Report from the Higgs Working Group

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Report from the Higgs Working Group
Convenors M.Battaglia K.Desch A.Djouadi E.Gross B
.Kniehl
ECFA/DESY LC workshop NIKHEF, Amsterdam 4/4/03
Fully simulatedreconstructed HZ event (BRAHMS)
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Introduction
Framework Understanding the Nature of
electro-weak symmetry breaking is one of the
driving forces in the LC programmme Existence of
a light Higgs boson is favoured by experimental
data and most theoretical models Exploration of
the physics potential of the LC for Higgs
physics has three major motivations 1. Make the
physics case 2. Give feedback to the design
of the detector and the
machine 3. Physics RD learn/dont forget
how to do the analyses
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Introduction

• TDR conclusion Higgs mechnanism can be
  established in all essential elements
• g extended study not essential??? No.
• Goals
• - close remaining (but essential) corners
• keep up with new theoretical ideas
• further study relation to LHC
• further study gg option (aA. deRoecks talk)
• become more realistic in experimental simulation
• Group was (and is) very active!
• 64 talks (35 exp/29 theo) in 4 workshops
• (sorry, I cannot mention all of them)
• Many (but certainly not all) goals achieved
  good progress

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Introduction

• Plan for this summary
• Profile of a SM-like neutral Higgs Boson
• MSSM additional Higgs Bosons and Sensitivity to
  Parameters
• Extended Models
• Relation to the LHC
• Thoughts about the Future
• Summary and Conclusion

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Profile of a SM-like Neutral Higgs Boson
Dominant production processes at LC
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Profile of a SM-like Neutral Higgs Boson
Status of calculations for SM Higgs production
and decay In general in very good shape Recent
addition full EW corrections to WW-fusion
Kniehl (LCWS02 review)
Denner et al Boudjema et al Jegerlehner et al
sizable correction (o(10))
complicated task, e.g. Pentagons
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Profile of a SM-like Neutral Higgs Boson

• Profile of a Higgs boson at the LC
• Mass Production Cross Sections
• Quantum Numbers
• Decay Branching Ratios
• Top Yukawa Coupling
• Double Higgsstrahlung (Self coupling)

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Higgs Profile Heavier SM Higgs
TDR focus on mH120,140,160 GeV
What, if Higgs mass (somewhat) larger, than EW
precision data tell?
only WW and ZZ relevant
measure width from lineshape?
Study of Most promising
final state
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Profile of a SM-like Neutral Higgs BosonMass
Production Cross Section
N. Meyer
for 500 fb-1_at_500 GeV mH240 GeV
Also results for 200, 280, 320 GeV available
Reconstructed Higgs Mass (GeV)
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Higgs Profile Quantum Numbers
TDR Spin from threshold scan TDR CP from
angular distributions of ZH New IdeasSpin from
HgZZ CP from transverse polarisation correlations
in Hgtt
Miller et al
Was,Worek Bower Imhof,KD
Observable rr-acoplanarity
First estimate with detector simulation
gt 8s separation between CP and CP- for 120 GeV
Higgs (350GeV/1 ab-1)
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Higgs Profile Decay Modes
Battaglia Richard et al Schreiber et al
TDR
Results (rel. errors) Results (rel. errors)
bb 2.4
cc 8.3
gg 5.5
tt 6.0
gg 23.0
WW 5.4
for 500 fb-1 , m120 GeV
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Higgs Profile Decay Modes
New analysis of hadronic BRs has started using
newest tools (ZVTOP, SIMDET4, kinematic fit)
T.Kuhl,KD
study dependence on vtx layout
kinematic selection (Zghadrons and Zgleptons
only) not yet optimal
preliminary numbers seem to confirm TDR numbers
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Higgs Profile Decay Modes
TDR study obtain BRs from measuring
J-C.Brient
Alternative approach measure fraction of
events within an unbiased sample of
events disadvantage smaller event
sample advantage binomial errors smaller
than gaussian errors (one
measurement instead of two)
Results (rel. errors)
bb 1.9
cc 8.1
gg 4.8
tt 7.1
gg 35.0
WW 3.6
500 fb-1_at_350 GeV mH 120 GeV
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Higgs Profile Rare Decay Modes
M.Battaglia

