klaus desch, report from the higgs working group, ecfa/desy workshop amsterdam, 4/4/03 1 report from...

Klaus Desch, Report from the Higgs Working Group, ECFA/DESY Workshop Amsterdam, 4/4/03 1

Report from the Higgs Working Group

Convenors:M.BattagliaK.DeschA.DjouadiE.GrossB.Kniehl

ECFA/DESYLC workshopNIKHEF,Amsterdam4/4/03

Fully simulated+reconstructed HZ event (BRAHMS)


Introduction

Framework:

Understanding the Nature of electro-weak symmetry breakingis one of the driving forces in the LC programmme

Existence of a light Higgs boson is favoured by experimental dataand most theoretical models

Exploration of the physics potential of the LC for Higgs physicshas three major motivations

1. Make the physics case

2. Give feedback to the design of the detector and the machine

3. Physics “R&D”: learn/don’t forget how to do the analyses


Introduction

TDR conclusion: Higgs mechnanism can be established in all essential elements

extended study not essential??? No.

Goals:- close remaining (but essential) corners- keep up with new theoretical ideas- further study relation to LHC- further study option (A. deRoeck’s 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


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


Profile of a SM-like Neutral Higgs Boson

Dominant production processes at LC:



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 alBoudjema et alJegerlehner et al

complicated task, e.g. “Pentagons”:sizable correction (o(10%))


Profile of a Higgs boson at the LC:

• Mass + Production Cross Sections

• Quantum Numbers

• Decay Branching Ratios

• Top Yukawa Coupling

• Double Higgsstrahlung (Self coupling)



Higgs Profile: Heavier SM Higgs

What, if Higgs mass (somewhat) larger, than EW precision data tell?

Study of

Most promising: final state

e e ZH ZWW and ZZZ e e ZH qqqq

only WW and ZZrelevant

measure width fromlineshape?

TDR: focus on mH=120,140,160 GeV


H

H

Results:

m =400 MeV(0.17%)

ΔΓ =830 MeV(25%)

ΔBR(WW)/BR(WW)=5%

ΔBR(ZZ)/BR(ZZ)=11%

Δσ(HZ)=4%

Profile of a SM-like Neutral Higgs BosonMass + Production Cross Section

N. Meyer

Also results for 200, 280, 320 GeV available

Reconstructed Higgs Mass (GeV)

for 500 fb-1@500 GeVmH=240 GeV


Higgs Profile: Quantum NumbersTDR: Spin from threshold scanTDR: CP from angular distributions of ZH

New Ideas:Spin from HZZCP from transverse polarisation correlations in H

Miller et al Was,WorekBowerImhof,KD

First estimate with detector simulation:

Observable: -acoplanarity:

> 8 separation between CP+ and CP-for 120 GeV Higgs (350GeV/1 ab-1)


Higgs Profile: Decay Modes

TDR:

for 500 fb-1 , m=120 GeV

BattagliaRichard et alSchreiber et al

Results (rel. errors)

bb 2.4%

cc 8.3%

gg 5.5%

6.0%

23.0%

WW 5.4%



New analysis of hadronic BR’s has startedusing newest tools (ZVTOP, SIMDET4, kinematic fit)

study dependence on vtx layoutkinematic selection (Zhadronsand Zleptons only) not yet optimal

preliminary numbers seem to~confirm TDR numbers

T.Kuhl,KD



TDR study: obtain BR’s from measuring

( )( )

( ) / ( )

HZ X Z

BR H XHZ H BR Z

Alternative approach: measure fraction of events withinan unbiased sample of events

disadvantage: smaller event sampleadvantage : binomial errors smaller than gaussian errors (one measurement instead of two)

H X HZ H

J-C.Brient

Results (rel. errors)

bb 1.9%

cc 8.1%

gg 4.8%

7.1%

35.0%

WW 3.6%500 fb-1@350 GeVmH =120 GeV


Higgs Profile: Rare Decay Modes

- rises with large number Higgs bosons at 800 GeV- test of ‘lepton universality in Higgs sector’- select events with two muons andmissing energy: clean signature- cut on recoil mass (remove ZZ)

ln s

H M.Battaglia

Result (rel. error)

