)
discrimination between SM and extended Higgs sectors
1) > 1 neutral Higgs boson
2) charged Higgs boson
3) exotic decay modes
e.g. H invisible
4) … … …
direct observation of
additional Higgs bosons
determination of Higgs profile:
deviations from SM prediction
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 9
LHC and ATLAS
LHC: proton proton collisions at ECM = 14 TEV, start in 2007
- low luminosity running: 1(2)x1033 /(cm2 s) 10(20) fb-1/year- high luminosity running: 1034/(cm2 s) 100 fb-1/year
A Toroidal LHC Aparatus •design optimised for low mass Higgs boson discovery:
• H2 photons, HZZ 4 leptons
anticipated M/MH ~ 1 % em.-calorimetry, spectrometer
• ttH, Hbb
b=60(50)% Rc>10 Rudsg>100 Si tracking detectors• Htau tau, WWll, VBF prod. missing E. resolution, hermiticity, forward jets calorimetry to = 5
MC studies with fast simulation of ATLAS detector key performance numbers from full sim.: b/tau/jet/el.// identification, isolation criteria, jet veto, mass resolutions, trigger efficiencies, …
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 10
Production of the SM Higgs Boson at LHC
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 11
QCD corrections and Knowledge of Cross Sections
K = NNLO/LO~2
= 15% from scale variations
error from PDF uncertainty ~10%
Caveat: scale variations may underestimate the uncertainties!
ttH: K ~ 1.2 ~ 15% WH/ZH: K~1.3 to1.4 ~7%
VBF: K ~ 1.1 ~ 4% + uncertainties from PDF (5 to 15%)
but: rarely MC at NLO avaiable (except gluon gluon fusion)
background: NLO calculations often not avaiable
need background estimate from data
ATLAS policy: use K=1 for signal
e.g.: Gluon Gluon Fusion
Harlander et al.
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 12
Cross sections for Background Processes
Higgs 150 GeV: S/B <= 10-10
overwhelming background
trigger: 10-7 reduction
on leptons, photons, missing E
p pqq
q
p pqq
H
WW
l
l
Background: mainly QCD driven
Signal: often electroweak interaction
photons, leptons, …
q
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 13
Discovery Potential for light SM Higgs boson
discovery channels
GGF: H GGF: H ZZ 4l+-
GGF: HWW2(l)
ttH: H bb
VBF: H
VBF: H WW For MH>300 GeV also:
VBF: H ZZ ll
VBF: WW lqq
no fully hadronic final states: eg. GGF, VBF: Hbb
Higgs Boson mass reconstruction possible?
background controlable (S/B), estimate from data possible?
excl
ud
ed b
y L
EP
For MH>330 GeV also:
VBF: H ZZ ll
VBF: WW lqq
excl
ud
ed b
y L
EP
since 2000
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 14
H 2 Photons
ATLAS
signature: two high Pt background: irreducible pp +x
reducible ppj, jj, …
exp issues (mainly for ECAL):
, l+-, 0 separation (jet fake rate 10-4)
- energy scale, angular resolution
- conversions/dead material
mass resolution M: ~1%
precise background estimate
from sidebands (O(0.1%))
S/BG ~ 1/20
ATLAS 100fb-1
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 15
Gluon Fusion: H ZZ(*)4 Leptons
signature:
4 high pt isolated leptons
1(2) dilepton mass ~ MZ
irreducible BG: ZZ
mass reconstruction
reducible BG:
tt, Zbb 4 leptons
rejection via
lepton isolation and b-vetoATLAS TDR
good mass resolution M: ~1%
small and flat background easy estimate from data
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 16
Gluon Fusion: H WW l l
ATLAS
M=170GeV
L=30fb-1
signature:
- 2 high pt leptons + large missing ET
- lepton spin corrleations
- no mass peak transverse mass
transverse mass
BG: WW, WZ, tt
lepton iso., missing E resolution
jet (b-jet) veto against tt
BG estimate in data from ll
NLO effect on spin corr.
ggWW contribution signal like
Dührssen, prel.