• - rises with
• a large number Higgs bosons at 800 GeV
• test of
• lepton universality in Higgs sector
• select events with two muons and
• missing energy clean signature
• - cut on recoil mass (remove ZZ)

Result (rel. error) DBR(mm)/BR(mm) 32 ?gHmm
16 for 1 ab-1_at_800 GeV
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Higgs Profile Rare Decay Modes
M.Battaglia
Fusion(800GeV) preferred over Higgsstrahlung(350Ge
V)
Results for 1ab-1_at_800 GeV Results for 1ab-1_at_800 GeV Results for 1ab-1_at_800 GeV
mH(GeV) S/sqrt(B) DBR(bb)/BR(bb)
180 10.5 11.5
200 7.5 16.5
220 4.1 27.5
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Higgs Profile Rare Decay Modes
Schreiber et al
Results for 1ab-1_at_500 GeV Results for 1ab-1_at_500 GeV Results for 1ab-1_at_500 GeV
mH(GeV) S/sqrt(B) DBR(gZ)/ BR(gZ)
120 2.2 48
140 4.4 27
160 2.5 44
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Higgs Profile Rare Decay Modes
Summary of rare decays
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Invisible Higgs Decays
M.Schumacher

• Many SM extensions predict invisible Higgs
  Decays, e.g.
• MSSM Hgc01c01
• Extra Dimensions
• Model with new singlets (NMSSM,Majoron Models)
• Stealthy Higgs
• TDR Estimate sensitivity from 1 BR(vis)
  BR(invis)
• New study explicit reconstruction in
• Assumptions

missing mass
Signal(120)
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Invisible Higgs Decays
M.Schumacher
Result
Result for 500 fb-1_at_350 GeV (mH120
GeV) ?BR/BR(invis) 10 for BR(invis) 5 5s
observation down to BR 2
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Top Yukawa coupling
A.Gay

• - extension to higher masses
• and inclusion of HgWW
• ANN based selection
• event-wise IP-probability tag
• results confirmed with SIMDET4ZVTOP

4 channels analysed
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Top Yukawa coupling
Result
A.Gay
Precision on gttH for 1ab-1_at_800 GeV Precision on gttH for 1ab-1_at_800 GeV
mH (GeV) DgttH/gttH
120 7
140 17
170 13
200 15
for 5 syst. Background uncertainty
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Higgs Self Coupling
P.Gay et al
TDR
Ds/s13 leads to DlHHH/lHHH23 (dilution
effect) (for 1 ab-1 _at_ 500 GeV)
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New Ideas for Higgs Self Coupling
Battaglia,Boos,Yao
Additional sensitivity from differential
distributions to reduce the dilution
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MSSM Higgs Sector

• Higgs sector of MSSM 5 physical Higgses h0,
  H0, A0, H
• phenomenology determined at tree level by 2
  parameters tanß and mA.
• Higher order corrections from 3rd generation
  fermions/sfermions important
• Crucial prediction mhlt135 GeV
• Heavy Higgs Bosons mAg8 decoupling limit, h is
  SM-like
• but H,A,H might
  as well be within reach of
• LC intense
  coupling regime
• Goal precise measurements of the observables
  (Higgs masses,
• couplings) to determine the fundamental
  SUSY parameters
• Needs high precision predictions of observables.
  Theory has not
• yet reached this goal. E.g. current theo.
  uncertainty in mh3 GeV

Djouadi et al
Degrassi et al
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Additional MSSM Higgs Bosons
Klimkovich

• Analysis for ee-gHAgbbbb at 500 GeV / 500 fb-1
• SIMDET4 -ZVTOP btagging -kinematic fit
• Signals for sin(b-a)1 and BR(H/Agbb) 85

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Additional MSSM Higgs Bosons
Klimkovich
Results for ee-gHAgbbbb at 500 GeV / 500 fb-1
mA mH D(Sm) D (dm) DsBR2 Resol(Sm/dm)
GeV GeV MeV MeV GeV
100 150 170 170 1.7 5.1/6.7
100 200 300 2.1 4. /8.7
100 250 590 3.0 4. /11.5
140 150 300 410 2.3 4.0/7.9
for sin(b-a)1 and BR(H/Agbb) 85
5s observation up m(A)m(H) vs-30 GeV
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Additional MSSM Higgs Bosons
Raspereza