BR(/BR() = 32 %ΔgH= 16 %for 1 ab-1@800 GeV


Higgs Profile: Rare Decay ModesM.Battaglia

as rare decay ( 160 GeV)HH bb m

Fusion(800GeV) preferred over Higgsstrahlung(350GeV)

Results for 1ab-1@800 GeV

mH(GeV) S/sqrt(B) BR(bb)/BR(bb)

180 10.5 11.5%

200 7.5 16.5%

220 4.1 27.5%



H ZSchreiber et al

Might add interesting informationIn case of anomalous coupling

Most promising channel: e e Z qq

Study for:

1500 ,1 s GeV ab

Results for 1ab-1@500 GeV

mH(GeV) S/sqrt(B) BR(Z)/BR(Z)

120 2.2 48%

140 4.4 27%

160 2.5 44%



Summary of rare decays:


Invisible Higgs DecaysMany SM extensions predict invisible Higgs Decays, e.g.:

• MSSM• 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:

0 0

1 1H

e e ZH qq E

1350 , 500

120,140,160

H

s GeV L fb

m GeV

missing mass

Signal(120)

M.Schumacher


Invisible Higgs Decays

Result:

M.Schumacher

Result for 500 fb-1@350 GeV (mH=120 GeV):ΔBR/BR(invis) = 10% for BR(invis) = 5%5σ observation down to BR = 2%


Top Yukawa coupling

4 channels analysed:

- extension to higher masses- and inclusion of HWW- ANN based selection- event-wise IP-probability tag- results confirmed with SIMDET4+ZVTOP

A.Gay


Top Yukawa coupling

Result: A.Gay

Precision on gttH

for 1ab-1@800 GeV

mH (GeV) gttH/gttH

120 7 %

140 17 %

170 13 %

200 15 %

for 5% syst. Backgrounduncertainty


Higgs Self Coupling

TDR:

P.Gay et al

13 % leads to 23 % (“dilution effect”)(for 1 ab-1 @ 500 GeV)


New Ideas for Higgs Self Coupling

Additional sensitivity from differential distributions to reduce the dilution:

Battaglia,Boos,Yao

/ 1.25SMHHH HHHg g

/ 0.5SMHHH HHHg g


MSSM Higgs Sector

• Higgs sector of MSSM: 5 physical Higgses: h0, H0, A0, H±

• phenomenology determined at tree level by 2 parameters: tanβ and mA.• Higher order corrections from 3rd generation fermions/sfermions important

Crucial prediction: mh<135 GeV

Heavy Higgs Bosons: mA∞ 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 notyet reached this goal. E.g. current theo. uncertainty in mh≈3 GeV

Djouadi et al

Degrassi et al


Additional MSSM Higgs Bosons

Analysis for e+e-HAbbbb at 500 GeV / 500 fb-1

-SIMDET4 -ZVTOP btagging -kinematic fit

Signals for sin()=1 and BR(H/Abb) = 85% :

Klimkovich



Results for e+e-HAbbbb at 500 GeV / 500 fb-1 :

mA mH (m) (m) σ*BR2 Resol(m/m)

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

observation up m(A)+m(H) ~ √s-30 GeV

Klimkovich

for sin()=1 and BR(H/Abb) = 85%



Raspereza

Analysis for e+e-HAbb/bb at 500 GeV / 500 fb-1

-SIMDET4 -ZVTOP btagging -kinematic fit -Lepton-ID

Signals for sin()=1 and BR(H/Abb) = 85% / BR(H/A) = 15% :



Results for e+e-HAbb/bb at 500 GeV / 500 fb-1 :

mA mH mA mH σ*BR2

HAbbσ*BR2

HAbb

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()=1 and BR(H/Abb) = 85% / BR(H/A) = 15%

mass resolution ~ 4-8 GeV


Charged Higgs

Battaglia,Ferrari,Kiiskinen,Maki

new: now with genuine tbtb background

At 800 GeV:5 discovery up to m=350 GeV


Theory: new calculations to beat kinematic limit

Weiglein et al2. Heavy neutral Higgses

couple ~cos() in decoupling limitnormally no WW-fusion cross section

Loop effects can enhance the cross section (a bit…) (somewhat) higher mass reach than for pair production

fb

fb

fbfb

mH(GeV)

tan

Heavy SUSY Higgses: pair production dominant mass reach limited explore (supressed) single production modes