ll
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 17
ttH with Hbb
mass resolution M: ~ 15%
50% correct bb pairings
very difficult background estimate from
data with exp. uncertainty ~ O(10%)
normalisation from side band
shape from „re-tagged“ ttjj sample
reducible BG: tt+jets, W+jets b-tagging
irreducible BG: ttbb reconstruct mass peak
exp. issue: full reconstruction of ttH final state combinatorics !!! need good b-tagging + jet / missing energy performance
S/BG ~ 1/6
30 fb-1
only channel to see Hbb
ATLAS
signature: 1 lepton, missing energy
6 jets of which 4 b-tagged
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 18
Vector Boson Fusion: ppqqH
Jet
Jet
signature:
-2 forward jets with
large rapidity gap
- only Higgs decay products in central part of detector
Forward tagging jets
Higgs Decay
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 19
Vector Boson Fusion: ppqqH
2 forward tagging jets with rapidity gap:
pT>20GeV
forward jet reconstruction
ATLASHigh Lumi
Low Lumi
jet-veto fake rate due to pile up
ATLAS
theory questions:
jet distributions at NLO?
esp. direction of 3rd jet?
efficieny of central jet veto?need NLO MC generator
for signal and BG
experimental issues:
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 20
signature: tagging jets +
- 2 high pt leptons + large missing ET
- lepton spin corrleations (spin10)
- no mass peak transverse mass
Weak Boson Fusion: HWWll (lqq)
tt, Wt, WWjj, ...
backgrounds:
HWWeATLAS
10 fb-1MH=160 GeV
S/BG ~ 3.5/1 BG uncertainty ~ 10 %
shape from MC
normalisation from side bands in
MT and ll
central jet vetob-veto
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 21
ATLAS
He
Vector Boson Fusion: H tau tau ll 4 (l had 3 )
mass resolution ~ 10%
determined by missing E. resolution BG uncertainty ~ 5 to 10%
for MH > 125 GeV: flat sideband
for MH < 125 normalisation from Z peak
30 fb-1
MH=120 GeV
signature: tagging jets +
- 2 high pt leptons + large missing ET
- mass reconstruction despite 4 in collinear approximation
backgrounds: Zjj, tt
S/BG ~ 1 to 2 / 1
central jet veto
reconstructionof m
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 22
Vector Boson Fusion, Hestimate of BG shape from dataIdea: jjZandjjZ
look almost the same esp. in calos
same missing energy
only momenta different
Method: select Z events
randomise momenta
apply „normal“ mass reco.
PTmiss,final (GeV) M (GeV)
promising prel. results from ongoing diploma thesis in BN (M. Schmitz)
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 23
SM discovery potential depending on int. luminosity
excl
ud
ed b
y L
EP
discovery from LEP exclusion until 1 TeV
from combination of search channels with 15 fb-1 of well understood data
with individual search channels with 30 fb-1 of well understood data
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 24
Investigation of Higgs boson profile
1) Mass determines completly SM phenomenology
2) Spin and CP QN Is it a CP even scalar boson?
3) Couplings Is it responsible for mass generation?
test SM prediction with best accuracy
look for deviations hint towards new physics
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 25
Measurement of Higgs Boson Mass
1fb300L
ATLAS
M/M: 0.1% to 1%
Uncertainties considered:
“Indirect” from Likelihood fit to transverse mass spectrum: HWWllWHWWWlll
Direct from mass peak: HHbb HZZ4l
VBF with H or WW
not studied yet !
i) statistical
ii) absolute energy scale
0.1 (0.02) % for l,,1% for jets
iii) 5% on BG + signal for HWW
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 26
sensitivity through spin correlations of Higgs decay products
one possibility HZZ4 leptons
))(cos()(sin)( 22 1TLG
TL
TLR
Spin and CP Quantum Numbers: 0 even in SM
: angle btw. decay planes
:angle btw. leptons and Z
in Z rest frame
(Gottfried Jackson angle)
Higgs rest frame
observation of Hor ggH rules out Spin=1 (Young theorem)
L (T) ratio of longitudinal (tranverse) polarised Z bosons
100 fb-1
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 27
Spin and CP Quantum Numbers: discrimination power
alternative methods:
decay: H via spin correlations
production: i) ttH angle between t,t,H ii) VBF btw. tagging jets
discrimination dominated by for masses > 250 GeV
seperation power > 2 for all
spin, CP hypothesis and MH>200 GeV
currently under study:
- NLO effects
- verification with full sim. + all BGs
- lower masses HZZ*
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 28
Determination of Higgs boson couplings
Loop induced effective couplings:(sensitive to new physics)
Photon: g = gW “+“ gt “+“…
Gluon: g = gt “+“ gb “+“…
Hx
x
Born level couplings:
Fermions gf = mf / v
W/Z Bosons: gV = 2 MV / v2
couplings in production Hx= const x Hx and decay BR(Hyy) = Hy / tot experiment: rate = Nsig+NBG Nsig= L x efficiency x Hx x BR
need to know: luminosity, efficiency, background
Hx x BR ~ HX Hy
tot
prod decay
partial width: Hz ~ gHz2
tasks: - disentangle contribution from production and decay
- determine tot
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 29
ratios of BRs = ratios of = ratios of g, if only Born level couplings
W
totW
totWW
)BR(HWW)BR(H
VBF
VBF
→
→e.g.