• Analysis for ee-gHAgbbtt/ttbb at 500 GeV / 500
  fb-1
• SIMDET4 -ZVTOP btagging -kinematic fit
  -Lepton-ID
• Signals for sin(b-a)1 and BR(H/Agbb) 85 /
  BR(H/Agtt) 15

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Additional MSSM Higgs Bosons
Results for ee-gHAgbbtt/ttbb at 500 GeV / 500
fb-1
mA mH DmA DmH DsBR2 HAgbbtt Ds BR2 HAgttbb
GeV GeV MeV MeV
100 150 140 160 4.3 4.0
100 200 270 400 5.9 4.8
100 250 600 800 13.1 7.3
140 150 250 290 5.9 5.2
for sin(b-a)1 and BR(H/Agbb) 85 / BR(H/Agtt)
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mass resolution 4-8 GeV
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Charged Higgs
Battaglia,Ferrari,Kiiskinen,Maki
new now with genuine tbtb background
At 800 GeV 5s discovery up to m350 GeV
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Theory new calculations to beat kinematic limit
Heavy SUSY Higgses pair production dominant g
mass reach limited a explore (supressed) single
production modes
1. Charged Higgs
Kniehl et al Moretti et al
Weiglein et al

• 2. Heavy neutral Higgses
• couple cos(b-a) in decoupling limit
• normally no WW-fusion cross section
• Loop effects can enhance the cross section (a
  bit)
• g (somewhat) higher mass reach than for pair
  production

ee-gnnHMSSM sqrt(s)800 GeV
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Constraining the MSSM Higgs sector
Ultimate goal extract the underlying SUSY
parameters from Higgs sector measurements from a
global fit Were not there yet difficult task
since at higher orders, Higgs sectors depends on
many parameters (stop mixing etc.) Classical
example estimate from BR-measurement Yes!
But, BRs also depend on We should try to bring
the bits and pieces together!
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Constraining the MSSM Higgs sector examples
tanb from H/A
mA from bb/WW
A.Sopczak et al
Gross,Heinemeyer, Battaglia, Richard
Sensitivity to tanb at 500 GeV/2 ab-1 (mA200GeV)
more ideas
tanb from charged cross section slope
Verzegnassi, Trimarchi
SUSY corrections (Dmb) from bb/tt
Guasch, Hollik, Penaranda
Guasch,Hollik,Penaranda
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Constraining the MSSM Higgs sector
Ellis,Heinemeyer, Olive,Weiglein
Branching ratio deviation in constrained MSSMs
mSugra
(also results other constrained scenarios NUHM,
AMSB, GMSB)
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CP violation in the MSSM Higgs sector
Frank,Heinemeyer,Hollik,Weiglein Pilaftsis,Wagner,
Carena,Ellis
MSSM Higgs sector is CP conserving at tree
level CP violation enters through sfermion loop
if couplings are complex Leads to 3 neutral Higgs
mass eigenstates which are not CP eigenstates
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CP violation in the MSSM Higgs
Measure masses and cross sections and scan
parameter space assuming Ds10 and Dm1GeV
(conservative!)
T.Klimkovich
Sensitivity to CPV parameters from a 3 parameter
scan
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Extended Models

• 2HDM
• NMSSM
• Effects of Extra Dimensions on Higgs sector
• Higher Higgs representations

Krawczyk, Osland Gunion
Miller, Nevzorov, Zerwas
Wells, Hewett, Rizzo, Dominici, Ghosh, Gabrielli,
Huitu
Huitu
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Extended Models NMSSM
Miller, Nevzorov, Zerwas

• NMSSM additional Higgs singlet
• provides viable solution to m-Problem of the
  MSSM
• Singlet introduces new U(1) Symmetry leading to
  massless
• CP-odd Higgs (ruled out) g symmetry must be
  broken
• Phenomenology depends on how strongly the
  symmetry is broken (slightly broken symmetry
  preferred from RG running)
• Physical states 3 CP-even neutral
  2 CP-odd neutral
  2 charged
• a interesting phenomenology