1. Charged Higgs: Kniehl et alMoretti et al

e e tbH

e e H

e e W H

e+e-HMSSM

sqrt(s)=800 GeV


Constraining the MSSM Higgs sector

Ultimate goal: extract the underlying SUSY parameters from Higgs sector measurements from a global fit

We’re 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, BR’s also depend on

We should try to bring the bits and pieces together!

tan , , , ,..., ( ) t t btm m A m SUSY QCD

Am


Constraining the MSSM Higgs sector: examples

A.Sopczak et altanfrom H/A

Sensitivity to tan at 500 GeV/2 ab-1 (mA=200GeV)

tanfrom charged cross section slope Verzegnassi, Trimarchi

Gross,Heinemeyer,Battaglia, Richard

mA from bb/WW

more ideas:

SUSY corrections (mb) from bb/ Guasch, Hollik, Penaranda


Constraining the MSSM Higgs sector

Branching ratio deviation in constrained MSSM’s Ellis,Heinemeyer,Olive,Weiglein

(also results other constrained scenarios: NUHM, AMSB, GMSB)

mSugra


CP violation in the MSSM Higgs sectorFrank,Heinemeyer,Hollik,WeigleinPilaftsis,Wagner,Carena,Ellis

MSSM Higgs sector is CP conserving at tree levelCP violation enters through sfermion loop if couplings are complexLeads to 3 neutral Higgs mass eigenstates which are not CP eigenstates:


CP violation in the MSSM Higgs

T.KlimkovichMeasure masses and cross sections andscan parameter space assuming=10% and m=1GeV (conservative!)

Sensitivity to CPV parametersfrom a 3 parameter scan:


Extended Models

• 2HDM

• NMSSM

• Effects of Extra Dimensions on Higgs sector

• Higher Higgs representations

Krawczyk, Osland; Gunion

Huitu

Miller, Nevzorov, Zerwas

Wells,Hewett,Rizzo,Dominici,Ghosh,Gabrielli,Huitu


Extended Models: NMSSM

• NMSSM: additional Higgs singlet

• provides viable solution to -Problem of the MSSM

• Singlet introduces new U(1) Symmetry leading to massless

CP-odd Higgs (ruled out) 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

interesting phenomenology

Miller,Nevzorov,Zerwas


Extended Models: NMSSM

Example parameters:

e.g. 2 light CP-even Higgses with sizable HZZ coupling

need for study of LC sensitivity to the scenario and its parameters

Miller,Nevzorov,Zerwas


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 ‘tree level’ coupling to gluons

• Radion can mix with Higgs boson 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- mixing parameter


Extended Models: XD effects on Higgs sectorDominici,Battaglia,Gunion

LC ability of precise BR measurements allows to distingiushSM Higgs from mixed state (even if Radion itself is too heavy)

Red contours: deviation ofHbb BR > 2.5σ

Cyan Region: LHC H discoveryEnsured

Blue contours: LHC Radionobservation in ΦZZ

theoreticallynot allowed

theoreticallynot allowed

LC regions complementaryto LHC reach


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, /WW,…) or products (tt*bb)

• LHC+LC joint interpretation will be useful example (studied in LHC/LC group): tth)*BR(bb) @ LHC and BR(bb)@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-BR’s on mA point to mass region of interest


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 R&D

• Reexamine influence of machine parameters (Luminosity, Energy, Time structure, Backgrounds) on physics performance

• Become more realistic in simulation of our benchmark processes (recoil mass, BR’s, ZHH)

• Continue quantitative evaluation of the running options in , ee-e- modes (mass reach, light Higgs couplings, …)



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 it’s 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



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 general survey?)

General:

• International connections – exchange of ideas, codes, common projects etc can still improve!

• PhD theses on detector R&D are much nicer if accompanied by a physics applicability study (improve possibilities for publications of results?)


International Connections: an example

Ronan

Compare and understand differences in three regional simulation programs


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)!

klaus desch, report from the higgs working group, ecfa/desy workshop amsterdam, 4/4/03 1 report from...

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