WWHZH,
WWHWH,
WWHttH,
WWHVBF,
WWHGF,
BR)(
BR)(
BR)(
BR)(
BR)(
W
b
WWW
Z
9 fit parameters:
all rates can
be expressed
by those 9
parameters
H WW chosen as reference as best measured for MH>120 GeV
For 30fb-1 worse by factor 1.5 to 2
13 analysis used
Ratio of Partial Widths
including various exp. and theo. errors
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 30
Total Decay Width H
for MH>200 GeV, tot>1GeV
measurement from peak width in ZZ4 l
upper limit needs input from theory:
mild assumption: gV<gVSM
valid in models with only Higgs doublets and singlets
rate(VBF, HWW) ~ V2 / tot < (V
2 in SM)/ tot
tot< rate/(V2 in SM)
lower limit from observable rates:
tot > W+Z+t+g+....
for MH<200 GeV, tot<< mass resolution
no direct determination
have to use indirect constraints on tot
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 31
Absolute couplings with gV < gVSM constraint
coupling to W, Z, , b, t
g/g = ½ g2)/g2
inv for undetactable decays
e.g. c, gluons,newphoton (new), gluon (new):
non SM contribution to loops
g/g = ½ g2)/g2
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 32
MH2 = 2 =MPlanck
Motivation for Supersymmetry from Higgs Sector
Higgs problem in SM: large corrections to the mass of the Higgs-Boson
2
“solves” hierarchy problem: why v = 246 GeV << MPl=1019GeV ?
MH2 = (MSM-MSUSY)
2 2
W W+ HH
natural value ~ MPl electroweak fit MH~O(100GeV)
SUSY solution: - partner with spin difference by ½ cancel divergence exactly if same M- SUSY broken in nature, but hierarchy still fine if MSUSY~1 TeV
H H
-
SUSY breaking in MSSM: parametrised by 105 additional parameters too many constrained MSSM with 5 (6) additional parameters
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 33
The MSSM Higgs sector in a tiny Nut Shell SUSY: 2 Higgs doublets 5 physical bosons
real MSSM: 2 CP even h, H, 1 CP odd A, charged H+, H-
at Born level 2 parameters: tan, m A mh < MZ
large loop corrections from SUSY breaking parameters
mh < 133 GeV for mtop=175 GeV, MSUSY=1TeV
corrections depend on 5 SUSY parameters: Xt, M0 , M2, Mgluino,
fixed in the benchmark scenarios e.g. MHMAX scenario
maximal Mh conservative LEP exclusion
t b/ W/Z
h cossin -sincos sin()
H sinsin cos/cos cos()
A cot tan -----
gMSSM = gSM
• no coupling of A to W/Z
• small small BR(h,bb)
• large large BR(h,H,A,bb)
= mixing btw. CP-even neutral Higgs bosons
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 34
Discovery Potential in the tanversus MA Plane
LEP tan exclusion:
no exclusion for mt larger ~183 GeV !TEVATRON:
so far exclusion for tan > 50 MA<200GeV
calculations with FeynHiggs (Heinemeyer et al.)
no systematic uncertainties yet
main questions for ATLAS: 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?