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Extended Models NMSSM
Miller, Nevzorov, Zerwas
Example parameters
a e.g. 2 light CP-even Higgses with sizable HZZ
coupling a need for study of LC sensitivity to
the scenario and its parameters
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Extended Models XD effects on Higgs sector
Wells, Hewett, Rizzo, Dominici, Ghosh, Gabrielli,
Huitu

• Models with 5D localized gravity (RS model)
  appear to exhibit a scalar state (connected to
  excitations of force which stabilizes the
  distance between SM- and Planck-Brane The
  Radion
• Radion couples to trace of E-p-tensor ( very
  Higgs-like except for trace anomaly of QCD g
  tree level coupling to gluons
• Radion can mix with Higgs boson g two Higgs-like
  scalars with production cross sections and
  branching ratios different
• from SM Higgs
• Rather few model parameters
• - m(Higgs), m(Radion)
• - vev of Radion field L
• - mixing parameter x

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Extended Models XD effects on Higgs sector
Dominici, Battaglia, Gunion
LC ability of precise BR measurements allows to
distingiush SM Higgs from mixed state (even if
Radion itself is too heavy)
theoretically not allowed
Red contours deviation of Hgbb BR gt 2.5s Cyan
Region LHC H discovery Ensured Blue contours
LHC Radion observation in FgZZ
LC regions complementary to LHC reach
theoretically not allowed
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Relation to the LHC

• biggest asset of LC Higgs measurements model
  independence!
• LHC studies (also) improved since TESLA TDR
• (e.g. VBF channels allow o(10) measurement of
  various
• coupling ratios (WW/ZZ, tt/WW,) or products
  (ttbb)
• LHCLC joint interpretation will be useful
• example (studied in LHC/LC group)
• s(tth)BR(bb) _at_ LHC and BR(bb)_at_LC500 allows
  reasonable
• top Yukawa coupling measurement
• Light Higgs precision o(1) measurements can
  guide LHC
• studies when simultaneous running is ensured
• example sensitivity of h-BRs on mA g point to
  mass region
• of interest

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Thoughts About The Future

• What are the goals for a Higgs working group in
  the next 2 years??
• Experimental
• Physics studies as crucial input to detector RD
• Reexamine influence of machine parameters
  (Luminosity, Energy,
• Time structure, Backgrounds) on physics
  performance
• Become more realistic in simulation of our
  benchmark processes
• (recoil mass, BRs, ZHH)
• Continue quantitative evaluation of the running
  options
• in gg, eg, e-e- modes (mass reach, light Higgs
  couplings, )

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Thoughts About The Future

• Facing Experimental Reality
• full simulation (BRAHMS/MOKKA) is now really
  possible for physics studies
• development of appropriate analysis tools might
  take more time
• than the actual physics study (Kin.Fitting,
  Lepton-ID (esp. t)
• algorithms, ISR/BS photon ID, B-tagging, etc.
  etc.) but its
• worth the effort!
• Study the dependency of physics observables as a
  function
• of detector/machine parameters (First examples
  are arriving,
• we clearly need more)

see e.g. V.Saveliev
see e.g. T.Kuhl
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Thoughts About The Future

• Theory
• match experimental and theoretical precision.
  Identify, where particular effort is needed
• Watch new theoretical ideas (models with
  modified H coupling
• now easy to explore g general survey?)
• General
• International connections exchange of ideas,
  codes, common projects etc can still improve!
• PhD theses on detector RD
• are much nicer if accompanied by a physics
  applicability study
• (improve possibilities for publications of
  results?)

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International Connections an example
Ronan
Compare and understand differences in three
regional simulation programs
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Summary and Conclusions

• Higgs physics is a major pillar of the LC
  physics case
• This case has been further strengthened
• - higher masses carefully studied
• - rare Higgs decays
• - heavy SUSY Higgs Bosons
• - extraction of SUSY parameters from Higgs
  sector
• - sensitivity to extended models
• Studies with increased realism in the simulation
  have started They need be continued to give
  credible input to detector and machine design
• No reason to slow down only an active
  community is able to plan and realize the
  experiment(s)!