4 CP conserving benchmark scenarios considered: Carena et al. , Eur.Phys.J.C26,601(2003)
1) MHMAX 2) No mixing 3) Gluophobic 4) small
conclusions the same due to to complementarity of search channels
Mtop=174.3 GeV
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 35
h or H observable
with 30 fb-1
Vector Boson Fusion: 30 fb-1
studied for MH>110GeV at low lumi running
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 36
Light Higgs Boson h
large area covered by several channels sure discovery and parameter
determination possible
small area uncovered @ mh ~ 95 GeV
300 fb-130 fb-1
VBF dominates observation
small area from bbh,H
for small Mh
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 37
Heavy Neutral Higgs Bosons
large tan: bbH/A, H/A
~ (tan)2
ATLAS 30fb-1
low mass<450GeV: lep. had.
trigger on lepton
large mass > 450GeV: also had. had.
larger rate, trigger on hard tau jets
Eff.(LV1TR)= 80% =95% offline selected events
Tau ID: eff(tau)=55% rejection(QCD)=2500
H/A
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 38
Overall Discovery Potential: 300 fb-1
at least one Higgs boson
observable for all parameters
in all CPC benchmark scenarios
significant area where only lightest Higgs boson h is observable
questions for future studies:
can SUSY decay modes
provide observation?
e.g.: H/A2 LSP + 4 lept.
ongoing study in BN (N. Möser)
similar results in other benchmark scenarios
VBF channels , H/Aonly used with 30fb-1
300 fb-1
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 39
ATLASprel.
300 fb-1
SM or Extended Higgs Sector e.g. Minimal SUSY ?
discrimination via rates from VBF
R = BR(h WW) BR(h )
assume Higgs mass well measured no systematic errors considered
compare expected
measurement of R in MSSM
with prediction from SM
for same value of MH
=|RMSSM-RSM|exp
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 40
The Higgs Sector in the CP Violating MSSM
mass eigenstates H1, H2, H3
<> CP eigenstates h,A,H
at Born level: CP symmetry conserved in Higgs sector
complex SUSY breaking parameters introduce new CP phases
mixing between neutral CP eigenstates
no a priori reason for real SUSY parameters complex pars. new sources of CP violation el.-weak baryogenesis in complex MSSM ok evade constraints from dipole moments via
cancellations of different terms or split SUSY
Why consider such scenarios?
M. Carena, M. Quiros, C.Wagner’98
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 41
Phenomenology in the CPX scenario
H1,H2, H3 couple to W,Z
all produced in VBF
H3
H2
H1
H2,H3 H1H1, ZH1,WW, ZZ
decays possible
no limit for mass of H1 from LEP
(compare CPC MSSM: Mh>MZ
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+-
LHWG-Note 2004-01
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 42
CP-Violating MSSM: Overall Discovery Potential
MH1: < 70 GeVMH2: 105 to 120 GeV
MH3: 140 to 180 GeV
small masses below 70 GeVnot yet studied in ATLAS
300 fb-1
most promising channel: tt bW bH+, H+W H1, H1bb
final state: 4b 2j l same as ttH, Hbb (study in Bonn)
revised studies for H2/3H1H1 also interesting
yet uncovered area size and location of „hole“ depends on Mtop and program for calculation
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 43
Very First look at new promising MC study
M H+ =135 GeV, MH1=54GeV, tan=4.8 (diploma thesis M. Lehmacher)
estimate of background seems difficults
coverage of hole area under study!
signal
ttjj
ttbb
t tH+ b W b H+W H1 H1bb
1 leptonic W decay lepton for trigger
reconstruct top quarks combinatorics
associate b quarks to H1, H+ MH1 and M H+
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 44
Conclusion and Outlook
Standard model: discovery of SM Higgs boson with 15 fb-1
• requires good understanding of whole detector• multiple channels with larger luminosity Higgs profile investigaton
CP conserving MSSM: at least one Higgs boson observable • only h observable in wedge area at intermediate tan• maybe Higgs to SUSY or SUSY to Higgs observable?• discrimination via Higgs parameter determination seems promising
CP violating MSSM: probably a „hole“ with current MC studies• promising MC studies on the way
more realistic MC studies: • influence of miscalibrated and misaligned detector• improved methods for background estimation from data• use of NLO calcluations and MCs for signal and background
additional extended models + seach channels:• CPV MSSM, NMSSM, 2HDM• Higgs SUSY, SUSYHiggs• VBF, Hbb (b-trigger at LV2), VBF,Hinv. (add. forward jet trigger)
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 45
Let‘s wait and work for Higgs boson discovery ….
Thanks for your attention!
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 46
Backup slides
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 47
Evidence for Spin 0 in H->WW->ll mode
between leptons
W from H opposite spins leptons same direction
+ add. BG normalisation
MT>175 GeVMT<175 GeV
Signal Region
Outside Signal Region
Background estimate for VBF, HWW
mT(ll) with (left) and w/o (right) lepton cuts
background estimation at level of 10% from data + shape from MC
ATLAS
Transverse mass
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 48
CP even Spin 0: Measurement of Rates
Simultaneous fit of signal rates x BR in all 13 channels
Takes into account: cross talk between channels (e.g. GF events selected in VBF analysis) statistical fluctuations detector effects: Lumi, eff. tau, b-, forward jet tagging, and e background estimates: sidebands + shape + theoretical prediction uncertainties to signal rate from PDFs and QCD corrections
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 49
Overview of 13 Channels used in new ATLAS Study
Production Decay Mass range
Gluon fusion
HHZZ4l HWW(*) l l
110 – 150 GeV 120 – 200 GeV 110 – 200 GeV
Vector Boson Fusion*
HH HWW(*)l lHZZ4l
110 – 150 GeV 110 – 150 GeV 110 – 190 GeV 110 – 200 GeV
ttH
HHbbHWWl l
110 – 120 GeV 110 – 140 GeV 120 – 200 GeV
WHHHWWl ll
110 – 120 GeV 150 – 190 GeV
ZH H 110 – 120 GeV* only studied for low lumi running, L= 30fb-1
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 50
Higgs invisible particles
need confirmation by full simulation study
VBF assumes trigger on forward jets, not yet implemented
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 51
Higgs self coupling
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 52
The four CPC Benchmark Scenarios
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 conservative LEP exclusion
Nomixing scenario small mh < 116 GeV difficult for LHC
theo. goal: harm discovery viagg h, h and hZZ4 l
theo. goal: harm discovery viaVBF, h tth, hbb
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 53
Signal and Background Rates
LO with CTEQ5L (no K-factors!)
running b-quark mass for bbh(/H/A) and gbtH+
1) SM production cross sections times MSSM correction factors (FH)
2) branching ratios from FeynHiggs
3) efficiencies and background expectations from documented MC studies
Mt= 175 GeV used for now
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 54
4) for part of MSSM parameter space: large tot MSSM = K SM
K =
Corrections to Expected Signal Rates
5) signal overlap due to mass degeneracy of Higgs bosons
count signal in mass window 1
= signal 1 + signal 2 in window 1
h
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 55
MC Studies with Discovery Potential
channel lumi mass range publication
VBF, HWW low M>110 GeV SN-ATLAS-2003-024
ttH, Hbb * low+high M>70GeV ATL-PHYS-2003-003
bbH/A low+high 70<M<135GeV
M> 120 GeV
ATL-PHYS-2002-021
ATL-PHYS-2000-005
bbH/Alep.had
had. had.
low
low
M >120 GeV
M > 450 GeV
ATL-PHYS-2000-001 ATL-PHYS-2003-009
ATL-PHYS-2003-003
WWll low+high 140<M <120GeV ATL_PHYS-2000-015
H low+high M > 70 GeV TDR
ZZ4l low+high M > 100 GeV TDR
AZhllbb, Hhhbb
low+high 60 <ML<130 100<MH<360
TDR TDR
H/Att low+high M > 350 GeV TDR
gbtH+-, H,tb low+high M >180 GeV SN-ATLAS-2002-017
ttbW bH+-, H+- low M < 170 GeV ATL-PHYS-2003-58/TDR
*ttH, Hbb at high. lumi see MSSM note
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 56
almost same conclusion
for all 4 CP conserving
benchmark scenarios
Vector Boson Fusion: 4 CPC scenarios
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 57
Light Higgs Boson h: 30 fb-1
difference mainly due to
different mh in same (tan,MA) point
( up to 17 GeV difference)
observable channels: VBF bbh h tth hbb
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 58
Small scenario, h: 30 fb-1
• covered by enhanced BR to gauge bosons
• complementarity of search channels
almost gurantees observation of h
•hole due to reduced branching ratio for H
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 59
Light Higgs Boson h: 300 fb-1 (VBF only 30 fb-1)
also hgg, hZZ4 leptons, tthbb contribute
large area covered by several channels
sure discovery and parameter determination possible
small area uncovered @ mh = 90 to 100 GeV hsensitive in gluophobic scenario due to Wh, tth production
Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 60
Charged Higgs Bosons
gbH+-t
H+-
tbqq
low mass: mH+-< mtop
ggttttH+-bWonly low lumi.
new:
Wqq
H+-
high mass: mH+-> mtop
transition region around mtop
needs revised experimental analysis
running bottom quark mass used
Xsec for gbtH+- from T. Plehn‘s program